Fig. 8Fig. 8. Tramping Machine or “Kicker.”(F. Blattner, Brooklyn, New York.)
Fig. 8. Tramping Machine or “Kicker.”
(F. Blattner, Brooklyn, New York.)
For tanning purposes, this property of absorbing oxygen is important, because only with drying oils can a true chamois tan be obtained, non-drying oils acting like mineraloils only as water-proofing materials. The details of the chamois process are not quite clear, there being considerable difference of opinion on the matter. But all the studies on the subject tend to prove that there are at least two phases to the process: first, the mechanical covering of the fibres with the fat, this property being common to all fats or oils which may be used; and second, the combination of the fat with the skin in some chemical way, as a result of the oxidation of the fat, a characteristic found only in the drying oils. During the oxidation of the fats, the glycerine in them is converted to acrolein or acryl-aldehyde, which also aids the tanning. It was at one time supposed that the tanning action was due to this aldehyde alone, but a chamois tan can be made with fatty substances from which all the glycerine has been removed. The evidence on this question, however, is not quite conclusive.
In general, the procedure of the chamois tan is as follows: The hydro-extracted, fleshed skins are rubbed on the flesh-side with a good quality of seal-oil. They are then folded up, and put into a ‘kicker,’ where they are tramped for two or three hours to work in the oil. The kicker is a machine such as shown inFig. 8consisting of a receptacle for the skins, and two wooden hammers which work up and down mechanically, turning and pounding the skins. (As many as 1000–1500 skins of the size of musk-rats can be worked at one time in such a machine.) The pelts are then taken out and hung up in a warm room for several hours, considerable oxidation taking place. Another coat of oil is then applied, which is again tramped in, and the skins are hung up once more and exposed to the air to cause the oil to oxidize. After the skins are sufficiently tanned they are rinsed in a weak soda solution to remove the excess oil, washed and dried. When skins with fine hair such as marten, sable, mink, etc., receive a chamois tan, they are not tramped in kickers as the delicate top-hair will be broken, and the value of the skin thereby reduced.Instead they are placed in small drums, together with metal balls of varying sizes and weights depending on theparticularfur treated, and the oil is worked in by rotating the drum. Such a ball-drum, as it is called, is shown inFig. 9.
Fig. 9Fig. 9. Ball Drum.(F. Blattner, Brooklyn, New York.)
Fig. 9. Ball Drum.
(F. Blattner, Brooklyn, New York.)
In conjunction with the chamois tan may be discussed the process of oiling, inasmuch as the method of application and the effect are both similar to the chamois tan up to a certain point. It is customary to treat skins tanned by any other method but the chamois process, with some oil in order to render them more impervious to water. The greatest variety of oils and fats can be used, the action in most cases being simply the mechanical isolation of the skin fibres by such a substance, thus corresponding to the firstor physical phase of the chamois tan. The chemical phase, if it takes place at all, is usually slight, and is merely incidental. Oiling is generally applied either before drying after tanning, or after drying, the oiled skins being placed in a kicker and tramped to cause the oil to penetrate. In some instances the oiling material is put in the same mixture as the tanning chemicals, and the tanning and oiling are effected simultaneously.
Among fatty substances used for oiling are mineral oils, such as paraffine oil, and vaseline; animal fats, like train oils, butter, egg-yolk, glycerine, neats-foot oil; vegetable oils, like olive oil, castor oil, cottonseed oil; also sulphonated castor oil and sulphonated neats-foot oil. These may be used singly or in various mixtures, an emulsion of an oil and a soft soap also being frequently employed.
Formaldehyde has proven to be of great value in the tanning of furs, usually in conjunction with other processes. Formaldehyde is a gas with a strong, irritating odor, and its 40% solution, which is the customary commercial form, also possesses this quality. When skins are treated for several hours with a very dilute solution of the commercial product, a leather is obtained which combines the properties of the alum tan and the chamois tan. Moreover, in the majority of observed cases, where furs have been tanned with formaldehyde, the skins seem to acquire a certain immunity to the attacks of vermin and moths. Although the skins do not in any way retain the odor of the formaldehyde, nevertheless these destructive agents seem to be repelled.
