DOCIMACY, from the Greek Δοκιμαζω, I prove; (Docimasie, Fr.;Probierkunst, Germ.;) is the art by which the nature and proportions of an ore are determined. This analytical examination was originally conducted in the dry way, the metal being extracted from its mineralizers, by means of heat and certain fluxes. But this method was eventually found to be insufficient and even fallacious, especially when volatile metals were in question, or when the fluxes could absorb them. The latter circumstance became a very serious evil, whenever the object was to appreciate an ore that was to be worked at great expense. Bergmann first demonstrated, in an elaborate dissertation, that the humid analysis was much to be preferred; and since his time the dry way has been consecrated chiefly to the direction of metallurgic operations, or, at least, it has been employed merely in concert with the humid, in trials upon the small scale.After discovering an ore of some valuable metal, it is essential to ascertain if its quantity and state of combination will justify an adventurer in working the mine, and smelting its products. The metal is rarely found in a condition approaching to purity; it is often disseminated in a mineralizingganguefar more bulky than itself; and more frequently still it is combined with simple non-metallic substances, such as sulphur, carbon, chlorine, oxygen, and acids, more or less difficult to get rid of. In these compound states its distinctive characters are so altered, that it is not an easy task either to recognize its nature, or to decide if it can be smelted with advantage. The assayer, without neglecting any of the external characters of the ore, seeks to penetrate, so to speak, into its interior; he triturates it to an impalpable powder, and then subjects it to the decomposing action of powerful chemical reagents; sometimes with the aid of alkalies or salts appropriate to its nature, he employs the dry way by fire alone; at others, he calls in the solvent power of acids with a digesting heat; happy, if after a series of labours, long, varied, and intricate, he shall finally succeed in separating a notable proportion of one or more metals either in a pure state, or in a form of combination such, that from the amount of this known compound, he can infer, with precision, the quantity of fine metal, and thereby the probable value of the mine. The blow-pipe, skilfully applied, affords ready indications of the nature of the metallic constituents, and is therefore usually the preliminary test. The separation of the several constituents of the ore can be effected, however, only by a chemist, who joins to the most extensive knowledge of the habitudes of mineral substances, much experience, sagacity, and precision, in the conduct of analytical operations. Under the individual metals, as also in the articlesMetallurgy,Mines, andOres, I have endeavoured to present such a copious and correct detail of docimastic processes, as will serve to guide the intelligent student through this most mysterious labyrinth of nature and art.
DOCIMACY, from the Greek Δοκιμαζω, I prove; (Docimasie, Fr.;Probierkunst, Germ.;) is the art by which the nature and proportions of an ore are determined. This analytical examination was originally conducted in the dry way, the metal being extracted from its mineralizers, by means of heat and certain fluxes. But this method was eventually found to be insufficient and even fallacious, especially when volatile metals were in question, or when the fluxes could absorb them. The latter circumstance became a very serious evil, whenever the object was to appreciate an ore that was to be worked at great expense. Bergmann first demonstrated, in an elaborate dissertation, that the humid analysis was much to be preferred; and since his time the dry way has been consecrated chiefly to the direction of metallurgic operations, or, at least, it has been employed merely in concert with the humid, in trials upon the small scale.
After discovering an ore of some valuable metal, it is essential to ascertain if its quantity and state of combination will justify an adventurer in working the mine, and smelting its products. The metal is rarely found in a condition approaching to purity; it is often disseminated in a mineralizingganguefar more bulky than itself; and more frequently still it is combined with simple non-metallic substances, such as sulphur, carbon, chlorine, oxygen, and acids, more or less difficult to get rid of. In these compound states its distinctive characters are so altered, that it is not an easy task either to recognize its nature, or to decide if it can be smelted with advantage. The assayer, without neglecting any of the external characters of the ore, seeks to penetrate, so to speak, into its interior; he triturates it to an impalpable powder, and then subjects it to the decomposing action of powerful chemical reagents; sometimes with the aid of alkalies or salts appropriate to its nature, he employs the dry way by fire alone; at others, he calls in the solvent power of acids with a digesting heat; happy, if after a series of labours, long, varied, and intricate, he shall finally succeed in separating a notable proportion of one or more metals either in a pure state, or in a form of combination such, that from the amount of this known compound, he can infer, with precision, the quantity of fine metal, and thereby the probable value of the mine. The blow-pipe, skilfully applied, affords ready indications of the nature of the metallic constituents, and is therefore usually the preliminary test. The separation of the several constituents of the ore can be effected, however, only by a chemist, who joins to the most extensive knowledge of the habitudes of mineral substances, much experience, sagacity, and precision, in the conduct of analytical operations. Under the individual metals, as also in the articlesMetallurgy,Mines, andOres, I have endeavoured to present such a copious and correct detail of docimastic processes, as will serve to guide the intelligent student through this most mysterious labyrinth of nature and art.
DORNOCK, is a species of figured linen of stout fabric, which derives its name from a town in Scotland, where it was first manufactured for table-cloths. It is the most simple in pattern of all the varieties of the diaper or damask style, and therefore the goods are usually of coarse quality for common household wear. It receives the figure by reversing the flushing of the warp and woof at certain intervals, so as to form squares, or oblong rectangles upon the cloth. The most simple of these is a succession of alternate squares, forming an imitation of a checker board or mosaic work. The coarsest kinds are generally woven as tweels of three leaves, where every thread floats over two, and is intersected by the third in succession. Some of the finer are tweels of four or five leaves, but few of more; for the six and seven leaf tweels are seldom or never used, and the eight leaf tweel is confined almost exclusively to damask. SeeTextile Fabric.
DORNOCK, is a species of figured linen of stout fabric, which derives its name from a town in Scotland, where it was first manufactured for table-cloths. It is the most simple in pattern of all the varieties of the diaper or damask style, and therefore the goods are usually of coarse quality for common household wear. It receives the figure by reversing the flushing of the warp and woof at certain intervals, so as to form squares, or oblong rectangles upon the cloth. The most simple of these is a succession of alternate squares, forming an imitation of a checker board or mosaic work. The coarsest kinds are generally woven as tweels of three leaves, where every thread floats over two, and is intersected by the third in succession. Some of the finer are tweels of four or five leaves, but few of more; for the six and seven leaf tweels are seldom or never used, and the eight leaf tweel is confined almost exclusively to damask. SeeTextile Fabric.
DRAGON’S BLOOD; (Sang dracon, Fr.;Drachenblut, Germ.) is a resinous substance, which comes to us sometimes in small balls of the size of a pigeon’s egg, sometimes in rods, like the finger, and sometimes in irregular cakes. Its colour, in lump, is dark brown red; in powder, bright red; friable; of a shining fracture, sp. grav. 1·196. It contains a little benzoic acid, is insoluble in water, but dissolvesreadily in alcohol, ether, and oils. It is brought from the East Indies, Africa, South America, as the produce of several trees, theDracæna Draco, thePterocarpus santalinus, thePterocarpus Draco, and theCalamus Rotang.Dragon’s blood is used chiefly for tingeing spirit and turpentine varnishes, for preparing gold lacquer, for tooth tinctures and powders, for staining marble, &c. According to Herbenger, it consists of 9·07 parts of red resin, 2 of fat oil, 3 of benzoic acid, 1·6 of oxalate, and 3·7 of phosphate of lime.
DRAGON’S BLOOD; (Sang dracon, Fr.;Drachenblut, Germ.) is a resinous substance, which comes to us sometimes in small balls of the size of a pigeon’s egg, sometimes in rods, like the finger, and sometimes in irregular cakes. Its colour, in lump, is dark brown red; in powder, bright red; friable; of a shining fracture, sp. grav. 1·196. It contains a little benzoic acid, is insoluble in water, but dissolvesreadily in alcohol, ether, and oils. It is brought from the East Indies, Africa, South America, as the produce of several trees, theDracæna Draco, thePterocarpus santalinus, thePterocarpus Draco, and theCalamus Rotang.
Dragon’s blood is used chiefly for tingeing spirit and turpentine varnishes, for preparing gold lacquer, for tooth tinctures and powders, for staining marble, &c. According to Herbenger, it consists of 9·07 parts of red resin, 2 of fat oil, 3 of benzoic acid, 1·6 of oxalate, and 3·7 of phosphate of lime.
DRUGGET, is a coarse, but rather slight, woollen fabric, used for covering carpets, and as an article of clothing by females of the poorer classes. It is now-a-days nearly superseded by coarse cotton goods.Drying house
DRUGGET, is a coarse, but rather slight, woollen fabric, used for covering carpets, and as an article of clothing by females of the poorer classes. It is now-a-days nearly superseded by coarse cotton goods.
Drying house
DRYING HOUSE. An apartment fitted up in a peculiar manner for drying calicoes, and other textile fabrics. Mr. Southworth, of Sharples, a Lancashire bleacher, obtained a patent, in 1823, for the following ingenious arrangement, which has been since generally adopted, with certain modifications, in most of our extensive bleaching and printing works.Fig.363.is a section of the drying-house, whereais a furnace and boiler for the purpose of generating steam; it is furnished with a safety valve in the tubeb, at top, and from this tube the steam maincpasses down to the floor of the basement story. From this main, a series of steam-pipes, asd d, extend over the surface of the floor, and from them heat is intended to be diffused for the purpose of warming the drying-house.Along the middle of the building a strong beam of timbere e, extends, and is supported by cast-iron pillars; from this beam, to bearings on the side walls, a series of rails are carried in a cross direction, over which rails the wet cloth is to be hung in folds, and the steam or evaporation emitted in drying is allowed to escape through apertures or ventilators in the roof.The mode in which the cloth is delivered on to the rails, on either side of the beam, will be best understood by reference to the delivering carriage, which is shown, with its rollers partly in section.The wet cloth is first to be coiled upon a roller, and then placed in the carriage, as atf, with its pivots bearing upon inclined planes. The carriage is to be placed at the commencement of the rails, running upon the middle beam, and also upon the side-bearings or railways extending along the side walls of the building, parallel to and upon a level with the same beam. It is made to travel by means of an endless band passing over two riggers,gandh, infig.363., and over pulleys and a band-wheel attached to the carriage, as will be explained. The riggerg, which moves this endless band, is actuated by bevel geer, seen ati, which is put in motion by a pinion at the end of a revolving shaft leading from a steam engine.In the samefig.,k kis the endless band passing over a pulley under the band-wheel, and over the pulleyn, by which it will be perceived that the traversing of the band, as described, would cause these pulleys and wheels to revolve. On the axle of the band-wheelm, there is a drum against which the roll of wet clothfpresses, and as this drum revolves, the roll of wet cloth is, by its friction, made to turn in a contrary direction, and to deliver off the cloth on to the periphery of the drum, whence it passes over a roller and descends to the tails. Upon the end of the axle of theband-wheelm, there is a pinion which takes into the teeth of the large wheel, and upon the axle of this large wheel there is a pinion that actuates the intermediate wheel, which turns another toothed wheel. This last-mentioned toothed wheel takes into cogs upon the side railway, and hence, as the train of wheels moves round, the carriage to which the wheels are attached is slowly impelled forward.As soon as the wheels begin to move, and the carriage to advance, the wet cloth begins to uncoil, and to pass down over the first roller; a small roller attached to the carriage, as it passes over the rails in succession, holds the cloth against each rail for a short space of time, and prevents it from slipping, by which means the cloth descends in folds or loops between the rails, and is thereby made to hang in a series of folds or loops, as shown in the figure.It will be perceived that as the pivots of the cloth rollerfbear upon inclined planes, the roller will continually slide down as the cloth diminishes in bulk, keeping in contact with the drum, and delivering the cloth from the roller on to the several rails, as described.In order to stop the carriage in any part of its course, or to adjust any of the folds of the cloth, a man is usually placed upon the platform travelling with the carriage, over which he has perfect command. This apparatus may be also employed for taking the cloth when dried off the rails; in which case the carriage must be made to travel backwards, and by first guiding the end of the cloth on to the rollerf, and then putting the wheels in a retrograde motion, the cloth will be progressively coiled upon the rollerf, in a similar way to that by which it was uncoiled.
DRYING HOUSE. An apartment fitted up in a peculiar manner for drying calicoes, and other textile fabrics. Mr. Southworth, of Sharples, a Lancashire bleacher, obtained a patent, in 1823, for the following ingenious arrangement, which has been since generally adopted, with certain modifications, in most of our extensive bleaching and printing works.Fig.363.is a section of the drying-house, whereais a furnace and boiler for the purpose of generating steam; it is furnished with a safety valve in the tubeb, at top, and from this tube the steam maincpasses down to the floor of the basement story. From this main, a series of steam-pipes, asd d, extend over the surface of the floor, and from them heat is intended to be diffused for the purpose of warming the drying-house.
Along the middle of the building a strong beam of timbere e, extends, and is supported by cast-iron pillars; from this beam, to bearings on the side walls, a series of rails are carried in a cross direction, over which rails the wet cloth is to be hung in folds, and the steam or evaporation emitted in drying is allowed to escape through apertures or ventilators in the roof.
The mode in which the cloth is delivered on to the rails, on either side of the beam, will be best understood by reference to the delivering carriage, which is shown, with its rollers partly in section.
The wet cloth is first to be coiled upon a roller, and then placed in the carriage, as atf, with its pivots bearing upon inclined planes. The carriage is to be placed at the commencement of the rails, running upon the middle beam, and also upon the side-bearings or railways extending along the side walls of the building, parallel to and upon a level with the same beam. It is made to travel by means of an endless band passing over two riggers,gandh, infig.363., and over pulleys and a band-wheel attached to the carriage, as will be explained. The riggerg, which moves this endless band, is actuated by bevel geer, seen ati, which is put in motion by a pinion at the end of a revolving shaft leading from a steam engine.
In the samefig.,k kis the endless band passing over a pulley under the band-wheel, and over the pulleyn, by which it will be perceived that the traversing of the band, as described, would cause these pulleys and wheels to revolve. On the axle of the band-wheelm, there is a drum against which the roll of wet clothfpresses, and as this drum revolves, the roll of wet cloth is, by its friction, made to turn in a contrary direction, and to deliver off the cloth on to the periphery of the drum, whence it passes over a roller and descends to the tails. Upon the end of the axle of theband-wheelm, there is a pinion which takes into the teeth of the large wheel, and upon the axle of this large wheel there is a pinion that actuates the intermediate wheel, which turns another toothed wheel. This last-mentioned toothed wheel takes into cogs upon the side railway, and hence, as the train of wheels moves round, the carriage to which the wheels are attached is slowly impelled forward.