Numerous processes have been devised which use formaldehyde in connection with other substances for tanning. Thus in a German patent is described a method involving the alternate or simultaneous treatment of pelts with solutions of formaldehyde and alpha or beta naphthol.Both the formaldehyde and the naphthol exercise tanning actions, but the process is not used in practise.
In 1911, Stiasny, a well-known leather chemist produced a synthetic substance by the condensation of formaldehyde with a sulphonated phenol, forming an artificial tannin. This chemical, called “Neradol D,” exhibits many of the properties characteristic of true tannins, although in no way related by structure and composition. By the use of “Neradol D” a soft, white and flexible leather is obtained, and it is therefore a suitable tanning material for furs.
In many instances more than one method is employed in tanning the furs, and in this way what is known as a combination tan is produced. While the various individual processes described give more or less satisfactory results by themselves, they generally possess some features, which for certain purposes may be undesirable, and which can be eliminated or considerably reduced by using other processes at the same time or subsequently. Some of the combination methods are, pickle with chrome tan, alum tan with chrome tan, and formaldehyde tan with pickle, mineral tan or chamois tan. By means of such combinations various qualities of tanned furs can be obtained, and if it is desired to produce a pelt having certain special characteristics, this can be brought about by combining two or more standard methods.
Some illustrations of combined tannages are the following: Alum-chrome tan. The skins are tanned by the regular alum process, then the constituents of the chrome tan are dissolved directly in the same bath, and the chrome tan is effected as usual. Chrome-formaldehyde tan. To the regular chrome tan solution is added1⁄2lb. of formaldehyde for every 10 gallons of chrome liquor. The rest of the process is as ordinarily.
In practise, the vegetable tanning matters are not used for furs, although in some special instances gambier cutch may be employed occasionally with some other tan. However, many of these tannins also have dyeing properties, and are used in dyeing the furs. In this connection it must be mentioned that furs dyed with these materials also receive a vegetable tan, which improves the quality of the leather to a considerable extent.
In choosing a method for tanning any particular kind of fur, several factors must be considered. The nature of the pelt, insofar as it is weak or strong; the time, labor and cost of materials required by the tanning process; the effect on the leather of the different dyes and chemicals used in dyeing, if the skin is to be dyed, are a few of the points requiring attention and consideration.
For furs which are only to be dressed, a simple tan like the pickle will suffice in most cases. Special instances, such as the rabbit and mole already mentioned, and a few other furs are tanned by the alum method. The pickle is undoubtedly the cheapest and simplest method of tanning skins, and yields a soft, white leather which is permanent as long as it is kept dry. If it is put into water, about 25% of the salt contained within the pelt dissolves out, and the acid present swells up the tissues. If the skin is dried in this condition, it will come out hard and brittle, tending to crack very easily. By treating the leather before drying with a strong salt solution, a good deal of the extracted salt will be replaced, and on drying and stretching, it will work out soft. Skins tanned by the “Schrot-beize” are affected by water in quite the same manner as the pickled skins.
The alum tan gives a leather similar to that produced bythe pickle, but with the advantage that the skins possess greater stretch and flexibility. In its resistance to water, the alum-tanned pelt is quite as susceptible as the other. As a general rule, the skin absorbs about 6% of its weight of alum from the tanning solution, but gives up three-quarters of this when it is soaked in water, producing on drying, a hard, stiff leather. The chrome tan is especially impervious to water, easily resisting temperatures of 80° C., and even boiling water. It is employed to only a limited extent on account of the special effort and care required to obtain satisfactory results, also because the pelt acquires a pale blue-green color which is not desired on dressed skins. The chamois tan, and some of the combinations of the formaldehyde tan with the other methods, give very soft, flexible leathers which possess a sufficiently great resistance to the effects of water and heat.
In tests made to determine the best working temperatures for dyeing skins dressed by the salt-acid tan, and for skins dressed by the chamois process, some very interesting facts were brought out. These two tans were chosen because they represent opposite extremes, the salt-acid tan usually giving the poorest results, and the chamois tan giving the best results in practise in dyeing. Other methods, except the chrome, range between these two. The procedure in these experiments was to treat the skins at ordinary temperatures in water, or dilute solutions of the various chemicals and dyes usually employed in dyeing, and then heat these solutions until the leather just began to shrink and shrivel up. This point, called the shrinking point (S.P.), gave the temperature to which the skins could be subjected in the given solution without danger to the pelt. (The experiments and observations were made by Erich Schlottauer, while director of a large German fur dressing and dyeing plant).