As soon as the wheels begin to move, and the carriage to advance, the wet cloth begins to uncoil, and to pass down over the first roller; a small roller attached to the carriage, as it passes over the rails in succession, holds the cloth against each rail for a short space of time, and prevents it from slipping, by which means the cloth descends in folds or loops between the rails, and is thereby made to hang in a series of folds or loops, as shown in the figure.
It will be perceived that as the pivots of the cloth rollerfbear upon inclined planes, the roller will continually slide down as the cloth diminishes in bulk, keeping in contact with the drum, and delivering the cloth from the roller on to the several rails, as described.
In order to stop the carriage in any part of its course, or to adjust any of the folds of the cloth, a man is usually placed upon the platform travelling with the carriage, over which he has perfect command. This apparatus may be also employed for taking the cloth when dried off the rails; in which case the carriage must be made to travel backwards, and by first guiding the end of the cloth on to the rollerf, and then putting the wheels in a retrograde motion, the cloth will be progressively coiled upon the rollerf, in a similar way to that by which it was uncoiled.
DUCTILITY, (Streckbarkeit, Germ.) is the property of being drawn out in length without breaking, possessed in a pre-eminent degree by gold and silver, as also by many other metals, by glass in the liquid state, and by many semifluid resinous and gummy substances. The spider and the silk-worm exhibit the finest natural exercise of ductility upon the peculiar viscid secretions from which they spin their threads. When a body can be readily extended in all directions under the hammer, it is said to be malleable, and when into fillets under the rolling press, it is said to be laminable.Table of the ductility and malleability of Metals.Metals ductileand malleablein alphabeticalorder.Brittle metalsinalphabeticalorder.Metals in theorder of theirwire-drawingductility.Metals in theorder of theirlaminableductility.Cadmium.Antimony.Gold.Gold.Copper.Arsenic.Silver.Silver.Gold.Bismuth.Platinum.Copper.Iron.Cerium. ?Iron.Tin.Iridium.Chromium.Copper.Platinum.Lead.Cobalt.Zinc.Lead.Magnesium.Columbium. ?Tin.Zinc.Mercury.Iridium.Lead.Iron.Nickel.Manganese.Nickel.Nickel.Osmium.Molybdenum.Palladium. ?Palladium. ?Palladium.Osmium.Cadmium. ?Cadmium. ?Platinum.Rhodium.Potassium.Tellurium.Silver.Titanium.Sodium.Tungsten.Tin.Uranium.Zinc.There appears to be therefore a real difference between ductility and malleability; for the metals which draw into the finest wire are not those which afford the thinnest leaves under the hammer or in the rolling press. Of this fact iron affords a good illustration. Among the metals permanent in the air, 17 are ductile and 16 are brittle. But the most ductile cannot be wire-drawn or laminated to any considerable extent without being annealed from time to time during the progress of the extension, or rather, the sliding of the particles alongside of each other, so as to loosen their lateral cohesion.
DUCTILITY, (Streckbarkeit, Germ.) is the property of being drawn out in length without breaking, possessed in a pre-eminent degree by gold and silver, as also by many other metals, by glass in the liquid state, and by many semifluid resinous and gummy substances. The spider and the silk-worm exhibit the finest natural exercise of ductility upon the peculiar viscid secretions from which they spin their threads. When a body can be readily extended in all directions under the hammer, it is said to be malleable, and when into fillets under the rolling press, it is said to be laminable.
Table of the ductility and malleability of Metals.
There appears to be therefore a real difference between ductility and malleability; for the metals which draw into the finest wire are not those which afford the thinnest leaves under the hammer or in the rolling press. Of this fact iron affords a good illustration. Among the metals permanent in the air, 17 are ductile and 16 are brittle. But the most ductile cannot be wire-drawn or laminated to any considerable extent without being annealed from time to time during the progress of the extension, or rather, the sliding of the particles alongside of each other, so as to loosen their lateral cohesion.
DUNGING, in calico-printing, is the application of a bath of cowdung, diffused through hot water, to cotton goods in a particular stage of the manufacture. Dunging and scouring are commonly alternated, and are two of the most important steps in the process. The operation of dunging has for its objects:—1. To determine the entire combination of the aluminous sub-salts with the stuffs, byseparating almost all the acetic acid which was not volatilized in the stove-drying of the mordant.2. To dissolve and carry off from the cloth a portion of the thickening matters.3. To separate from the cloth the part of the mordant that is uncombined, and merely mixed mechanically with the gum or starch.4. To prevent, by the peculiar action of the dung, the uncombined mordant, as well as the acetic acid with which the bath is apt to get loaded, from affecting the blank parts of the cloth, or being injurious to the mordant.The aluminous base or mordant on the cloth, more or less neutralized by the dunging, is next subjected to the dash-wheel or fulling mill, where by the stream of water the remainder of the thickening and other impurities are washed away.No very exact analysis has been made of cowdung. Morin’s, which is the most recent and elaborate, is as follows:—Water70·00Vegetable fibre24·08Green resin and fat acids1·52Undecomposed biliary matter0·60Peculiar extractive matter (bubuline)1·60Albumen0·40Biliary resin1·80According to M. Kœchlin’s practical knowledge on the great scale, it consists of a moist fibrous vegetable substance, which is animalized, and forms about one-tenth of its weight; 2. of albumen; 3. of animal mucus; 4. of a substance similar to bile; 5. of muriate of soda, muriate and acetate of ammonia, phosphate of lime and other salts; 6. of benzoin or musk.Probably the hot water in which the calico-printer diffuses the dung, exerts a powerful solvent action, and in proportion as the uncombined mordant floats in the bath it is precipitated by the albumen, the animal mucus, and the ammoniacal salts; but there is reason to think that the fibrous matter in part animalized or covered with animal matter, plays here the principal part; for the great affinity of this substance for the aluminous salts is well known.All practical men are aware that the affinity of cotton for alumina is increased by its combination with oil or animal substances, to such a degree as to take it from the dung bath; which would not be possible without this combination. It would therefore appear that the principal function of dunging is to hinder the uncombined mordant, diffused in the dung bath, from attaching itself to the unmordanted portion of the cloth, as already observed; for if we merely wished to abstract the thickening stuffs, or to complete by the removal of acetic acid the combination of the aluminous base with the goods, dung would not be required, for hot water would suffice. In fact, we may observe, that in such cases the first pieces passed through the boiler are fit for dyeing; but when a certain number have been passed through, the mordant now dissolved in the water is attracted to the white portions of the cloth, while the free acid impoverishes the mordanted parts, so that they cannot afford good dyes, and the blank spaces are tarnished.The cow dung may be in some measure replaced by bran, but not with perfect success. The former both answers the purpose better and is cheaper. The bran is only preferred for the most delicate yellows, for cochineal pinks and lilacs, to which the dung may sometimes impart a greenish cast. It is to be presumed that the action of the bran in this process has much analogy with that of the dung, and that the ligneous fibre is the most active constituent; with which the gluten and mucilage co-operate, no doubt, in seizing the aluminous salts.It seems to be ascertained that the mordant applied to the cloth does not combine entirely with it during the drying; that this combination is more or less perfect according to the strength of the mordants, and the circumstances of the drying; that the operation of dunging, or passing through hot water, completes the combination of the cloth with the aluminous base now insoluble in water; that this base may still contain a very minute quantity of acetic acid or sulphate of alumina; that a long ebullition in water impoverishes the mordant but a little; and that even then the liquid does not contain any perceptible quantity of acetate or subsulphate of alumina.The manner of immersing the goods, or passing them through the dung bath, is an important circumstance. They should be properly extended and free from folds, which is secured by a series of cylinders.The cistern is from 10 to 12 feet long, 41⁄2feet wide, and 6 or 8 feet deep. The piece passes alternately over the upper rollers and under rollers near the bottom. There are two main squeezing rollers at one end, which draw the cloth through between them. Whenever the goods come out of the bath they are put into the dash-wheel.The immersion should take place as fast as possible, for the moment the hot water penetrates the mordanted cloth, the acetic acid quits it; and, therefore, if the immersion was made slowly or one ply after another, the acid as well as the uncombined mordant become free, would spread their influence, and would have time to dissolve the aluminous subsalts now combined with the cloth; whence inequalities and impoverishment of the colours would ensue.It is difficult to determine the number of pieces which may be passed through a given quantity of dung and water. This depends upon the state of the mordants, whether they are strong or acid, and on the quantity of the surface covered with the figures. The number varies usually from 20 to 60 pieces, for from 240 to 300 gallons of water and 6 gallons of dung. The time of the immersion varies with the concentration of the mordants, and the nature of their thickening. The temperature must be regulated by the same circumstances; for starch or flour paste a much warmer bath is needed than for gum. The heat varies usually from 130° to 212° F. When the printing is heavy and the thickening is starch or flour, the goods are usually twice dunged, with two washings between the two dungs. A strong acid mordant is more difficult to dung and to wash than a neutral mordant, especially when it is to receive the madder dye. Sometimes a little chalk is added to the bath, when the goods have been padded in an acid mordant. Too much dung is injurious to weak mordants, as well as to pinks. It has also been remarked that a mordant when neutralized does not produce as brilliant tints, especially yellows. The latter are obtained of a finer shade when, instead of dunging, they are exposed for an hour in a stream of water, provided its temperature is not too low. In winter they are passed through a slightly chalky water, then washed at the wheel, and dyed in quercitron or weld.A very able and learned memoir upon this subject, by M. Penot, Professor of Chemistry, appeared in the Bulletin of the Society of Mulhausen, in October, 1834, with an ingenious commentary upon it, under the title of a Report by M. Camille Kœchlin, in March, 1835.Experience has proved that dunging is one of the most important steps in the process of calico printing, and that if it be not well performed the dyeing is good for nothing. Before we can assign its peculiar function to the dung in this case, we must know its composition. Fresh cow’s dung is commonly neutral when tested by litmus paper; but sometimes it is slightly alkaline, owing, probably, to some peculiarity in the food of the animal.The total constituents of 100 parts of cow dung are as follows: Water, 69·58; bitter matter, 0·74; sweet substance, 0·93; chlorophylle, 0·28; albumine, 0·63; muriate of soda, 0·08; sulphate of potash, 0·05; sulphate of lime, 0·25; carbonate of lime, 0·24; phosphate of lime, 0·46; carbonate of iron, 0·09; woody fibre, 26·39; silica, 0·14; loss, 0·14.In dunging calicoes the excess of uncombined mordant is in part attracted by the soluble matters of the cow’s dung, and forms an insoluble precipitate, which has no affinity for the cloth, especially in presence of the insoluble part of the dung, which strongly attracts alumina. The most important part which that insoluble matter plays, is to seize the excess of the mordants, in proportion as they are dissolved by the water of the bath, and thus to render their reaction upon the cloth impossible. It is only in the deposit, therefore, that the matters carried off from the cloth by the dung are to be found.M. Camille Kœchlin ascribes the action of cow dung chiefly to its albuminous constituent, combining with the alumina and iron, of the acetates of these bases dissolved by the hot water of the bath. The acids consequently set free, soon become evident by the test of litmus paper, after a few pieces are passed through, and require to be got rid of either by a fresh bath or by adding chalk to the old one. The dung thus serves also to fix the bases on the cloth, when used in moderation. It exercises likewise a disoxidating power on the iron mordant, and restores it to a state more fit to combine with colouring matter.
DUNGING, in calico-printing, is the application of a bath of cowdung, diffused through hot water, to cotton goods in a particular stage of the manufacture. Dunging and scouring are commonly alternated, and are two of the most important steps in the process. The operation of dunging has for its objects:—
1. To determine the entire combination of the aluminous sub-salts with the stuffs, byseparating almost all the acetic acid which was not volatilized in the stove-drying of the mordant.
2. To dissolve and carry off from the cloth a portion of the thickening matters.
3. To separate from the cloth the part of the mordant that is uncombined, and merely mixed mechanically with the gum or starch.
4. To prevent, by the peculiar action of the dung, the uncombined mordant, as well as the acetic acid with which the bath is apt to get loaded, from affecting the blank parts of the cloth, or being injurious to the mordant.
The aluminous base or mordant on the cloth, more or less neutralized by the dunging, is next subjected to the dash-wheel or fulling mill, where by the stream of water the remainder of the thickening and other impurities are washed away.
No very exact analysis has been made of cowdung. Morin’s, which is the most recent and elaborate, is as follows:—
According to M. Kœchlin’s practical knowledge on the great scale, it consists of a moist fibrous vegetable substance, which is animalized, and forms about one-tenth of its weight; 2. of albumen; 3. of animal mucus; 4. of a substance similar to bile; 5. of muriate of soda, muriate and acetate of ammonia, phosphate of lime and other salts; 6. of benzoin or musk.
Probably the hot water in which the calico-printer diffuses the dung, exerts a powerful solvent action, and in proportion as the uncombined mordant floats in the bath it is precipitated by the albumen, the animal mucus, and the ammoniacal salts; but there is reason to think that the fibrous matter in part animalized or covered with animal matter, plays here the principal part; for the great affinity of this substance for the aluminous salts is well known.
All practical men are aware that the affinity of cotton for alumina is increased by its combination with oil or animal substances, to such a degree as to take it from the dung bath; which would not be possible without this combination. It would therefore appear that the principal function of dunging is to hinder the uncombined mordant, diffused in the dung bath, from attaching itself to the unmordanted portion of the cloth, as already observed; for if we merely wished to abstract the thickening stuffs, or to complete by the removal of acetic acid the combination of the aluminous base with the goods, dung would not be required, for hot water would suffice. In fact, we may observe, that in such cases the first pieces passed through the boiler are fit for dyeing; but when a certain number have been passed through, the mordant now dissolved in the water is attracted to the white portions of the cloth, while the free acid impoverishes the mordanted parts, so that they cannot afford good dyes, and the blank spaces are tarnished.
The cow dung may be in some measure replaced by bran, but not with perfect success. The former both answers the purpose better and is cheaper. The bran is only preferred for the most delicate yellows, for cochineal pinks and lilacs, to which the dung may sometimes impart a greenish cast. It is to be presumed that the action of the bran in this process has much analogy with that of the dung, and that the ligneous fibre is the most active constituent; with which the gluten and mucilage co-operate, no doubt, in seizing the aluminous salts.
It seems to be ascertained that the mordant applied to the cloth does not combine entirely with it during the drying; that this combination is more or less perfect according to the strength of the mordants, and the circumstances of the drying; that the operation of dunging, or passing through hot water, completes the combination of the cloth with the aluminous base now insoluble in water; that this base may still contain a very minute quantity of acetic acid or sulphate of alumina; that a long ebullition in water impoverishes the mordant but a little; and that even then the liquid does not contain any perceptible quantity of acetate or subsulphate of alumina.
The manner of immersing the goods, or passing them through the dung bath, is an important circumstance. They should be properly extended and free from folds, which is secured by a series of cylinders.
The cistern is from 10 to 12 feet long, 41⁄2feet wide, and 6 or 8 feet deep. The piece passes alternately over the upper rollers and under rollers near the bottom. There are two main squeezing rollers at one end, which draw the cloth through between them. Whenever the goods come out of the bath they are put into the dash-wheel.The immersion should take place as fast as possible, for the moment the hot water penetrates the mordanted cloth, the acetic acid quits it; and, therefore, if the immersion was made slowly or one ply after another, the acid as well as the uncombined mordant become free, would spread their influence, and would have time to dissolve the aluminous subsalts now combined with the cloth; whence inequalities and impoverishment of the colours would ensue.
It is difficult to determine the number of pieces which may be passed through a given quantity of dung and water. This depends upon the state of the mordants, whether they are strong or acid, and on the quantity of the surface covered with the figures. The number varies usually from 20 to 60 pieces, for from 240 to 300 gallons of water and 6 gallons of dung. The time of the immersion varies with the concentration of the mordants, and the nature of their thickening. The temperature must be regulated by the same circumstances; for starch or flour paste a much warmer bath is needed than for gum. The heat varies usually from 130° to 212° F. When the printing is heavy and the thickening is starch or flour, the goods are usually twice dunged, with two washings between the two dungs. A strong acid mordant is more difficult to dung and to wash than a neutral mordant, especially when it is to receive the madder dye. Sometimes a little chalk is added to the bath, when the goods have been padded in an acid mordant. Too much dung is injurious to weak mordants, as well as to pinks. It has also been remarked that a mordant when neutralized does not produce as brilliant tints, especially yellows. The latter are obtained of a finer shade when, instead of dunging, they are exposed for an hour in a stream of water, provided its temperature is not too low. In winter they are passed through a slightly chalky water, then washed at the wheel, and dyed in quercitron or weld.
A very able and learned memoir upon this subject, by M. Penot, Professor of Chemistry, appeared in the Bulletin of the Society of Mulhausen, in October, 1834, with an ingenious commentary upon it, under the title of a Report by M. Camille Kœchlin, in March, 1835.
Experience has proved that dunging is one of the most important steps in the process of calico printing, and that if it be not well performed the dyeing is good for nothing. Before we can assign its peculiar function to the dung in this case, we must know its composition. Fresh cow’s dung is commonly neutral when tested by litmus paper; but sometimes it is slightly alkaline, owing, probably, to some peculiarity in the food of the animal.
The total constituents of 100 parts of cow dung are as follows: Water, 69·58; bitter matter, 0·74; sweet substance, 0·93; chlorophylle, 0·28; albumine, 0·63; muriate of soda, 0·08; sulphate of potash, 0·05; sulphate of lime, 0·25; carbonate of lime, 0·24; phosphate of lime, 0·46; carbonate of iron, 0·09; woody fibre, 26·39; silica, 0·14; loss, 0·14.
In dunging calicoes the excess of uncombined mordant is in part attracted by the soluble matters of the cow’s dung, and forms an insoluble precipitate, which has no affinity for the cloth, especially in presence of the insoluble part of the dung, which strongly attracts alumina. The most important part which that insoluble matter plays, is to seize the excess of the mordants, in proportion as they are dissolved by the water of the bath, and thus to render their reaction upon the cloth impossible. It is only in the deposit, therefore, that the matters carried off from the cloth by the dung are to be found.
M. Camille Kœchlin ascribes the action of cow dung chiefly to its albuminous constituent, combining with the alumina and iron, of the acetates of these bases dissolved by the hot water of the bath. The acids consequently set free, soon become evident by the test of litmus paper, after a few pieces are passed through, and require to be got rid of either by a fresh bath or by adding chalk to the old one. The dung thus serves also to fix the bases on the cloth, when used in moderation. It exercises likewise a disoxidating power on the iron mordant, and restores it to a state more fit to combine with colouring matter.
DYEING, (Teinture, Fr.;Färberei, Germ.) is the art of impregnating wool, silk, cotton, linen, hair, and skins, with colours not removable by washing, or the ordinary usage to which these fibrous bodies are exposed when worked up into articles of furniture or raiment. I shall here consider the general principles of the art, referring for the particular dyes, and peculiar treatment of the stuffs to be dyed, to the different tinctorial substances in their alphabetical places; such ascochineal,indigo,madder, &c.Dyeing is altogether a chemical process, and requires for its due explanation and practice an acquaintance with the properties of the elementary bodies, and the laws which regulate their combinations. It is true that many operations of this, as of other chemical arts, have been practised from the most antient times, long before any just views were entertained of the nature of the changes that took place. Mankind, equally in the rudest and most refined state, have always sought to gratify the love of distinctionby staining their dress sometimes even their skin, with gaudy colours. Moses speaks of raiment dyed blue, and purple, and scarlet, and of sheep-skins dyed red; circumstances which indicate no small degree of tinctorial skill. He enjoins purple stuffs for the works of the tabernacle and the vestments of the high priest.In the articleCalico Printing, I have shown from Pliny that the antient Egyptians cultivated that art with some degree of scientific precision, since they knew the use of mordants, or those substances which, though they may impart no colour themselves, yet enable white robes (candida vela) to absorb colouring drugs (colorem sorbendibus medicamentis). Tyre, however, was the nation of antiquity which made dyeing its chief occupation and the staple of its commerce. There is little doubt that purple, the sacred symbol of royal and sacerdotal dignity, was a colour discovered in that city, and that it contributed to its opulence and grandeur. Homer marks no less the value than the antiquity of this dye, by describing his heroes as arrayed in purple robes. Purple habits are mentioned among the presents made to Gideon by the Israelites from the spoils of the kings of Midian.The juice employed for communicating this dye was obtained from two different kinds of shell-fish, described by Pliny under the names ofpurpuraandbuccinum; and was extracted from a small vessel, or sac, in their throats, to the amount of only one drop from each animal. A darker and inferior colour was also procured by crushing the whole substance of the buccinum. A certain quantity of the juice collected from a vast number of shells being treated with sea-salt, was allowed to ripen for three days; after which it was diluted with five times its bulk of water, kept at a moderate heat for six days more, occasionally skimmed to separate the animal membranes, and when thus clarified was applied directly as a dye to white wool, previously prepared for this purpose by the action of lime-water, or of a species of lichen called fucus. Two operations were requisite to communicate the finest Tyrian purple; the first consisted in plunging the wool into the juice of the purpura; the second, into that of the buccinum. Fifty drachms of wool required one hundred of the former liquor, and two hundred of the latter. Sometimes a preliminary tint was given with coccus, the kermes of the present day, and the cloth received merely a finish from the precious animal juice. The colours, though probably not nearly so brilliant as those producible by our cochineal, seem to have been very durable, for Plutarch says, in hisLife of Alexander, (chap. 36.), that the Greeks found in the treasury of the king of Persia a large quantity of purple cloth, which was as beautiful as at first, though it was 190 years old.[26][26]‘Among other things, there was purple of Hermione (?) to the amount of five thousand talents.’ (Plutarch’s Lives, translated by Langhorne, Wrangham’s edition, vol. v. p. 240.) Horace celebrates the Laconian dye in the following lines:—Nec Laconicas mihiTrahunt honestæ purpuras clientæ.(Carm., lib. ii., Ode 18.)The difficulty of collecting the purple juice, and the tedious complication of the dyeing process, made the purple wool of Tyre so expensive at Rome that in the time of Augustus a pound of it cost nearly 30l.of our money.[27]Notwithstanding this enormous price, such was the wealth accumulated in that capital, that many of its leading citizens decorated themselves in purple attire, till the emperors arrogated to themselves the privilege of wearing purple, and prohibited its use to every other person. This prohibition operated so much to discourage this curious art as eventually to occasion its extinction, first in the western and then in the eastern empire, where, however, it existed in certain imperial manufactories till the eleventh century.[27]Pliny says that a pound of the double-dipped Tyrian purple was sold in Rome for a hundred crowns.Dyeing was little cultivated in antient Greece; the people of Athens wore generally woollen dresses of the natural colour. But the Romans must have bestowed some pains upon this art. In the games of the circus parties were distinguished by colours. Four of these are described by Pliny, the green, the orange, the grey, and the white. The following ingredients were used by their dyers. A crude native alum mixed with copperas, copperas itself, blue vitriol, alkanet, lichen rocellus, or archil, broom, madder, woad, nut-galls, the seeds of pomegranate, and of an Egyptian acacia.Gage, Cole, Plumier, Reaumur, and Duhamel have severally made researches concerning the colouring juices of shell-fish caught on various shores of the ocean, and have succeeded in forming a purple dye, but they found it much inferior to that furnished by other means. The juice of the buccinum is at first white; it becomes by exposure to air of a yellowish green bordering on blue; it afterwards reddens, and finally changes to a deep purple of considerable vivacity. These circumstances coincide with the minute description of the manner of catching the purple-dye shell-fish which we possess in the work of an eye-witness, Eudocia Macrembolitissa, daughter of the Emperor Constantine VIII., who lived in the eleventh century.The moderns have obtained from the New World several dye-drugs unknown to the antients; such as cochineal, quercitron, Brazil wood, logwood, annatto; and they havediscovered the art of using indigo as a dye, which the Romans knew only as a pigment. But the vast superiority of our dyes over those of former times must be ascribed principally to the employment of pure alum and solution of tin as mordants, either alone or mixed with other bases; substances which give to our common dye-stuffs remarkable depth, durability, and lustre. Another improvement in dyeing of more recent date is the application to textile substances of metallic compounds, such as Prussian blue, chrome yellow, manganese brown, &c.Indigo, the innoxious and beautiful product of an interesting tribe of tropical plants, which is adapted to form the most useful and substantial of all dyes, was actually denounced as a dangerous drug, and forbidden to be used, by our parliament in the reign of Queen Elizabeth. An act was passed authorizing searchers to burn both it and logwood in every dye-house where they could be found. This act remained in full force till the time of Charles II.; that is, for a great part of a century. A foreigner might have supposed that the legislators of England entertained such an affection for their native woad, with which their naked sires used to dye their skins in the old times, that they would allow no outlandish drug to come in competition with it. A most instructive book might be written illustrative of the evils inflicted upon arts, manufactures, and commerce, in consequence of the ignorance of the legislature.[28][28]Author, in Penny Cyclopedia.Colours are not, properly speaking, material; they are impressions which we receive from the rays of light reflected, in a decomposed state, by the surfaces of bodies. It is well known that a white sunbeam consists of an indeterminate number of differently coloured rays, which being separated by the refractive force of a glass prism, form the solar spectrum, an image distinguishable into seven sorts of rays; the red, orange, yellow, green, blue, indigo, and violet. Hence, when an opaque body appears coloured, for example, red, we say that it reflects the red rays only, or in greatest abundance, mixed with more or less of the white beam, which has escaped decomposition. According to this manner of viewing the colouring principle, the art of dyeing consists in fixing upon stuffs, by means of corpuscular attraction, substances which act upon light in a different manner from the surfaces of the stuffs themselves. The dyer ought, therefore, to be familiar with two principles of optics; the first relative to the mixture of colours, and the second to their simultaneous contrast.Whenever the different coloured rays, which have been separated by the prism, are totally reunited, they reproduce white light. It is evident, that in this composition of light, if some rays were left out, or if the coloured rays be not in a certain proportion, we should not have white light, but light of a certain colour. For example; if we separate the red rays from the light decomposed by a prism, the remaining coloured rays will form by their combination a peculiar bluish green. If we separate in like manner the orange rays, the remaining coloured rays will form by their combination a blue colour. If we separate from the decomposed prismatic light the rays of greenish yellow, the remaining coloured rays will form a violet. And if we separate the rays of yellow bordering on orange, the remaining coloured rays will form by their union an indigo colour.Thus we see that every coloured light has such a relation with another coloured light that, by uniting the first with the second, we reproduce white light; a relation which we express by saying that the one is the complement of the other. In this sense, red is the complementary colour of bluish green; orange, of blue; greenish yellow, of violet; and orange yellow, of indigo. If we mix the yellow ray with the red, we produce orange; the blue ray with the yellow, we produce green; and the blue with the red, we produce violet or indigo, according as there is more or less red relatively to the blue. But these tints are distinguishable from the orange, green, indigo, and violet of the solar spectrum, because when viewed through the prism they are reduced to their elementary component colours.If the dyer tries to realize the preceding results by the mixture of dyes, he will succeed only with a certain number of them. Thus, with red and yellow he can make orange; with blue and yellow, green; with blue and red, indigo or violet. These facts, the results of practice, have led him to conclude that there are only three primitive colours; the red, yellow, and blue. If he attempts to make a white, by applying red, yellow, and blue dyes in certain quantities to a white stuff, in imitation of the philosopher’s experiment on the synthesis of the sunbeam, far from succeeding, he will deviate still further from his purpose, since the stuff will by these dyes become so dark coloured, as to appear black.This fact must not, however, lead us to suppose that in every case where red, yellow, and blue are applied to white cloth, black is produced. In reality, when a little ultramarine, cobalt blue, Prussian blue, or indigo, is applied to goods with the view of giving them the best possible white, if only a certain proportion be used, the goods will appear whiter after this addition than before it. What happens in this case? The violet blueforms, with the brown yellow of the goods, a mixture tending to white, or less coloured than the yellow of the goods and the blue together were. For the same reason, a mixture of prussian blue and cochineal pink has been of late years used in the whitening or the azuring of silks, in preference to a pure blue; for on examining closely the colour of the silk to be neutralized, it was found by the relations of the complementary colours, that the violet was more suitable than the indigo blue formerly used. The dyer should know, that when he applies several different colouring matters to stuffs, as yellow and blue, for example, if they appear green, it is because the eye cannot distinguish the points which reflect the yellow from those which reflect the blue; and that, consequently, it is only where the distinction is not possible, that a mixture or combination appears. When we examine certain gray substances, such as hairs, feathers, &c., with the microscope, we see that the gray colour results from black points, disseminated over a colourless or slightly coloured surface. In reference to compound colours, this instrument might be used with advantage by the dyer.The dyer should be acquainted also with the law of the simultaneous contrast of colours. When the eye views two colours close alongside of each other, it sees them differing most in their optical composition, and in the height of their tone, when the two are not equally pale or full-bodied. They appear most different as to their optical composition, when the complementary of the one of them is added to the colour of the other. Thus, put a green zone alongside of an orange zone; the red colour complementary of green, being added to the orange, will make it appear redder; and in like manner the blue, complementary of orange, being added to the green, will make it appear more intensely blue. In order to appreciate these differences, let us take two green stripes and two orange stripes, placing one of the green stripes near one of the orange; then place the two others so that the green stripe may be at a distance from the other green stripe, but on the same side, and the orange at a distance from the other orange, also