The first observation made was that different furs tanned by the same process were affected differently in the samesolutions. Thus in plain water, three furs, all tanned by the acid-salt tan, had shrinking points varying by several degrees; similarly with two different furs tanned by the chamois process, there was a variation in the shrinking point of two degrees. The explanation of this discrepancy among the different skins may be that there was a slight difference in the conditions under which they were tanned, experiments showing that a maximum difference of 4° C. may exist among skins tanned by the same process, but not under the same or identical circumstances. Another reason for the variation may be the fact, that some skins are more greasy than others, and are thus more resistant to the effects of water or of some chemicals. The furs with the higher shrinking points in water were those which naturally are more greasy than the others.
Weak solutions of acids tend slightly to lower the shrinking point, while weak solutions of alkalies appreciably raise it, in both chamois-tanned and salt-acid-tanned skins. Solutions of dyes and mordants as a general rule increase the resistance of the skin to heat, varying quantities of these substances having no, or little different effects on the shrinking points. Previous treatment of the leather with some oil considerably raises the shrinking point of the pelt. Formaldehyde effects a great increase of the resistance of the skins to heat, especially with chamois-tanned furs. The experiments in this case were made by first treating the skins in the weak formaldehyde solution, and then determining the shrinking point in plain water.
Two skins, both dressed by the “Schrot-beize,” a Persian lamb and an astrachan, after dyeing had shrinking points almost 10degreeshigher than when undyed. The extra tannage which the skins received from the tannins used in the dye mixtures for these furs, accounts for this increased resistance to heat.
The following tables give the observed figures in the different experiments:
Table IAS.P.BS.P.CS.P.Salt-acid TanC.C.C.Australian Opossum46°58°45°Marmot45°50°42°Skunk47°56°43°Chamois TanMink52°61°45°Muskrat50°58°42°A—WaterB—Water plus 1% Ammonia (s.g. 0.910)C—Water plus 1% Sulphuric acid (66° Beaumé)
A—WaterB—Water plus 1% Ammonia (s.g. 0.910)C—Water plus 1% Sulphuric acid (66° Beaumé)
A—Water
B—Water plus 1% Ammonia (s.g. 0.910)
C—Water plus 1% Sulphuric acid (66° Beaumé)
Table IIAS.P.BS.P.CS.P.Salt-acid TanC.C.C.Australian Opossum53°52°54°Chamois TanMink59°59°59°A—1000 c.c. water plus 40 c.c. Peroxide plus 5 c.c. ammoniaB—500 c.c. water plus 2 grams Ursol D (Para-phenylene-diamine)C—500 c.c. water plus 5 grams Ursol D
A—1000 c.c. water plus 40 c.c. Peroxide plus 5 c.c. ammoniaB—500 c.c. water plus 2 grams Ursol D (Para-phenylene-diamine)C—500 c.c. water plus 5 grams Ursol D
A—1000 c.c. water plus 40 c.c. Peroxide plus 5 c.c. ammonia
B—500 c.c. water plus 2 grams Ursol D (Para-phenylene-diamine)
C—500 c.c. water plus 5 grams Ursol D
Table IIIAS.P.BS.P.CS.P.DS.P.Salt-acid TanC.C.C.C.Australian Opossum51°51°53°56°ChamoisMink59°59°61°62°A—500 c.c. water plus 5 grams ground nut-gallsB—300 c.c. water plus 2 grams pyrogallic acidC—500 c.c. water plus 2 grams potassium bichromateD—Water, after treating leather with rapeseed oil
A—500 c.c. water plus 5 grams ground nut-gallsB—300 c.c. water plus 2 grams pyrogallic acidC—500 c.c. water plus 2 grams potassium bichromateD—Water, after treating leather with rapeseed oil
A—500 c.c. water plus 5 grams ground nut-galls
B—300 c.c. water plus 2 grams pyrogallic acid
C—500 c.c. water plus 2 grams potassium bichromate
D—Water, after treating leather with rapeseed oil
Table IVAS.P.BS.P.CS.P.DS.P.Salt-acid TanC.C.C.C.Australian Opossum49°49°55°50°Chamois TanMink59°67°69°70°A—500 c.c. water plus 5 c.c. formaldehyde for 1 hourB—500 c.c. water plus 5 c.c. formaldehyde for 12 hoursC—500 c.c. water plus 10 c.c. formaldehyde for 3 hoursD—As in C, but treated with 500 c.c. water plus 5 c.c. ammonia, instead of water alone.