on the same side.As to the contrast in the height of the tone, we may satisfy ourselves by taking the tones No. 1. No. 2. No. 15. and No. 16. from a graduated pallet of reds: for example, by placing No. 2. and No. 15. close alongside, putting No. 1. at a distance from No. 2. on the same side, and No. 16. at a distance from No. 15. on the same side,—we shall see (if the pallet is sufficiently lowered in tone) No. 2. equal to No. 1., and No. 15. equal to No. 16.; whence it follows that No. 2., by the vicinity of No. 15., will appear to have lost some of its colour; while No. 15. will appear to have acquired colour. When black or gray figures are printed upon coloured grounds, these figures are of the colour complementary of the ground. Consequently, in order to judge of their colour, we must cut out spaces in a piece of gray or white paper, so as to allow the eye to see nothing but the figures; and if we wish to compare figures of the same colour, applied upon grounds of different colours, we can judge rightly of the figures only by insulating them from the grounds.The relations of dyeing with the principles of chemistry, constitute the theory of the art, properly speaking; this theory has for its basis, the knowledge—1. of the species of bodies which dyeing processes bring into contact; 2. of the circumstances in which these species act; 3. of the phenomena which appear during their action; and 4. of the properties of the coloured combinations which are produced. These generalities may be specified under the ten following heads:—1. The preparation of the stuffs to be dyed, whether fibres, yarn, or cloth; under the heads of ligneous matter, cotton, hemp, flax; and of the animal matters, silk and wool.2. The mutual action of these stuffs, and simple bodies.3. The mutual action of these stuffs, and acids.4. The mutual action of these stuffs, and salifiable bases, as alumina, &c.5. The mutual action of these stuffs, and salts.6. The mutual action of these stuffs, and neutral compounds not saline.7. The mutual action of these stuffs, and of one or more definite compounds.8. Of dyed stuffs considered in reference to the fastness of their colour, under the influence of heat, light, water, oxygen, air, boilings with soap, and reagents.9. Of dyeing, considered in its connections with chemistry.10. Of dyeing, considered in its relations with caloric, mechanics, hydraulics, and optics.1. The preparation of stuffs.The operations to which stuffs are subjected before dyeing, are intended—1. to separate from them any foreign matters; 2. to render them more apt to unite with the colouring tinctures which the dyer proposes to fix upon them, in order to give them a more agreeable, or more brilliant aspect, or to lessen their tendency to assume a soiled appearance by use, which white surfaces so readily do. The foreign matters are either naturally inherent in the stuffs, or added to them in the spinning, weaving, or othermanipulation of manufacture. The ligneous fibres must be freed from the coloured azotized varnish on their surface, from a yellow colouring matter in their substance, from some lime and iron, from chlorophylle or leaf-green, and from pectic acid; all natural combinations. Some of these principles require to be oxygenized, before alkaline lyes can cleanse them, as I have stated in the articleBleaching, which may be consulted in reference to this subject. See alsoSilkandWool. A weak bath of soda has the property of preparing wool for taking on a uniform dye, but it must be well rinsed and aired before being put into the dye-vat.2. Mutual action of stuffs, and simple bodies.Stuffs chemically considered being composed of three or four elements, already in a state of reciprocal saturation, have but a feeble attraction for simple substances. We know in fact, that the latter combine only with each other, or with binary compounds, and that in the greater number of cases where they exert an action upon more complete compounds, it is by disturbing the arrangement of their elements, and not by a resulting affinity with the whole together.3, 4. Although stuffs may in a general point of view be considered as neutral in relation to colouring reagents, yet experience shows that they are more disposed to combine with acid than with alkaline compounds; and that consequently their nature seems to be more alkaline than acid. By steeping dry wool or other stuff in a clean state in an alkaline or acid solution of known strength, and by testing the liquor after the stuff is taken out, we shall ascertain whether there be any real affinity between them, by the solution being rendered more dilute in consequence of the abstraction of alkaline or acid particles from it. Wool and silk thus immersed, abstract a portion of both sulphuric and muriatic acids; but cotton and flax imbibe the water, with the rejection of a portion of the acid. The acid may be again taken from the stuffs by washing them with a sufficient quantity of water.5. The affinity between saline bodies and stuffs may be ascertained in the same way as that of acids, by plunging the dry stuffs into solutions of the salts, and determining the density of the solution before the immersion, and after withdrawing the stuffs. Wool abstracts alum from its solution, but it gives it all out again to boiling water. The sulphates of protoxide of iron, of copper and zinc resemble alum in this respect. When silk is steeped for some time in solution of protosulphate of iron, it abstracts the oxide, gets thereby dyed, and leaves the solution acidulous. Wool put in contact with cream of tartar decomposes a portion of it; it absorbs the acid into its pores, and leaves a neutral salt in the liquor. The study of the action of salts upon stuffs is at the present day the foundation of the theory of dyeing; and some of them are employed immediately as dye-drugs.6. Mutual action of stuffs, and neutral compounds not saline.Several sulphurets, such as those of arsenic, lead, copper, antimony, tin, are susceptible of being applied to stuffs, and of dyeing them in a more or less fast manner. Indigo, hematine, breziline, carmine, and the peculiar colouring principles of many dyes belong to this division.7. Mutual action of goods with one or more definite compounds, and dye-stuffs.I shall consider here in a theoretical point of view, the most general results which a certain number of organic colouring matters present, when applied upon stuffs by the dyer.Indigo.This dye-drug, when tolerably good, contains half its weight of indigotine. The cold vat is prepared commonly with water, copperas, indigo, lime, or sometimes carbonate of soda, and is used almost exclusively for cotton and linen; immersion in acidulated water is occasionally had recourse to for removing a little oxide of iron which attaches itself to the cloth dyed in this vat.The indigo vat for wool and silk is mounted exclusively with indigo, good potashes of commerce, madder and bran. In this vat, the immediate principles with base of carbon and hydrogen, such as the extracts of madder and bran, perform the disoxidizing function of the copperas in the cold vat. The pastel vats require most skill and experience, in consequence of their complexity. The greatest difficulty occurs in keeping them in a good condition, because they vary progressively as the dyeing goes on, by the abstraction of the indigotine, and the modification of the fermentable matter employed to disoxygenate the indigo. The alkaline matter also changes by the action of the air. By the successive additions of indigo, alkali, &c., this vat becomes very difficult to manage with profit and success. The great affair of the dyer is the proper addition of lime; too much or too little being equally injurious.Sulphate of indigo or Saxon blue is used also to dye silk and wool. If the wools be ill sorted it will show their differences by the inequalities of the dye. Wool dyed in this bath put into water saturated with sulphuretted hydrogen, becomes soon colourless, owing to the disoxygenation of the indigo. The woollen cloth when exposed to the air for some time, resumes its blue colour, but not so intensely as before.The properties of hematine explain the mode of using logwood. When stuffs are dyed in the infusion or decoction of this wood, under the influence of a base which acts upon the hematine in the manner of an alkali, a blue dye bordering upon violet is obtained. Such is the process for dyeing cotton and wool a logwood blue by means of verdigris, crystallized acetate of copper, and acetate of alumina.When we dye a stuff yellow, red, or orange, we have always bright tints; with blue we may have a very dark shade, but somewhat violet; the proper black can be obtained only by using the three colours, blue, red, and yellow, in proper proportions. Hence we can explain how the tints of yellow, red, orange, blue, green, and violet, may be browned, by applying to them one or two colours which along with themselves would produce black; and also we may explain the nature of that variety of blacks and grays which seems to be indefinite. Nutgalls and sulphate of iron, so frequently employed for the black dye, give only a violet or bluish gray. The pyrolignite of iron, which contains a brown empyreumatic matter, gives to stuffs a brown tint, bordering upon greenish yellow in the pale hues, and to chestnut brown in the dark ones. By galling cotton and silk, and giving them a bath of pyrolignite of iron, we may after some alternations dye them black. Galls, logwood, and a salt of iron, produce merely a very deep violet blue; but by boiling and exposure to air, the hematate of iron is changed, becoming red-brown, and favours the production of black. Galls and salts of copper dye stuffs an olive drab, logwood and salts of copper a violet blue; hence their combination should produce a black. In using sumach as a substitute for galls, we should take into account the proportion of yellow matter it contains. When the best possible black is wanted upon wool, we must give the stuff a foundation of indigo, then pass it into a bath of logwood, sumach, and proto-sulphate of iron. The sumach may be replaced by one third of its weight of nutgalls.8. Of dyed stuffs considered in reference to the fastness of their colours, when exposed to water, light, heat, air, oxygen, boiling and reagents.Pure water without air has no action upon any properly dyed stuff.Heat favours the action of certain oxygenized bodies upon the carbonaceous and hydrogenous constituents of the stuff; as is seen with regard to chromic acid, and peroxide of manganese upon cotton goods. It promotes the solvent action of water, and it even affects some colours. Thus Prussian blue applied to silk, is reduced to peroxide of iron by long boiling.Light without contact of air affects very few dyes.Oxygen, especially in the nascent state, is very powerful upon dyes. SeeBleaching.The atmosphere in a somewhat moist state affects many dyes, at an elevated temperature. Silk dyed pink, with safflower, when heated to 400° F. becomes of a dirty white hue in the course of an hour. The violet of logwood upon alumed wool becomes of a dull brown at the same temperature in the same time. But both stand a heat of 300° F. Brazil red dye, turmeric, and weld yellow dyes display the same phenomena. These facts shew the great fixity of colours commonly deemed tender. The stuffs become affected to a certain degree, under the same circumstances as the dyes. The alterability even of indigo in the air is shewn in the wearing of pale blue clothes; in the dark blue cloth there is such a body of colour, that it resists proportionally longer; but the seams of coats exhibit the effect very distinctly. In silk window curtains, which have been long exposed to the air and light, the stuff is found to be decomposed as well as the colour.Boilingwas formerly prescribed in France as a test of fast dyes. It consisted in putting a sample of the dyed goods in boiling water, holding in solution a determinate quantity of alum, tartar, soap, and vinegar, &c. Dufay improved that barbarous test. He considered that fast-dyed cloth could be recognized by resisting an exposure of twelve hours to the sunshine of summer, and to the midnight dews; or of sixteen days in winter.In trying the stability of dyes, we may offer the following rules:—That every stuff should be exposed to the light and air; if it be intended to be worn abroad, it should be exposed also to the wind and rain; that carpets moreover should be subjected to friction and pulling, to prove their tenacity; and that cloths to be washed should be exposed to the action of hot water and soap.In examining a piece of dyed cotton goods, we may proceed as follows:—Suppose its colour to be orange-brown. We find first that it imparts no colour to boiling water; that protochloride of tin takes out its colour; that plunged into a solution of ferroprussiate of potash it becomes blue; and that a piece of it being burned, leaves a residuum of peroxide of iron; we may thence conclude that the dyeing matter is peroxide of iron.Suppose we have a blue stuff which may have been dyed either with indigo or with Prussian blue, and we wish to know what it will become in use. We inquire first into the nature of the blue. Hot water slightly alkaline will be coloured blue by it, ifit has been dyed with sulphate of indigo; it will not be coloured if it was dyed in the indigo vat, but it will become yellow by nitric acid. Boiling water, without becoming coloured itself, will destroy the Prussian blue dye; an alkaline water will convert its colour into an iron rust tint; nitric acid, which makes the indigo dye yellow, makes that of Prussian blue green. The liquor resulting from boiling alkaline water on the Prussian blue cloth, will convert sulphate of iron into Prussian blue.9. Division. Of dyeing viewed in its relation to chemistry.The phenomena of dyeing have been ascribed to very different causes; by some they were supposed to depend upon mechanical causes, and by others upon the forces from which chemical effects flow. Hellot, in conformity with the first mode of explanation, thought that the art of dyeing consisted essentially in opening the pores in order to admit colouring matters into them, and to fix them there by cooling, or by means of a mordant imagined to act like a cement.Dufay in 1737, Bergmann in 1776, Macquer in 1778, and Berthollet in 1790, had recourse to chemical affinities, to explain the fixation of the colouring principles upon stuffs, either without an intermedium, like indigo, walnut peels, annotto; or by the intervention of an acid, a salifiable base, or a salt, which were called mordants. When bodies present phenomena which we refer to an attraction uniting particles of the same nature, whether simple or compound, to form an aggregate, or to an affinity which unites the particles of different natures to form them into a chemical compound, these bodies are in apparent contact. This happens precisely in all the cases of the mutual action of bodies in an operation of dyeing; if their particles were not in apparent contact, there would be absolutely no change in their respective condition. When we see stuffs and metallic oxides in apparent contact, form a mutual union of greater or less force, we cannot therefore help referring it to affinity. We do not know how many dyes may be fixed upon the same piece of cloth; but in the operations of the dye-house sufficiently complex compounds are formed, since they are always stuffs, composed of three or four elements, which are combined with at least binary acid or basic compounds; with simple salts compounded themselves of two immediate principles at least binary; with double salts composed of two simple salts; and finally with organic dye-stuffs containing three or four elements. We may add that different species belonging to one of these classes, and different species belonging to different classes, may unite simultaneously with one stuff. The union of stuffs with colouring matters appears, in general, not to take place in definite proportions; though there are probably some exceptions.We may conclude this head by remarking, that, besides the stuff and the colouring matter, it is not necessary, in dyeing, to distinguish a third body, under the name ofmordant; for the idea of mordant does not rest upon any definite fact; the body to which this name has been given being essentially only one of the immediate principles of the coloured combination which we wish to fix upon the stuff.10. Division. Of dyeing in its relation with caloric, mechanics, hydraulics, pneumatics, and optics.Dyeing baths, or coppers, are heated directly by a furnace, or by means of steam conducted in a pipe from a boiler at a certain distance from the bath. In the first case, the vessels are almost always made of copper; only, in special cases, for the scarlet and some delicate silk dyes, of tin; in the second case, they are of copper, iron, or wood. A direct fire is more economical than heating steam pipes, where there is only one or two baths to heat, or where the labours are often suspended. Madder and indigo vats, when heated by steam, have it either admitted directly into the liquor, or made to circulate through pipes plunged into it, or between the copper and an exterior iron or wood case. Seethe endof this article.Every thing else being equal, dyeing with heat presents fewer difficulties towards obtaining an evenly colour, than dyeing in the cold; the reason of which may be found in the following facts:—The air adhering to the surface of stuffs, and that interposed between the fibres of their constituent yarns, is more easily extricated in a hot bath than a cold one, and thus allows the dye liquor to penetrate more easily into their interior: in the second place, the currents which take place in a hot bath, and which tend incessantly to render its contents uniform, by renewing continually the strata of liquid in contact with the stuff, contribute mainly to render the dyeing evenly. In cold dyeing, it is necessary to stir up the bath from time to time; and when goods are first put in, they must be carefully dipped, then taken out, pressed, and wrung, several times in succession till they be uniformly moistened.The mechanical relations are to be found in the apparatus employed for wincing, siring, and pressing the goods, as we have described underCalico PrintingandBandanna. The hydraulic relations refer to the wash-wheels and other similar apparatus, of which an account is given under the same articles. The optical relationshave been already considered. In the sequel of this article an automatic dyeing vat will be described.The extracts of solutions of native dye-stuffs may be divided into