A—500 c.c. water plus 5 c.c. formaldehyde for 1 hourB—500 c.c. water plus 5 c.c. formaldehyde for 12 hoursC—500 c.c. water plus 10 c.c. formaldehyde for 3 hoursD—As in C, but treated with 500 c.c. water plus 5 c.c. ammonia, instead of water alone.
A—500 c.c. water plus 5 c.c. formaldehyde for 1 hour
B—500 c.c. water plus 5 c.c. formaldehyde for 12 hours
C—500 c.c. water plus 10 c.c. formaldehyde for 3 hours
D—As in C, but treated with 500 c.c. water plus 5 c.c. ammonia, instead of water alone.
Table VAS.P.BS.P.C.C.Persian Lamb44°54°Astrachan47°55°A—Before dyeingB—After dyeing
A—Before dyeingB—After dyeing
A—Before dyeing
B—After dyeing
As a result of these experiments it may be concluded that the maximum temperature for drying salt-acid tanned skins should be 40° C., while for chamois tanned skins the temperature may be permitted to reach 45° C. without any danger of the leather being affected. Moreover, in the case of pickled skins, the matter of extraction of the tanning agent, as well as that of the leather becoming “burned” may be effectively counteracted by brushing some oil or fat on to the leather side before dyeing the pelt.
The shrinking points of skins dressed by the various tanning methods are constant within certain limits, depending on the nature of the skin and on the conditions of tanning, and it is possible by observing the shrinking point, in conjunction with other characteristics of a given pelt, to determine what method of tanning was used.
One of the most important operations of all the fur dressing processes is the drying of the skins. For even when all the previous steps have been successfully completed, there is still a great possibility of the skin being injured if the drying is not properly and carefully carried out.
The essential requirements for good drying are proper temperature, uniformity and rapidity. The leather part of the fur cannot, in the moist state, resist temperatures exceeding about 45° centigrade, for when dried, the skin turns out hard and stiff, and cracks easily. The furs must therefore be dried at an initial temperature of 25° to 30° centigrade, and as the moisture is gradually removed, the temperature may be raised, for the less water that remains in the pelt, the less is the leather affected by the heat, and the more difficult is the removal of its aqueous content.
If the drying process is not a uniform one, that is, if all the skins in a lot are not subjected to the same drying conditions, then after the drying has proceeded for a certain time, some skins may be quite dry while others are not, or there may be as many different degrees of dryness as there are skins drying. There is also the possibility of great variation in the amount of moisture removed from different parts of the same skin. Such a state of affairs requires an extra expenditure of time, labor and heat power in order to get the whole lot of furs into a more or less uniform condition. Moreover in some kinds of furs, especiallythose with thick skins, when the drying is not even, there is danger of the epidermal layer drying away from the corium, and subsequently peeling and cracking. Uniformity of drying requires the maintenance of a reasonably constant temperature equally distributed throughout all parts of the space where the drying is done, so that all the furs may be dried under the same conditions.
Rapidity of drying is desirable not only because it is beneficial to the condition of the pelt, but also from the point of view of practical business economy. The space occupied by the drying should be as small as possible compatible with the volume of work, and with the efficiency of operation. Slow drying involves the use of much space to take care of all the skins to be dried, or an accumulation of pelts ready to be dried, neither of which conditions is efficient or desirable.
It was formerly the general custom, still practised in some establishments, to dry the skins by hanging them up, leather-side out on lines in a large room or loft, the heat being usually supplied by steam pipes. Such a procedure occupied often as long as two or three days to get complete drying, involved a great deal of labor, and the results were far from uniform. In fact, in order to get the skins more nearly equable, it was necessary to subject them to an additional operation. This usually consisted of rotating the skins in a closed drum for several hours, the constant intermingling of the pelts in contact with each other causing any moisture left in them to be evenly distributed throughout the whole lot. The skins, by this process also are rendered somewhat softer and more flexible, but by drying under proper conditions the entire extra operation can be dispensed with, the furs coming out quite as soft and flexible without the drumming.
A great improvement was the adoption of large fans to circulate the heated air in the loft, thereby approaching more nearly an even temperature. More modern deviceshave, however, been developed, whereby drying can be effected in the most uniform manner, with perfect control of temperature, and requiring the least possible consumption of space, time, labor and power. A typical arrangement consists of a large closed chamber, generally constructed of steel, and divided into several compartments each of which may be operated independently of the others. Air, heated over suitably located steam pipes to the required temperature, is forced through the various compartments by means of fans operated by power. The conditions may be varied in each compartment, as to temperature or humidity, both of which can easily be regulated, or all the compartments may be used together as one unit. The skins are hung up on rods or lines in the compartments, or on special frames for the purpose, which are then entered into the compartments and the doors shut. The dry, heated air is forced to pass over the skins, and takes up their moisture. At the further end of the drying chamber is another fan which removes the moisture-laden air after it has done its work. The drying is effected in from 6 to 24 hours, and all skins are obtained in the same condition, for the process is quite uniform and regular.
Within recent years there has been evolved a highly efficient and economical drying equipment, based on asomewhatdifferent principle than underlies any of the foregoing methods. The conveyor type of dryer, as it is called, is admirably suited to the needs of the fur dressing and dyeing industry, and is undoubtedly superior to any of the previous systems of drying furs, in that it affords an enormous saving of space, time, labor and power, and gives greater uniformity and presents better working conditions.
Fig. 10Fig. 10. Diagrammatic Views of Conveyor Dryer.a.Side View;b.End View.(Proctor & Schwartz, Inc., Philadelphia.)
Fig. 10. Diagrammatic Views of Conveyor Dryer.
a.Side View;b.End View.
(Proctor & Schwartz, Inc., Philadelphia.)
The conveyor dryer consists essentially of a steel enclosure, through which the skins pass on horizontal conveyors. Where special insulation is necessary, asbestos panels are used to line the enclosure, making the dryer absolutelyfireproof, and enabling the maximum utilization of heat. In the middle of the dryer are located the steam coils which furnish the heat, and in many instances exhaust steam can be used as the source of heat.Figure 10shows diagrammatically the arrangement and operation of the conveyor type of dryer. The enclosure is divided into several compartments,in each of which a different condition of temperature and humidity is maintained, the temperature being closely and accurately regulated by an automatic control, and once the dryer has been set for any condition, all skins will be dried exactly the same, regardless of weather or season.
Fig. 11Fig. 11. Conveyor Dryer.(Proctor & Schwartz, Inc., Philadelphia.)
Fig. 11. Conveyor Dryer.
(Proctor & Schwartz, Inc., Philadelphia.)
The skins to be dried are placed on poles which in turn are set on the horizontal conveyors as inFig. 11. As the skins pass through the compartments, large volumes of air, heated to the required temperature over the steam coils, are circulated among the skins by means of the fans. Exhaust fans, properly placed, remove a certain quantity of moisture-laden air when it has accomplished its full measure of work. When the skins on the conveyors have passed the full length of the dryer, they are entirely dry, and are then removed from the poles. (Fig. 12). The time required for drying varies according to the nature of the fur from 1–2 hours to 6–8 hours. In tests made to determine the relative efficiency of the conveyor type of dryer as against the old “loft” method, it was found that there was a saving of over 50% in power, and of 85% in floor space, as well as a great saving of labor, when the conveyor system was used, the number of skins dried in a given period of time being the same in both cases. The advantages of the new method are easily apparent, and the saving is sufficiently great with large lots of furs, to make an appreciable difference in the final cost of dressing.