two classes, in reference to their habitudes with the oxygen of the atmosphere; such as continue essentially unaltered in the air, and such as suffer oxidation, and thereby precipitate a determinate colouring matter. The dyes contained in the watery infusions of the different vegetable and animal substances which do not belong to the second class, are feebly attached to their solvents, and quit them readily for any other bodies that possess an attraction for them. On this principle, a decoction of cochineal, logwood, brazil wood, or a solution of sulphate of indigo, by digestion with powdered bone black, lose their colour, in consequence of the colouring particles combining by a kind of capillary attraction with the porous carbon, without undergoing any change. The same thing happens when well-scoured wool is steeped in such coloured liquids; and the colours which the wool assumes by its attraction for the dye, is, with regard to most of the above coloured solutions, but feeble and fugitive, since the dye may be again abstracted by copious washing with simple water, whose attractive force therefore overcomes that of the wool. The aid of a high temperature, indeed, is requisite for the abstraction of the colour from the wool and the bone-black, probably by enlarging the size of the pores, and increasing the solvent power of the water.Those dye-baths, on the contrary, whose colouring matter is of the nature of extractive or apothème, form a faster combination with stuffs. Thus the yellow, fawn, and brown dyes, which contain tannin and extractive, become oxygenated by contact of air, and insoluble in water; by which means they can impart a durable dye. When wool is impregnated with decoctions of that kind, its pores get charged by capillarity, and when the liquid becomes oxygenated, they remain filled with a colour now become insoluble in water. A similar change to insolubility ensues when the yellow liquor of the indigo vat gets oxidized in the pores of cotton and wool, into which it had been introduced in a fluid state. The same change occurs when protosulphate of iron is converted into persulphate, with the deposition of an insoluble peroxide in the substance of the stuff. The change here effected by oxidation can, in other circumstances, be produced by acids which have the power of precipitating the dye-stuff in an insoluble state, as happens with decoction of fustic.Hence we perceive that the dyeing of fast colours rests upon the principle, that the colours dissolved in the vat, during their union with the stuff, should suffer such a change as to become insoluble in their former menstruum. The more this dye, as altered in its union with the stuff, can resist other menstrua or agents, the faster it will be. This is the essential difference between dyeing and painting; or applying a coat of pigment devoid of any true affinity for the surface.If we mix a clear infusion of a dye with a small quantity of a solution of an earthy or metallic salt, both in water, the limpid liquids soon become turbid, and there gradually subsides sooner or later, according to the nature of the mixture, a coloured precipitate, consisting of the altered dye united with a basic or subsalt. In this compound the colouring matter seems to act the part of an acid, which is saturated by a small quantity of the basis, or in its acid relationship is feeble, so that it can also combine with acids, being in reference to them a base. The decomposition of a salt, as alum, by dyes, is effected principally through the formation of an insoluble subsalt, with which the colour combines, while a supersalt remains in the bath, and modifies, by its solvent reaction, the shade of the dyed stuff. Dyed stuffs may be considered as composed of the fibrous body intimately associated with the colouring matter, the oxide, and acid, all three constituting a compound salt. Many persons have erroneously imagined, that dyed goods contained none of the acid employed in the dye bath; but they forget that even potash added to alum does not throw down the pure earthy basis, but a subsalt; and they should not ascribe to colouring matter a power of decomposition at all approaching to that of an alkali. Salts, containing strong acids, saturate a very large quantity of colouring matter, in proportion to their place in the scale of chemical equivalents. Mere bases, such as pure alumina, and pure oxide of tin, have no power of precipitating colouring matter; when they seem to do so, they always contain some acid.Such salts, therefore, as have a tendency to pass readily into the basic state, are peculiarly adapted to act as mordants in dyeing, and to form coloured lakes. Magnesia affords as fine a white powder as alumina, and answers equally well to dilute lakes, but its soluble salts cannot be employed to form lakes, because they do not pass into the basic state. This illustration is calculated to throw much light upon dyeing processes in general.The colour of the lake depends very much upon the nature of the acid, and the basis of the precipitating salt. If it be white, like alumina and oxide of tin, the lake will have, more or less, the colour of the dye, but brightened by the reflection of whitelight from the basis; while the difference of the acid occasions a difference in the hue. The coloured bases impart more or less of their colour to the lakes, not merely in virtue of their own tints, but of their chemical action upon the dye.Upon these principles a crimson precipitate is obtained from infusions of cochineal by alum and salt of tin, which becomes scarlet by the addition of tartar; by acetate of lead, a violet blue precipitate is obtained, which is durable in the air; by muriate of lime, a pink brown precipitate falls, which soon becomes black, and at last dirty green; by the solution of a ferruginous salt, the precipitates are dark violet, and black; and, in like manner, all other salts with earthy or metallic bases, afford diversities of shade with cochineal. If this dye stuff be dissolved in weak water of ammonia, and be precipitated with acetate of lead, a green lake is obtained, which, after some time, will become green on the surface by contact of air, but violet and blue beneath. Hence it appears, that the shade of colour of a lake depends upon the degree of oxidation or change of the colour caused by the acid of the precipitating salt, upon the degree of oxidation or colour of the oxide which enters into union with the dye, and upon its quantity in reference to that of the colouring principle.Such lakes are the difficultly soluble salts which constitute the dyeing materials of stuffs. Their particles, however, for the purposes of dyeing, must exist in a state of extremely fine division in the bath liquor, in order that they may penetrate along with it into the minute pores of textile fibres, and fill the cavities observed by means of the microscope in the filaments of wool, silk, cotton, and flax. I have examined these stuffs with an achromatic microscope, and find that when they are properly dyed with fast colours, the interior of their tubular texture is filled, or lined at least, with colouring matter. When the bath contains the colouring particles, so finely divided that they can pass through filtering paper, it is capable of dyeing; but if the infusion mixed with its mordant be flocculent and ready to subside, it is unfit for the purpose. In the latter case, the ingredients of the dye have already become aggregated into compounds too coherent and too gross for entering into combination with fibrous stuffs. Extractive matter and tannin are particularly liable to a change of this kind, by the prolonged action of heat in the bath. Hence also an alkaline solution of a colouring matter, affords no useful dye bath, when mixed with the solution of a salt having an earthy or metallic basis.These circumstances, which are of frequent occurrence in the dye-house, render it necessary always to have the laky matter in a somewhat soluble condition, and to effect its precipitation within the pores of the stuffs, by previously impregnating them with the saline solutions by the aid of heat, which facilitates their introduction.When a mordant is applied to any stuff, the portion of it remaining upon the surface of the fibres should be removed; since, by its combination with the colouring matter, it would be apt to form an external crust of mere pigment, which would block up the pores, obstruct the entrance of the dye into the interior, and also exhaust to no purpose the dyeing power of the bath. For this reason the stuffs, after the application of the mordant, are drained, squeezed, washed, and sometimes (particularly with cotton and linen, in calico printing), even hard dried in a hot stove.The saline mordants, moreover, should not in general possess the crystallizing property in any considerable degree, as this opposes their affinity of composition for the cloth. On this account the deliquescent acetates of iron and alumina are more ready to aid the dyeing of cotton than copperas and alum.Alum is the great mordant employed in wool dyeing. It is frequently dissolved in water, holding tartar equal to one fourth the weight of the alum in solution; by which addition its tendency to crystallize is diminished, and the resulting colour is brightened. The alum and tartar combine with the stuff without suffering any change, and are decomposed only by the action of the colouring matters in the dye bath. The alum operates solely in virtue of its sulphuric acid, and earthy basis; the sulphate of potash present in that salt being rather injurious. Hence, if a sulphate of alumina free from iron could be readily obtained, it would prove a preferable mordant to alum. It is also probable, for the reason above assigned, that soda alum, a salt much less apt to crystallize than potash or ammonia alum, would suit the dyer very well. In order to counteract the tendency of common alum to crystallize, and to promote its tendency to pass into a basic salt, one eighth part of its weight of potash is added to its solution, or the equivalent in chalk or soda.We shall conclude this account of the general principles of dyeing, with Mr. Delaval’s observations on the nature of dyes, and a list of the different substances used in dyeing, in reference to the colours produced by them.Sir Isaac Newton supposed coloured matters to reflect the rays of light; some bodies reflecting the more, others the less, refrangible rays most copiously; and this he conceived to be the true, and the only reason of their colours. Mr. Delaval, however, proved in the 2d vol. of the “Memoirs of the Philosophical and Literary Society of Manchester,” that, “in transparent coloured substances, the colouring substance does not reflect anylight; and that when, by intercepting the light which was transmitted, it is hindered from passing through substances, they do not vary from their former colour to any other colour, but become entirely black;” and he instances a considerable number of coloured liquors, none of them endued with reflective powers, which, when seen by transmitted light, appeared severally in their true colours; but all of them, when seen by incident light, appeared black; which is also the case of black cherries, black currants, black berries, &c., the juices of which appeared red when spread on a white ground, or otherwise viewed by transmitted instead of incident light; and he concludes, that bleached linen, &c. “when dyed or painted with vegetable colours, do not differ in their manner of acting on the rays of light, from natural vegetable bodies; both yielding their colours by transmitting through the transparent coloured matter, the light which is reflected from the white ground:” it being apparent, from different experiments, “that no reflecting power resides in any of their components, except in their white matter only,” and that “transparent coloured substances, placed in situations by which transmission of light through them is intercepted, exhibit no colour, but become entirely black.”The art of dyeing, therefore, (according to Mr. Delaval) “consists principally in covering white substances, from which light is strongly reflected, with transparent coloured media, which, according to their several colours, transmit more or less copiously the rays reflected from the white,” since “the transparent media themselves reflect no light; and it is evident that if they yielded their colours by reflecting, instead of transmitting the rays, the whiteness or colour of the ground on which they are applied, would not in anywise alter or affect the colours which they exhibit.”But when any opaque basis is interposed, the reflection is doubtless made by it, rather than by the substance of the dyed wool, silk, &c., and more especially when such basis consists of the white earth of alum, or the white oxide of tin; which, by their strong reflective powers, greatly augment the lustre of colours. There are, moreover, some opaque colouring matters, particularly the acetous, and other solutions of iron, used to stain linen, cotton, &c., which must necessarily themselves reflect, instead of transmitting the light by which their colours are made perceptible.The compound or mixed colours, are such as result from the combination of two differently coloured dye stuffs, or from dyeing stuffs with one colour, and then with another. The simple colours of the dyer, are red, yellow, blue, and black, with which, when skilfully blended, he can produce every variety of tint. Perhaps the dun or fawn colour might be added to the above, as it is directly obtained from a great many vegetable substances.1. Red with yellow, produces orange; a colour, which upon wool, is given usually with the spent scarlet bath. To this shade may be referred flame colour, pomegranate, capuchin, prawn, jonquil,cassis, chamois,café au lait, aurora, marigold, orange peel,mordorés, cinnamon, gold, &c. Snuff, chesnut, musk, and other shades are produced by substituting walnut peels or sumach for bright yellow. If a little blue be added to orange, an olive is obtained. The only direct orange dyes are annotto, and subchromate of lead; seeSilkandWoolDyeing.2. Red with blue produces purple, violet, lilac, pigeon’s neck, mallow, peach-blossom,bleu de roi, lint-blossom, amaranth.3. Red with black; brown, chocolate, marone, &c.4. Yellow with blue; green of a great variety of shades; such as nascent green, gay green, grass green, spring green, laurel green, sea green, celadon green, parrot green, cabbage green, apple green, duck green.5. Mixtures of colours, three and three, and four and four, produce an indefinite diversity of tints; thus red, yellow and blue, form brown olives, and greenish grays; in which the blue dye ought always to be first given, lest the indigo vat should be soiled by other colours. Red, yellow, and gray, (which is a gradation of black), give the dead-leaf tint, as well as dark orange, snuff colour, &c. Red, blue and gray give a vast variety of shades; as lead gray, slate gray, wood-pigeon gray, and other colours, too numerous to specify. SeeBrown Dye.The following list of dyes, and the colouring substances which produce them, may prove useful.Red.Cochineal,kermes,lac,madder,archil,carthamusorsafflower,brazil wood,logwood,periodide of mercury,alkanet.Yellow.Quercitron,weld,fustic(yellow wood),annotto, sawwort, dyer’s broom,turmeric,fustet(rhus cotinus),Persian and Avignon berries(rhamnus infectorius), willow, peroxide of iron;chromate of lead(chrome yellow),sulphuret of arsenic, hydrosulphuret of antimony;nitric acidon silk.Blue.Indigo,woad or pastel,Prussian blue,turnsole or litmus,logwoodwith a salt of copper.Black.Galls,sumach,logwood,walnut peels, and other vegetables which contain tannin and gallic acid, along with ferruginous mordants. The anacardium of India.Green.These are produced by the blue and yellow dyes skilfully combined; with the exception of thechrome green, and perhaps thecopper green of Schweinfurt.Orange.Annotto, and mixtures of red and yellow dyes; subchromate of lead.Brown.See the remarks at the beginning of this article;Brownin its alphabetical place;Calico Printing,Catechu, andManganese.Fawn, Dun or Root.Walnut peels,sumach, birch tree, henna,sandal wood. SeeCalico Printing, for a great variety of these dyes.Fig.364.and365.represent in a cross and longitudinal section the automatic dyeing steam copper, so generally employed in the well-appointed factories of Lancashire.Dyeing steam copperAis the long reel, composed at each end of six radial iron arms or spokes, bound at their outer extremities with a six-sided wooden frame; these two terminal hexagons are connected by long wooden laths, seen above and belowAinfig.365.Fshows the sloping border or ledge of the copper.BandCare rollers laid horizontally, for facilitating the continuous motion of the series of pieces of goods stitched together into an endless web, which are made to travel by the incessant rotations of the reel. Immediately above the rollerBinfig.364., all the spare foldings of the web are seen resting upon the sloping wooden grating, which guides them onwards in the direction indicated by the arrow. The dye stuffs are put within the middle grating, like a hen-coop, markedG. Each copper is 6 feet long, 31⁄2feet wide, 31⁄2feet deep, exclusive of the top ledge, 9 inches high. Such steam coppers are usually erected in pairs, and moved by a common horizontal bevel wheel seen atDinfig.365., fixed upon a vertical shaft, shifted into geer by a wheel at its top, with one of the driving shafts of the factory. Upon each side ofD, the two steam pipes for supplying the right and left hand coppers are seen; each provided with a stop cock for admitting, regulating, or cutting off the steam. These steam pipes descend atE E, the horizontal branch having several orifices in its upper surface. The horizontal shaft in a line with the axes of the reels, and which turns them, is furnished upon each side with a clutch for putting either of the reels into or out of geer, that is to say, setting it a going, or at rest, in a moment by the touch of a forked lever.The steam pipe of distributionElies horizontally near the bottom of the middle coop, as shown underGinfig.364., and sends up the steam through its numerous orifices, among the dye-stuffs and water by which it is covered. Thus the infusion or decoctionis continually advancing in the copper, during the incessant loco-motion of the endless web. The horizontal pipe traverses the copper from end to end, and is not stopped short in the middle. Each of these coppers can receive two, three or more parallel pieces of goods at a time, the reel and copper being divided into so many compartments by transverse wooden spars.