If the skins have been dried by a modern drying system they all come out in a uniform condition, and are ready to go on immediately to the next operation. If, however, a form of the “loft” method of drying has been used, it is customary to subject the skins to an additional process. The dried pelts are put in drums with damp sawdust, and drummed for a short time in order to get them into the proper condition. The drumming is essential for the purpose of equalizing the condition of the pelts, some being drier than others, and as a consequence of the contact with the moist sawdust, they are all brought to the same degree of dryness. As a result of this operation also, the skins become considerably softened.
Fig. 12Fig. 12. Delivery End of Conveyor Dryer.(Proctor & Schwartz, Inc., Philadelphia.)
Fig. 12. Delivery End of Conveyor Dryer.
(Proctor & Schwartz, Inc., Philadelphia.)
Then if the pelts have not been previously oiled during the tanning process, or prior to the drying, they receive thistreatment now. The oil or fat is applied to the leather side of the furs, which are then placed in the tramping machine for a short time in order to cause the oil to be forced into the skin. The fibres of the corium thus become coated with a thin layer of fatty material, which contributes greatly tothe softness and flexibility of the pelt, and increases its resistance to the action of water, and also, in certain instances a partial chamois tan is produced, thereby improving the quality of the leather.
Fig. 13Fig. 13. Stretching Machine for Cased Skins.(Reliable Machine Works, Evergreen, L. I.)
Fig. 13. Stretching Machine for Cased Skins.
(Reliable Machine Works, Evergreen, L. I.)
The skins are now returned to the work bench, and subjected to the stretching or “staking” process. This consists in drawing the skin in all directions over the edge of a dull blade, which is usually fixed upright in a post with the edge up. Or, the stretching may be done on the fleshing bench, substituting a dull blade for the fleshing knife. Recently staking machines are being used in the larger establishments, the work being done much more quickly and efficiently. As a result of this operation, the leather becomes very soft and flexible, every bit of hardness and stiffness being eliminated, and the skins receive their maximum stretch, thereby giving the greatest possible surface to the pelage. This not only helps to bring out the beauty of the hair, but is also a decided advantage from the economic point of view, as a considerable saving of material is effected in this way, sometimes even to the extent of twenty-five per cent. Cased skins are stretched in a somewhat different manner, by means of stretching irons. These consist of two long iron rods joined by a pivot at one end. The skins are slipped on to the irons, which are then spread apart, and in this way the skins are stretched and softened. A machine which does this work very efficiently is shown inFig. 13.The skin is drawn onto the stretching arms, in this case made of bronze, which are then forced apart by pressing on a pedal. When properly stretched to the maximum width in all directions possible, and thus thoroughly softened, the skin can easily be reversed, that is, turned hair-side out. As many as 6000 skins can be stretched, or 4000 to 5000 skins stretched and reversed by one man in one day on such a machine.
Fig. 14Fig. 14. Fur Beating Machine.(S. M. Jacoby Co., New York.)
Fig. 14. Fur Beating Machine.
(S. M. Jacoby Co., New York.)
The pelts are then combed and beaten. In smaller plants these operations are done by hand, but suitablemachines are being employed. In order to straighten out the hair, it is combed or brushed. Then in order to loosen up the hair, and to cause it to display its fullness, the furs are beaten. This process is also done by hand in some establishments, but up-to-date places use mechanical devices for this purpose. A type of machine which has proven very successful, and is enjoying considerable popularity is shown inFig. 14. These machines are also made with special suction attachments which remove all dust as it comes out of the beaten skin, thereby making this formerly unhealthful operation thoroughly sanitary and hygienic.
The final process is drum-cleaning. This operation is intended specifically for the benefit of the hair part of the fur, and is very important inasmuch as the attractive appearance of the fur depends largely upon it. The drum, such as is shown inFig. 15is generally made of wood, or sometimes of wood covered with galvanized iron. The skins together with fine hardwood sawdust are tumbled for 2 to 4 hours, or sometimes longer. Occasionally a little asbestos or soapstone is added to the sawdust; for white, or very light-colored skins, gypsum or white sand is used, either alone, or in admixture with the sawdust; and for darker skins, graphite or fine charcoal is sometimes added in small quantities. The drum-cleaning process polishes the hair, giving it its full gloss and lustre, and at the same time absorbing any oil or other undesirable matter which may be adhering to the hair as a result of the washing and tanning processes. Any soap, or traces of mordant are wiped off and so removed, and by using heated sawdust, or heating the drum while rotating, the fur acquires a fullness and play of the hair which are great desiderata in furs. The sawdust must then be shaken out of the furs. This is done by cageing. In some instances, the drum itself can be converted into a cage, by replacing the solid door with one made of a wire screen. (Fig. 16.) Usually, however, the skins are removed from the drum and put in a separate cage, which is builtlike the drum, but has a wire net all around it, through which the sawdust falls, while the skins are held back. The cages are generally enclosed in compartments in order to prevent the sawdust from flying about and forming a dust which would be injurious to the health of the workers. In large establishments, the drum-cleaning machinery occupies a large section of the plant, many drums and cages being used, and special arrangements being made to take care of the sawdust which can be used over again several times, until it becomes quite dirty.
Fig. 15Fig. 15. Drum. (Combination Drum and Cage as a Drum.)(F. Blattner, Brooklyn, New York.)
Fig. 15. Drum. (Combination Drum and Cage as a Drum.)
(F. Blattner, Brooklyn, New York.)
Fig. 16Fig. 16. Cage. (Combination Drum and Cage as a Cage.)(F. Blattner, Brooklyn, New York.)
Fig. 16. Cage. (Combination Drum and Cage as a Cage.)
(F. Blattner, Brooklyn, New York.)
With this operation ends the ordinary procedure of fur dressing. But there are several additional processes required in the treatment of certain furs, which are generallyundertaken by the dresser, and chief among these are shearing and unhairing. Sometimes this work is done in separate establishments organized solely for this business. Certain kinds of furs, among them being seal, beaver and nutria, possess top-hair which may detract from the beauty of the fur, the true attractiveness being in the fur-hair. The top-hairs are therefore removed, and for this purpose machines are now being used. Formerly this work was all done by hand, and on the more expensive furs like seal and beaver, unhairing is now done on a machine operated by hand. The principle of the process is as follows: The skins are placed on a platform and the hair blown apart bymeans of a bellows. The stiff top-hairs remain standing up, and sharp knives are brought down mechanically to the desired depth, and the hair is cut off at that point. The skin is then moved forward a short distance, and the process repeated until all the top-hairs have thus been cut out. With muskrats, or other pelts which do not require such very careful attention, the whole process is done automatically on a machine. The fur-hair is brushed apart by means of brushes and a comb, and at regular intervals, sharp knives cut off the top-hairs. Several hundred skins can be unhaired in a day on such a machine requiring the attention of only one man. A machine for unhairing skins is shown inFig. 17.
Fig. 17Fig. 17. Unhairing Machine.(Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.)
Fig. 17. Unhairing Machine.
(Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.)
With other furs, such as rabbits, hares, etc., where the trouble of unhairing would be too great commensurate withits advantages, the hair is sheared instead. The top hair is cut down to the same length as the under-hair by means of shearing machines which can be regulated to cut to any desired length of hair. A typical device for shearing furs is shown inFig. 18.
Fig. 18Fig. 18. Fur-Shearing Machine.(Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.)
Fig. 18. Fur-Shearing Machine.
(Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.)
The assertion has often been made, although its absurdity is now quite generally realized, that the success of the European fur dressers and dyers, particularly in Leipzig, is due to the peculiar nature of the water used, which is supposed to be especially suited for their needs. The achievements in this country in the fur dressing and dyeing industry during the past few years are ample and sufficient answers to the claim of foreign superiority in this field no matter what reason may be given, and particularly when the quality of the water used is advanced as a leading argument. For the water employed by the establishments in and about New York, as well as in other sections of the country is surely not the same as the water of Leipzig, yet the work done here is in every respect the equal of, if not better than the foreign products.
It is interesting to note that similar rumors were current here in the early period of the development of the American coal-tar industry since 1914. Our efforts to establish an independent dyestuff industry were doomed to failure, according to those who circulated the stories, because we did not have the water, which they claimed was responsible for the German success. The present status of the American dye business, in its capacity satisfactorily to supply most of the needs of this country and of others as well, speaks for itself.