DYEING, (Teinture, Fr.;Färberei, Germ.) is the art of impregnating wool, silk, cotton, linen, hair, and skins, with colours not removable by washing, or the ordinary usage to which these fibrous bodies are exposed when worked up into articles of furniture or raiment. I shall here consider the general principles of the art, referring for the particular dyes, and peculiar treatment of the stuffs to be dyed, to the different tinctorial substances in their alphabetical places; such ascochineal,indigo,madder, &c.
Dyeing is altogether a chemical process, and requires for its due explanation and practice an acquaintance with the properties of the elementary bodies, and the laws which regulate their combinations. It is true that many operations of this, as of other chemical arts, have been practised from the most antient times, long before any just views were entertained of the nature of the changes that took place. Mankind, equally in the rudest and most refined state, have always sought to gratify the love of distinctionby staining their dress sometimes even their skin, with gaudy colours. Moses speaks of raiment dyed blue, and purple, and scarlet, and of sheep-skins dyed red; circumstances which indicate no small degree of tinctorial skill. He enjoins purple stuffs for the works of the tabernacle and the vestments of the high priest.
In the articleCalico Printing, I have shown from Pliny that the antient Egyptians cultivated that art with some degree of scientific precision, since they knew the use of mordants, or those substances which, though they may impart no colour themselves, yet enable white robes (candida vela) to absorb colouring drugs (colorem sorbendibus medicamentis). Tyre, however, was the nation of antiquity which made dyeing its chief occupation and the staple of its commerce. There is little doubt that purple, the sacred symbol of royal and sacerdotal dignity, was a colour discovered in that city, and that it contributed to its opulence and grandeur. Homer marks no less the value than the antiquity of this dye, by describing his heroes as arrayed in purple robes. Purple habits are mentioned among the presents made to Gideon by the Israelites from the spoils of the kings of Midian.
The juice employed for communicating this dye was obtained from two different kinds of shell-fish, described by Pliny under the names ofpurpuraandbuccinum; and was extracted from a small vessel, or sac, in their throats, to the amount of only one drop from each animal. A darker and inferior colour was also procured by crushing the whole substance of the buccinum. A certain quantity of the juice collected from a vast number of shells being treated with sea-salt, was allowed to ripen for three days; after which it was diluted with five times its bulk of water, kept at a moderate heat for six days more, occasionally skimmed to separate the animal membranes, and when thus clarified was applied directly as a dye to white wool, previously prepared for this purpose by the action of lime-water, or of a species of lichen called fucus. Two operations were requisite to communicate the finest Tyrian purple; the first consisted in plunging the wool into the juice of the purpura; the second, into that of the buccinum. Fifty drachms of wool required one hundred of the former liquor, and two hundred of the latter. Sometimes a preliminary tint was given with coccus, the kermes of the present day, and the cloth received merely a finish from the precious animal juice. The colours, though probably not nearly so brilliant as those producible by our cochineal, seem to have been very durable, for Plutarch says, in hisLife of Alexander, (chap. 36.), that the Greeks found in the treasury of the king of Persia a large quantity of purple cloth, which was as beautiful as at first, though it was 190 years old.[26]
[26]‘Among other things, there was purple of Hermione (?) to the amount of five thousand talents.’ (Plutarch’s Lives, translated by Langhorne, Wrangham’s edition, vol. v. p. 240.) Horace celebrates the Laconian dye in the following lines:—Nec Laconicas mihiTrahunt honestæ purpuras clientæ.(Carm., lib. ii., Ode 18.)
[26]‘Among other things, there was purple of Hermione (?) to the amount of five thousand talents.’ (Plutarch’s Lives, translated by Langhorne, Wrangham’s edition, vol. v. p. 240.) Horace celebrates the Laconian dye in the following lines:—
Nec Laconicas mihiTrahunt honestæ purpuras clientæ.(Carm., lib. ii., Ode 18.)
Nec Laconicas mihiTrahunt honestæ purpuras clientæ.(Carm., lib. ii., Ode 18.)
The difficulty of collecting the purple juice, and the tedious complication of the dyeing process, made the purple wool of Tyre so expensive at Rome that in the time of Augustus a pound of it cost nearly 30l.of our money.[27]Notwithstanding this enormous price, such was the wealth accumulated in that capital, that many of its leading citizens decorated themselves in purple attire, till the emperors arrogated to themselves the privilege of wearing purple, and prohibited its use to every other person. This prohibition operated so much to discourage this curious art as eventually to occasion its extinction, first in the western and then in the eastern empire, where, however, it existed in certain imperial manufactories till the eleventh century.
[27]Pliny says that a pound of the double-dipped Tyrian purple was sold in Rome for a hundred crowns.
[27]Pliny says that a pound of the double-dipped Tyrian purple was sold in Rome for a hundred crowns.
Dyeing was little cultivated in antient Greece; the people of Athens wore generally woollen dresses of the natural colour. But the Romans must have bestowed some pains upon this art. In the games of the circus parties were distinguished by colours. Four of these are described by Pliny, the green, the orange, the grey, and the white. The following ingredients were used by their dyers. A crude native alum mixed with copperas, copperas itself, blue vitriol, alkanet, lichen rocellus, or archil, broom, madder, woad, nut-galls, the seeds of pomegranate, and of an Egyptian acacia.
Gage, Cole, Plumier, Reaumur, and Duhamel have severally made researches concerning the colouring juices of shell-fish caught on various shores of the ocean, and have succeeded in forming a purple dye, but they found it much inferior to that furnished by other means. The juice of the buccinum is at first white; it becomes by exposure to air of a yellowish green bordering on blue; it afterwards reddens, and finally changes to a deep purple of considerable vivacity. These circumstances coincide with the minute description of the manner of catching the purple-dye shell-fish which we possess in the work of an eye-witness, Eudocia Macrembolitissa, daughter of the Emperor Constantine VIII., who lived in the eleventh century.
The moderns have obtained from the New World several dye-drugs unknown to the antients; such as cochineal, quercitron, Brazil wood, logwood, annatto; and they havediscovered the art of using indigo as a dye, which the Romans knew only as a pigment. But the vast superiority of our dyes over those of former times must be ascribed principally to the employment of pure alum and solution of tin as mordants, either alone or mixed with other bases; substances which give to our common dye-stuffs remarkable depth, durability, and lustre. Another improvement in dyeing of more recent date is the application to textile substances of metallic compounds, such as Prussian blue, chrome yellow, manganese brown, &c.
Indigo, the innoxious and beautiful product of an interesting tribe of tropical plants, which is adapted to form the most useful and substantial of all dyes, was actually denounced as a dangerous drug, and forbidden to be used, by our parliament in the reign of Queen Elizabeth. An act was passed authorizing searchers to burn both it and logwood in every dye-house where they could be found. This act remained in full force till the time of Charles II.; that is, for a great part of a century. A foreigner might have supposed that the legislators of England entertained such an affection for their native woad, with which their naked sires used to dye their skins in the old times, that they would allow no outlandish drug to come in competition with it. A most instructive book might be written illustrative of the evils inflicted upon arts, manufactures, and commerce, in consequence of the ignorance of the legislature.[28]
[28]Author, in Penny Cyclopedia.
[28]Author, in Penny Cyclopedia.
Colours are not, properly speaking, material; they are impressions which we receive from the rays of light reflected, in a decomposed state, by the surfaces of bodies. It is well known that a white sunbeam consists of an indeterminate number of differently coloured rays, which being separated by the refractive force of a glass prism, form the solar spectrum, an image distinguishable into seven sorts of rays; the red, orange, yellow, green, blue, indigo, and violet. Hence, when an opaque body appears coloured, for example, red, we say that it reflects the red rays only, or in greatest abundance, mixed with more or less of the white beam, which has escaped decomposition. According to this manner of viewing the colouring principle, the art of dyeing consists in fixing upon stuffs, by means of corpuscular attraction, substances which act upon light in a different manner from the surfaces of the stuffs themselves. The dyer ought, therefore, to be familiar with two principles of optics; the first relative to the mixture of colours, and the second to their simultaneous contrast.
Whenever the different coloured rays, which have been separated by the prism, are totally reunited, they reproduce white light. It is evident, that in this composition of light, if some rays were left out, or if the coloured rays be not in a certain proportion, we should not have white light, but light of a certain colour. For example; if we separate the red rays from the light decomposed by a prism, the remaining coloured rays will form by their combination a peculiar bluish green. If we separate in like manner the orange rays, the remaining coloured rays will form by their combination a blue colour. If we separate from the decomposed prismatic light the rays of greenish yellow, the remaining coloured rays will form a violet. And if we separate the rays of yellow bordering on orange, the remaining coloured rays will form by their union an indigo colour.
Thus we see that every coloured light has such a relation with another coloured light that, by uniting the first with the second, we reproduce white light; a relation which we express by saying that the one is the complement of the other. In this sense, red is the complementary colour of bluish green; orange, of blue; greenish yellow, of violet; and orange yellow, of indigo. If we mix the yellow ray with the red, we produce orange; the blue ray with the yellow, we produce green; and the blue with the red, we produce violet or indigo, according as there is more or less red relatively to the blue. But these tints are distinguishable from the orange, green, indigo, and violet of the solar spectrum, because when viewed through the prism they are reduced to their elementary component colours.
If the dyer tries to realize the preceding results by the mixture of dyes, he will succeed only with a certain number of them. Thus, with red and yellow he can make orange; with blue and yellow, green; with blue and red, indigo or violet. These facts, the results of practice, have led him to conclude that there are only three primitive colours; the red, yellow, and blue. If he attempts to make a white, by applying red, yellow, and blue dyes in certain quantities to a white stuff, in imitation of the philosopher’s experiment on the synthesis of the sunbeam, far from succeeding, he will deviate still further from his purpose, since the stuff will by these dyes become so dark coloured, as to appear black.
This fact must not, however, lead us to suppose that in every case where red, yellow, and blue are applied to white cloth, black is produced. In reality, when a little ultramarine, cobalt blue, Prussian blue, or indigo, is applied to goods with the view of giving them the best possible white, if only a certain proportion be used, the goods will appear whiter after this addition than before it. What happens in this case? The violet blueforms, with the brown yellow of the goods, a mixture tending to white, or less coloured than the yellow of the goods and the blue together were. For the same reason, a mixture of prussian blue and cochineal pink has been of late years used in the whitening or the azuring of silks, in preference to a pure blue; for on examining closely the colour of the silk to be neutralized, it was found by the relations of the complementary colours, that the violet was more suitable than the indigo blue formerly used. The dyer should know, that when he applies several different colouring matters to stuffs, as yellow and blue, for example, if they appear green, it is because the eye cannot distinguish the points which reflect the yellow from those which reflect the blue; and that, consequently, it is only where the distinction is not possible, that a mixture or combination appears. When we examine certain gray substances, such as hairs, feathers, &c., with the microscope, we see that the gray colour results from black points, disseminated over a colourless or slightly coloured surface. In reference to compound colours, this instrument might be used with advantage by the dyer.
The dyer should be acquainted also with the law of the simultaneous contrast of colours. When the eye views two colours close alongside of each other, it sees them differing most in their optical composition, and in the height of their tone, when the two are not equally pale or full-bodied. They appear most different as to their optical composition, when the complementary of the one of them is added to the colour of the other. Thus, put a green zone alongside of an orange zone; the red colour complementary of green, being added to the orange, will make it appear redder; and in like manner the blue, complementary of orange, being added to the green, will make it appear more intensely blue. In order to appreciate these differences, let us take two green stripes and two orange stripes, placing one of the green stripes near one of the orange; then place the two others so that the green stripe may be at a distance from the other green stripe, but on the same side, and the orange at a distance from the other orange, also on the same side.
As to the contrast in the height of the tone, we may satisfy ourselves by taking the tones No. 1. No. 2. No. 15. and No. 16. from a graduated pallet of reds: for example, by placing No. 2. and No. 15. close alongside, putting No. 1. at a distance from No. 2. on the same side, and No. 16. at a distance from No. 15. on the same side,—we shall see (if the pallet is sufficiently lowered in tone) No. 2. equal to No. 1., and No. 15. equal to No. 16.; whence it follows that No. 2., by the vicinity of No. 15., will appear to have lost some of its colour; while No. 15. will appear to have acquired colour. When black or gray figures are printed upon coloured grounds, these figures are of the colour complementary of the ground. Consequently, in order to judge of their colour, we must cut out spaces in a piece of gray or white paper, so as to allow the eye to see nothing but the figures; and if we wish to compare figures of the same colour, applied upon grounds of different colours, we can judge rightly of the figures only by insulating them from the grounds.
The relations of dyeing with the principles of chemistry, constitute the theory of the art, properly speaking; this theory has for its basis, the knowledge—1. of the species of bodies which dyeing processes bring into contact; 2. of the circumstances in which these species act; 3. of the phenomena which appear during their action; and 4. of the properties of the coloured combinations which are produced. These generalities may be specified under the ten following heads:—
1. The preparation of the stuffs to be dyed, whether fibres, yarn, or cloth; under the heads of ligneous matter, cotton, hemp, flax; and of the animal matters, silk and wool.
2. The mutual action of these stuffs, and simple bodies.
3. The mutual action of these stuffs, and acids.
4. The mutual action of these stuffs, and salifiable bases, as alumina, &c.
5. The mutual action of these stuffs, and salts.
6. The mutual action of these stuffs, and neutral compounds not saline.
7. The mutual action of these stuffs, and of one or more definite compounds.
8. Of dyed stuffs considered in reference to the fastness of their colour, under the influence of heat, light, water, oxygen, air, boilings with soap, and reagents.
9. Of dyeing, considered in its connections with chemistry.
10. Of dyeing, considered in its relations with caloric, mechanics, hydraulics, and optics.
1. The preparation of stuffs.
The operations to which stuffs are subjected before dyeing, are intended—1. to separate from them any foreign matters; 2. to render them more apt to unite with the colouring tinctures which the dyer proposes to fix upon them, in order to give them a more agreeable, or more brilliant aspect, or to lessen their tendency to assume a soiled appearance by use, which white surfaces so readily do. The foreign matters are either naturally inherent in the stuffs, or added to them in the spinning, weaving, or othermanipulation of manufacture. The ligneous fibres must be freed from the coloured azotized varnish on their surface, from a yellow colouring matter in their substance, from some lime and iron, from chlorophylle or leaf-green, and from pectic acid; all natural combinations. Some of these principles require to be oxygenized, before alkaline lyes can cleanse them, as I have stated in the articleBleaching, which may be consulted in reference to this subject. See alsoSilkandWool. A weak bath of soda has the property of preparing wool for taking on a uniform dye, but it must be well rinsed and aired before being put into the dye-vat.
2. Mutual action of stuffs, and simple bodies.
Stuffs chemically considered being composed of three or four elements, already in a state of reciprocal saturation, have but a feeble attraction for simple substances. We know in fact, that the latter combine only with each other, or with binary compounds, and that in the greater number of cases where they exert an action upon more complete compounds, it is by disturbing the arrangement of their elements, and not by a resulting affinity with the whole together.
3, 4. Although stuffs may in a general point of view be considered as neutral in relation to colouring reagents, yet experience shows that they are more disposed to combine with acid than with alkaline compounds; and that consequently their nature seems to be more alkaline than acid. By steeping dry wool or other stuff in a clean state in an alkaline or acid solution of known strength, and by testing the liquor after the stuff is taken out, we shall ascertain whether there be any real affinity between them, by the solution being rendered more dilute in consequence of the abstraction of alkaline or acid particles from it. Wool and silk thus immersed, abstract a portion of both sulphuric and muriatic acids; but cotton and flax imbibe the water, with the rejection of a portion of the acid. The acid may be again taken from the stuffs by washing them with a sufficient quantity of water.
5. The affinity between saline bodies and stuffs may be ascertained in the same way as that of acids, by plunging the dry stuffs into solutions of the salts, and determining the density of the solution before the immersion, and after withdrawing the stuffs. Wool abstracts alum from its solution, but it gives it all out again to boiling water. The sulphates of protoxide of iron, of copper and zinc resemble alum in this respect. When silk is steeped for some time in solution of protosulphate of iron, it abstracts the oxide, gets thereby dyed, and leaves the solution acidulous. Wool put in contact with cream of tartar decomposes a portion of it; it absorbs the acid into its pores, and leaves a neutral salt in the liquor. The study of the action of salts upon stuffs is at the present day the foundation of the theory of dyeing; and some of them are employed immediately as dye-drugs.
6. Mutual action of stuffs, and neutral compounds not saline.
Several sulphurets, such as those of arsenic, lead, copper, antimony, tin, are susceptible of being applied to stuffs, and of dyeing them in a more or less fast manner. Indigo, hematine, breziline, carmine, and the peculiar colouring principles of many dyes belong to this division.
7. Mutual action of goods with one or more definite compounds, and dye-stuffs.
I shall consider here in a theoretical point of view, the most general results which a certain number of organic colouring matters present, when applied upon stuffs by the dyer.
Indigo.This dye-drug, when tolerably good, contains half its weight of indigotine. The cold vat is prepared commonly with water, copperas, indigo, lime, or sometimes carbonate of soda, and is used almost exclusively for cotton and linen; immersion in acidulated water is occasionally had recourse to for removing a little oxide of iron which attaches itself to the cloth dyed in this vat.
The indigo vat for wool and silk is mounted exclusively with indigo, good potashes of commerce, madder and bran. In this vat, the immediate principles with base of carbon and hydrogen, such as the extracts of madder and bran, perform the disoxidizing function of the copperas in the cold vat. The pastel vats require most skill and experience, in consequence of their complexity. The greatest difficulty occurs in keeping them in a good condition, because they vary progressively as the dyeing goes on, by the abstraction of the indigotine, and the modification of the fermentable matter employed to disoxygenate the indigo. The alkaline matter also changes by the action of the air. By the successive additions of indigo, alkali, &c., this vat becomes very difficult to manage with profit and success. The great affair of the dyer is the proper addition of lime; too much or too little being equally injurious.
Sulphate of indigo or Saxon blue is used also to dye silk and wool. If the wools be ill sorted it will show their differences by the inequalities of the dye. Wool dyed in this bath put into water saturated with sulphuretted hydrogen, becomes soon colourless, owing to the disoxygenation of the indigo. The woollen cloth when exposed to the air for some time, resumes its blue colour, but not so intensely as before.
The properties of hematine explain the mode of using logwood. When stuffs are dyed in the infusion or decoction of this wood, under the influence of a base which acts upon the hematine in the manner of an alkali, a blue dye bordering upon violet is obtained. Such is the process for dyeing cotton and wool a logwood blue by means of verdigris, crystallized acetate of copper, and acetate of alumina.
When we dye a stuff yellow, red, or orange, we have always bright tints; with blue we may have a very dark shade, but somewhat violet; the proper black can be obtained only by using the three colours, blue, red, and yellow, in proper proportions. Hence we can explain how the tints of yellow, red, orange, blue, green, and violet, may be browned, by applying to them one or two colours which along with themselves would produce black; and also we may explain the nature of that variety of blacks and grays which seems to be indefinite. Nutgalls and sulphate of iron, so frequently employed for the black dye, give only a violet or bluish gray. The pyrolignite of iron, which contains a brown empyreumatic matter, gives to stuffs a brown tint, bordering upon greenish yellow in the pale hues, and to chestnut brown in the dark ones. By galling cotton and silk, and giving them a bath of pyrolignite of iron, we may after some alternations dye them black. Galls, logwood, and a salt of iron, produce merely a very deep violet blue; but by boiling and exposure to air, the hematate of iron is changed, becoming red-brown, and favours the production of black. Galls and salts of copper dye stuffs an olive drab, logwood and salts of copper a violet blue; hence their combination should produce a black. In using sumach as a substitute for galls, we should take into account the proportion of yellow matter it contains. When the best possible black is wanted upon wool, we must give the stuff a foundation of indigo, then pass it into a bath of logwood, sumach, and proto-sulphate of iron. The sumach may be replaced by one third of its weight of nutgalls.
8. Of dyed stuffs considered in reference to the fastness of their colours, when exposed to water, light, heat, air, oxygen, boiling and reagents.
Pure water without air has no action upon any properly dyed stuff.
Heat favours the action of certain oxygenized bodies upon the carbonaceous and hydrogenous constituents of the stuff; as is seen with regard to chromic acid, and peroxide of manganese upon cotton goods. It promotes the solvent action of water, and it even affects some colours. Thus Prussian blue applied to silk, is reduced to peroxide of iron by long boiling.
Light without contact of air affects very few dyes.
Oxygen, especially in the nascent state, is very powerful upon dyes. SeeBleaching.
The atmosphere in a somewhat moist state affects many dyes, at an elevated temperature. Silk dyed pink, with safflower, when heated to 400° F. becomes of a dirty white hue in the course of an hour. The violet of logwood upon alumed wool becomes of a dull brown at the same temperature in the same time. But both stand a heat of 300° F. Brazil red dye, turmeric, and weld yellow dyes display the same phenomena. These facts shew the great fixity of colours commonly deemed tender. The stuffs become affected to a certain degree, under the same circumstances as the dyes. The alterability even of indigo in the air is shewn in the wearing of pale blue clothes; in the dark blue cloth there is such a body of colour, that it resists proportionally longer; but the seams of coats exhibit the effect very distinctly. In silk window curtains, which have been long exposed to the air and light, the stuff is found to be decomposed as well as the colour.
Boilingwas formerly prescribed in France as a test of fast dyes. It consisted in putting a sample of the dyed goods in boiling water, holding in solution a determinate quantity of alum, tartar, soap, and vinegar, &c. Dufay improved that barbarous test. He considered that fast-dyed cloth could be recognized by resisting an exposure of twelve hours to the sunshine of summer, and to the midnight dews; or of sixteen days in winter.
In trying the stability of dyes, we may offer the following rules:—
That every stuff should be exposed to the light and air; if it be intended to be worn abroad, it should be exposed also to the wind and rain; that carpets moreover should be subjected to friction and pulling, to prove their tenacity; and that cloths to be washed should be exposed to the action of hot water and soap.
In examining a piece of dyed cotton goods, we may proceed as follows:—
Suppose its colour to be orange-brown. We find first that it imparts no colour to boiling water; that protochloride of tin takes out its colour; that plunged into a solution of ferroprussiate of potash it becomes blue; and that a piece of it being burned, leaves a residuum of peroxide of iron; we may thence conclude that the dyeing matter is peroxide of iron.
Suppose we have a blue stuff which may have been dyed either with indigo or with Prussian blue, and we wish to know what it will become in use. We inquire first into the nature of the blue. Hot water slightly alkaline will be coloured blue by it, ifit has been dyed with sulphate of indigo; it will not be coloured if it was dyed in the indigo vat, but it will become yellow by nitric acid. Boiling water, without becoming coloured itself, will destroy the Prussian blue dye; an alkaline water will convert its colour into an iron rust tint; nitric acid, which makes the indigo dye yellow, makes that of Prussian blue green. The liquor resulting from boiling alkaline water on the Prussian blue cloth, will convert sulphate of iron into Prussian blue.
9. Division. Of dyeing viewed in its relation to chemistry.
The phenomena of dyeing have been ascribed to very different causes; by some they were supposed to depend upon mechanical causes, and by others upon the forces from which chemical effects flow. Hellot, in conformity with the first mode of explanation, thought that the art of dyeing consisted essentially in opening the pores in order to admit colouring matters into them, and to fix them there by cooling, or by means of a mordant imagined to act like a cement.
Dufay in 1737, Bergmann in 1776, Macquer in 1778, and Berthollet in 1790, had recourse to chemical affinities, to explain the fixation of the colouring principles upon stuffs, either without an intermedium, like indigo, walnut peels, annotto; or by the intervention of an acid, a salifiable base, or a salt, which were called mordants. When bodies present phenomena which we refer to an attraction uniting particles of the same nature, whether simple or compound, to form an aggregate, or to an affinity which unites the particles of different natures to form them into a chemical compound, these bodies are in apparent contact. This happens precisely in all the cases of the mutual action of bodies in an operation of dyeing; if their particles were not in apparent contact, there would be absolutely no change in their respective condition. When we see stuffs and metallic oxides in apparent contact, form a mutual union of greater or less force, we cannot therefore help referring it to affinity. We do not know how many dyes may be fixed upon the same piece of cloth; but in the operations of the dye-house sufficiently complex compounds are formed, since they are always stuffs, composed of three or four elements, which are combined with at least binary acid or basic compounds; with simple salts compounded themselves of two immediate principles at least binary; with double salts composed of two simple salts; and finally with organic dye-stuffs containing three or four elements. We may add that different species belonging to one of these classes, and different species belonging to different classes, may unite simultaneously with one stuff. The union of stuffs with colouring matters appears, in general, not to take place in definite proportions; though there are probably some exceptions.
We may conclude this head by remarking, that, besides the stuff and the colouring matter, it is not necessary, in dyeing, to distinguish a third body, under the name ofmordant; for the idea of mordant does not rest upon any definite fact; the body to which this name has been given being essentially only one of the immediate principles of the coloured combination which we wish to fix upon the stuff.
10. Division. Of dyeing in its relation with caloric, mechanics, hydraulics, pneumatics, and optics.
Dyeing baths, or coppers, are heated directly by a furnace, or by means of steam conducted in a pipe from a boiler at a certain distance from the bath. In the first case, the vessels are almost always made of copper; only, in special cases, for the scarlet and some delicate silk dyes, of tin; in the second case, they are of copper, iron, or wood. A direct fire is more economical than heating steam pipes, where there is only one or two baths to heat, or where the labours are often suspended. Madder and indigo vats, when heated by steam, have it either admitted directly into the liquor, or made to circulate through pipes plunged into it, or between the copper and an exterior iron or wood case. Seethe endof this article.
Every thing else being equal, dyeing with heat presents fewer difficulties towards obtaining an evenly colour, than dyeing in the cold; the reason of which may be found in the following facts:—The air adhering to the surface of stuffs, and that interposed between the fibres of their constituent yarns, is more easily extricated in a hot bath than a cold one, and thus allows the dye liquor to penetrate more easily into their interior: in the second place, the currents which take place in a hot bath, and which tend incessantly to render its contents uniform, by renewing continually the strata of liquid in contact with the stuff, contribute mainly to render the dyeing evenly. In cold dyeing, it is necessary to stir up the bath from time to time; and when goods are first put in, they must be carefully dipped, then taken out, pressed, and wrung, several times in succession till they be uniformly moistened.
The mechanical relations are to be found in the apparatus employed for wincing, siring, and pressing the goods, as we have described underCalico PrintingandBandanna. The hydraulic relations refer to the wash-wheels and other similar apparatus, of which an account is given under the same articles. The optical relationshave been already considered. In the sequel of this article an automatic dyeing vat will be described.
The extracts of solutions of native dye-stuffs may be divided into two classes, in reference to their habitudes with the oxygen of the atmosphere; such as continue essentially unaltered in the air, and such as suffer oxidation, and thereby precipitate a determinate colouring matter. The dyes contained in the watery infusions of the different vegetable and animal substances which do not belong to the second class, are feebly attached to their solvents, and quit them readily for any other bodies that possess an attraction for them. On this principle, a decoction of cochineal, logwood, brazil wood, or a solution of sulphate of indigo, by digestion with powdered bone black, lose their colour, in consequence of the colouring particles combining by a kind of capillary attraction with the porous carbon, without undergoing any change. The same thing happens when well-scoured wool is steeped in such coloured liquids; and the colours which the wool assumes by its attraction for the dye, is, with regard to most of the above coloured solutions, but feeble and fugitive, since the dye may be again abstracted by copious washing with simple water, whose attractive force therefore overcomes that of the wool. The aid of a high temperature, indeed, is requisite for the abstraction of the colour from the wool and the bone-black, probably by enlarging the size of the pores, and increasing the solvent power of the water.
Those dye-baths, on the contrary, whose colouring matter is of the nature of extractive or apothème, form a faster combination with stuffs. Thus the yellow, fawn, and brown dyes, which contain tannin and extractive, become oxygenated by contact of air, and insoluble in water; by which means they can impart a durable dye. When wool is impregnated with decoctions of that kind, its pores get charged by capillarity, and when the liquid becomes oxygenated, they remain filled with a colour now become insoluble in water. A similar change to insolubility ensues when the yellow liquor of the indigo vat gets oxidized in the pores of cotton and wool, into which it had been introduced in a fluid state. The same change occurs when protosulphate of iron is converted into persulphate, with the deposition of an insoluble peroxide in the substance of the stuff. The change here effected by oxidation can, in other circumstances, be produced by acids which have the power of precipitating the dye-stuff in an insoluble state, as happens with decoction of fustic.
Hence we perceive that the dyeing of fast colours rests upon the principle, that the colours dissolved in the vat, during their union with the stuff, should suffer such a change as to become insoluble in their former menstruum. The more this dye, as altered in its union with the stuff, can resist other menstrua or agents, the faster it will be. This is the essential difference between dyeing and painting; or applying a coat of pigment devoid of any true affinity for the surface.
If we mix a clear infusion of a dye with a small quantity of a solution of an earthy or metallic salt, both in water, the limpid liquids soon become turbid, and there gradually subsides sooner or later, according to the nature of the mixture, a coloured precipitate, consisting of the altered dye united with a basic or subsalt. In this compound the colouring matter seems to act the part of an acid, which is saturated by a small quantity of the basis, or in its acid relationship is feeble, so that it can also combine with acids, being in reference to them a base. The decomposition of a salt, as alum, by dyes, is effected principally through the formation of an insoluble subsalt, with which the colour combines, while a supersalt remains in the bath, and modifies, by its solvent reaction, the shade of the dyed stuff. Dyed stuffs may be considered as composed of the fibrous body intimately associated with the colouring matter, the oxide, and acid, all three constituting a compound salt. Many persons have erroneously imagined, that dyed goods contained none of the acid employed in the dye bath; but they forget that even potash added to alum does not throw down the pure earthy basis, but a subsalt; and they should not ascribe to colouring matter a power of decomposition at all approaching to that of an alkali. Salts, containing strong acids, saturate a very large quantity of colouring matter, in proportion to their place in the scale of chemical equivalents. Mere bases, such as pure alumina, and pure oxide of tin, have no power of precipitating colouring matter; when they seem to do so, they always contain some acid.
Such salts, therefore, as have a tendency to pass readily into the basic state, are peculiarly adapted to act as mordants in dyeing, and to form coloured lakes. Magnesia affords as fine a white powder as alumina, and answers equally well to dilute lakes, but its soluble salts cannot be employed to form lakes, because they do not pass into the basic state. This illustration is calculated to throw much light upon dyeing processes in general.
The colour of the lake depends very much upon the nature of the acid, and the basis of the precipitating salt. If it be white, like alumina and oxide of tin, the lake will have, more or less, the colour of the dye, but brightened by the reflection of whitelight from the basis; while the difference of the acid occasions a difference in the hue. The coloured bases impart more or less of their colour to the lakes, not merely in virtue of their own tints, but of their chemical action upon the dye.
Upon these principles a crimson precipitate is obtained from infusions of cochineal by alum and salt of tin, which becomes scarlet by the addition of tartar; by acetate of lead, a violet blue precipitate is obtained, which is durable in the air; by muriate of lime, a pink brown precipitate falls, which soon becomes black, and at last dirty green; by the solution of a ferruginous salt, the precipitates are dark violet, and black; and, in like manner, all other salts with earthy or metallic bases, afford diversities of shade with cochineal. If this dye stuff be dissolved in weak water of ammonia, and be precipitated with acetate of lead, a green lake is obtained, which, after some time, will become green on the surface by contact of air, but violet and blue beneath. Hence it appears, that the shade of colour of a lake depends upon the degree of oxidation or change of the colour caused by the acid of the precipitating salt, upon the degree of oxidation or colour of the oxide which enters into union with the dye, and upon its quantity in reference to that of the colouring principle.
Such lakes are the difficultly soluble salts which constitute the dyeing materials of stuffs. Their particles, however, for the purposes of dyeing, must exist in a state of extremely fine division in the bath liquor, in order that they may penetrate along with it into the minute pores of textile fibres, and fill the cavities observed by means of the microscope in the filaments of wool, silk, cotton, and flax. I have examined these stuffs with an achromatic microscope, and find that when they are properly dyed with fast colours, the interior of their tubular texture is filled, or lined at least, with colouring matter. When the bath contains the colouring particles, so finely divided that they can pass through filtering paper, it is capable of dyeing; but if the infusion mixed with its mordant be flocculent and ready to subside, it is unfit for the purpose. In the latter case, the ingredients of the dye have already become aggregated into compounds too coherent and too gross for entering into combination with fibrous stuffs. Extractive matter and tannin are particularly liable to a change of this kind, by the prolonged action of heat in the bath. Hence also an alkaline solution of a colouring matter, affords no useful dye bath, when mixed with the solution of a salt having an earthy or metallic basis.
These circumstances, which are of frequent occurrence in the dye-house, render it necessary always to have the laky matter in a somewhat soluble condition, and to effect its precipitation within the pores of the stuffs, by previously impregnating them with the saline solutions by the aid of heat, which facilitates their introduction.
When a mordant is applied to any stuff, the portion of it remaining upon the surface of the fibres should be removed; since, by its combination with the colouring matter, it would be apt to form an external crust of mere pigment, which would block up the pores, obstruct the entrance of the dye into the interior, and also exhaust to no purpose the dyeing power of the bath. For this reason the stuffs, after the application of the mordant, are drained, squeezed, washed, and sometimes (particularly with cotton and linen, in calico printing), even hard dried in a hot stove.
The saline mordants, moreover, should not in general possess the crystallizing property in any considerable degree, as this opposes their affinity of composition for the cloth. On this account the deliquescent acetates of iron and alumina are more ready to aid the dyeing of cotton than copperas and alum.
Alum is the great mordant employed in wool dyeing. It is frequently dissolved in water, holding tartar equal to one fourth the weight of the alum in solution; by which addition its tendency to crystallize is diminished, and the resulting colour is brightened. The alum and tartar combine with the stuff without suffering any change, and are decomposed only by the action of the colouring matters in the dye bath. The alum operates solely in virtue of its sulphuric acid, and earthy basis; the sulphate of potash present in that salt being rather injurious. Hence, if a sulphate of alumina free from iron could be readily obtained, it would prove a preferable mordant to alum. It is also probable, for the reason above assigned, that soda alum, a salt much less apt to crystallize than potash or ammonia alum, would suit the dyer very well. In order to counteract the tendency of common alum to crystallize, and to promote its tendency to pass into a basic salt, one eighth part of its weight of potash is added to its solution, or the equivalent in chalk or soda.
We shall conclude this account of the general principles of dyeing, with Mr. Delaval’s observations on the nature of dyes, and a list of the different substances used in dyeing, in reference to the colours produced by them.
Sir Isaac Newton supposed coloured matters to reflect the rays of light; some bodies reflecting the more, others the less, refrangible rays most copiously; and this he conceived to be the true, and the only reason of their colours. Mr. Delaval, however, proved in the 2d vol. of the “Memoirs of the Philosophical and Literary Society of Manchester,” that, “in transparent coloured substances, the colouring substance does not reflect anylight; and that when, by intercepting the light which was transmitted, it is hindered from passing through substances, they do not vary from their former colour to any other colour, but become entirely black;” and he instances a considerable number of coloured liquors, none of them endued with reflective powers, which, when seen by transmitted light, appeared severally in their true colours; but all of them, when seen by incident light, appeared black; which is also the case of black cherries, black currants, black berries, &c., the juices of which appeared red when spread on a white ground, or otherwise viewed by transmitted instead of incident light; and he concludes, that bleached linen, &c. “when dyed or painted with vegetable colours, do not differ in their manner of acting on the rays of light, from natural vegetable bodies; both yielding their colours by transmitting through the transparent coloured matter, the light which is reflected from the white ground:” it being apparent, from different experiments, “that no reflecting power resides in any of their components, except in their white matter only,” and that “transparent coloured substances, placed in situations by which transmission of light through them is intercepted, exhibit no colour, but become entirely black.”
The art of dyeing, therefore, (according to Mr. Delaval) “consists principally in covering white substances, from which light is strongly reflected, with transparent coloured media, which, according to their several colours, transmit more or less copiously the rays reflected from the white,” since “the transparent media themselves reflect no light; and it is evident that if they yielded their colours by reflecting, instead of transmitting the rays, the whiteness or colour of the ground on which they are applied, would not in anywise alter or affect the colours which they exhibit.”
But when any opaque basis is interposed, the reflection is doubtless made by it, rather than by the substance of the dyed wool, silk, &c., and more especially when such basis consists of the white earth of alum, or the white oxide of tin; which, by their strong reflective powers, greatly augment the lustre of colours. There are, moreover, some opaque colouring matters, particularly the acetous, and other solutions of iron, used to stain linen, cotton, &c., which must necessarily themselves reflect, instead of transmitting the light by which their colours are made perceptible.
The compound or mixed colours, are such as result from the combination of two differently coloured dye stuffs, or from dyeing stuffs with one colour, and then with another. The simple colours of the dyer, are red, yellow, blue, and black, with which, when skilfully blended, he can produce every variety of tint. Perhaps the dun or fawn colour might be added to the above, as it is directly obtained from a great many vegetable substances.
1. Red with yellow, produces orange; a colour, which upon wool, is given usually with the spent scarlet bath. To this shade may be referred flame colour, pomegranate, capuchin, prawn, jonquil,cassis, chamois,café au lait, aurora, marigold, orange peel,mordorés, cinnamon, gold, &c. Snuff, chesnut, musk, and other shades are produced by substituting walnut peels or sumach for bright yellow. If a little blue be added to orange, an olive is obtained. The only direct orange dyes are annotto, and subchromate of lead; seeSilkandWoolDyeing.
2. Red with blue produces purple, violet, lilac, pigeon’s neck, mallow, peach-blossom,bleu de roi, lint-blossom, amaranth.
3. Red with black; brown, chocolate, marone, &c.
4. Yellow with blue; green of a great variety of shades; such as nascent green, gay green, grass green, spring green, laurel green, sea green, celadon green, parrot green, cabbage green, apple green, duck green.
5. Mixtures of colours, three and three, and four and four, produce an indefinite diversity of tints; thus red, yellow and blue, form brown olives, and greenish grays; in which the blue dye ought always to be first given, lest the indigo vat should be soiled by other colours. Red, yellow, and gray, (which is a gradation of black), give the dead-leaf tint, as well as dark orange, snuff colour, &c. Red, blue and gray give a vast variety of shades; as lead gray, slate gray, wood-pigeon gray, and other colours, too numerous to specify. SeeBrown Dye.
The following list of dyes, and the colouring substances which produce them, may prove useful.
Red.Cochineal,kermes,lac,madder,archil,carthamusorsafflower,brazil wood,logwood,periodide of mercury,alkanet.
Yellow.Quercitron,weld,fustic(yellow wood),annotto, sawwort, dyer’s broom,turmeric,fustet(rhus cotinus),Persian and Avignon berries(rhamnus infectorius), willow, peroxide of iron;chromate of lead(chrome yellow),sulphuret of arsenic, hydrosulphuret of antimony;nitric acidon silk.
Blue.Indigo,woad or pastel,Prussian blue,turnsole or litmus,logwoodwith a salt of copper.
Black.Galls,sumach,logwood,walnut peels, and other vegetables which contain tannin and gallic acid, along with ferruginous mordants. The anacardium of India.
Green.These are produced by the blue and yellow dyes skilfully combined; with the exception of thechrome green, and perhaps thecopper green of Schweinfurt.
Orange.Annotto, and mixtures of red and yellow dyes; subchromate of lead.
Brown.See the remarks at the beginning of this article;Brownin its alphabetical place;Calico Printing,Catechu, andManganese.
Fawn, Dun or Root.Walnut peels,sumach, birch tree, henna,sandal wood. SeeCalico Printing, for a great variety of these dyes.
Fig.364.and365.represent in a cross and longitudinal section the automatic dyeing steam copper, so generally employed in the well-appointed factories of Lancashire.
Dyeing steam copper
Ais the long reel, composed at each end of six radial iron arms or spokes, bound at their outer extremities with a six-sided wooden frame; these two terminal hexagons are connected by long wooden laths, seen above and belowAinfig.365.Fshows the sloping border or ledge of the copper.BandCare rollers laid horizontally, for facilitating the continuous motion of the series of pieces of goods stitched together into an endless web, which are made to travel by the incessant rotations of the reel. Immediately above the rollerBinfig.364., all the spare foldings of the web are seen resting upon the sloping wooden grating, which guides them onwards in the direction indicated by the arrow. The dye stuffs are put within the middle grating, like a hen-coop, markedG. Each copper is 6 feet long, 31⁄2feet wide, 31⁄2feet deep, exclusive of the top ledge, 9 inches high. Such steam coppers are usually erected in pairs, and moved by a common horizontal bevel wheel seen atDinfig.365., fixed upon a vertical shaft, shifted into geer by a wheel at its top, with one of the driving shafts of the factory. Upon each side ofD, the two steam pipes for supplying the right and left hand coppers are seen; each provided with a stop cock for admitting, regulating, or cutting off the steam. These steam pipes descend atE E, the horizontal branch having several orifices in its upper surface. The horizontal shaft in a line with the axes of the reels, and which turns them, is furnished upon each side with a clutch for putting either of the reels into or out of geer, that is to say, setting it a going, or at rest, in a moment by the touch of a forked lever.
The steam pipe of distributionElies horizontally near the bottom of the middle coop, as shown underGinfig.364., and sends up the steam through its numerous orifices, among the dye-stuffs and water by which it is covered. Thus the infusion or decoctionis continually advancing in the copper, during the incessant loco-motion of the endless web. The horizontal pipe traverses the copper from end to end, and is not stopped short in the middle. Each of these coppers can receive two, three or more parallel pieces of goods at a time, the reel and copper being divided into so many compartments by transverse wooden spars.