However, as is often the case with such erroneous assertions, there is just enough of an element of truth in the statement regarding the peculiar qualities of certain kinds of water, to make the matter worthy of consideration.Water is certainly a factor of great importance in fur dressing and dyeing, and it is not every sort of water that is suitable for use. This fact was recognized by the early masters of the art, for they invariably used rain-water as the medium for their tanning and dyeing materials, and their choice must be regarded as an exceedingly wise one. While the necessity for giving consideration to the quality of the water for fur dressing purposes is great, it is in fur dyeing that the effects of using the wrong water are largely evident, and so extra care must be exercised in the selection of water for this purpose.
The essential requirements for a water suitable for the needs of the fur dressing and dyeing industry, are: first, a sufficient, constant and uniform supply; and second, the absence of certain deleterious ingredients. Chemically pure water is simply the product of the combination of two parts by volume of hydrogen with one part by volume of oxygen. Such water can only be made in the laboratory, and is of no importance in industry. For practical purposes, distilled water may be regarded as the standard of pure water. Here, too, the cost and trouble involved in the production of distilled water on a large scale is warranted only in a certain few industrial operations. A natural source of water which in its character most nearly approaches distilled water is rain. In fact, rain-water is a distilled water, for the sun’s heat vaporizes the water from the surface of the earth forming clouds, which on cooling, are condensed and come down as rain. Rain-water is usually regarded as the purest form of natural water. Exclusive of the first rain after a dry period, rain-water is quite free of impurities, except possibly for a small percentage of dissolved atmospheric gases, which are practically harmless, and which can usually be readily eliminated by heating the water. Moreover, rain-water is quite uniform in its composition throughout the year in the same locality, and it possesses all the desirable qualities of a water suited for fur dressing anddyeing purposes. Formerly when the quantity of water used in the industry was comparatively small, the supply from rain was sufficient to meet all the requirements. But now, when tremendous quantities of water are used constantly, rain-water is no longer a feasible source, and other supplies must be utilized, although in a sense, all water may be traced to rain-water as its origin.
When rain-water falls on the earth it either sinks into the ground until it reaches an impervious layer, where it collects as a subterranean pool, forming a well, or continues to flow underground until it finally emerges at the surface as a spring; or on the other hand the rain-water may sink but a short distance below the surface, draining off as ponds, lakes or rivers. In the first case the water is called ground water, in the latter it is known as surface water. Ground water usually contains metallic salts in solution, and relatively little suspended matter. If the water has percolated through igneous rocks, like granite, it may be quite free even of dissolved salts, and such water is considered “soft.” If, however, the rocky formations over which, or through which, the water has passed contain limestone or sandstone, or the like, salts of calcium and magnesium will be dissolved by the water. The presence of the lime and magnesia salts, as well as salts of aluminum and iron, in the water, causes it to be what is termed “hard.” Surface water is more likely to contain suspended matter, with very little of dissolved substances. Suspended matter, like mud, contains much objectionable matter such as putrefactive organisms and iron, but most of these materials can be removed by filtration or sedimentation, and seldom cause any difficulties.
Hardness in water is generally the chief source of trouble when the water is at fault. Hardness may be of two kinds, either permanent, or temporary, or sometimes both are found together. Water which is permanently hard usually contains the lime and magnesia combined as sulphates.Temporary hardness, on the other hand, is due to the presence of lime and magnesia in the form of bicarbonates, the carbon dioxide contained in the water having dissolved the practically insoluble carbonates:
Temporary hardness can be eliminated by heating the water, the carbon dioxide being expelled and the carbonates of lime and magnesia being precipitated and then filtered off. Both permanently and temporarily hard waters can be softened by the addition of the proper chemical, such as an alkaline carbonate like sodium carbonate. This precipitates insoluble carbonates of the lime, magnesia, iron and aluminum, leaving a harmless salt of sodium in solution in the water. The sludge is allowed to settle in tanks before the water is used.
In fur dressing and dyeing, water is employed for soaking and washing the skins, dissolving chemicals, extracts and dye materials, and also for steam boilers. A small amount of hardness in the water is not harmful, and up to 10 parts of solid matter per 100,000, may be disregarded. Permanent hardness is particularly objectionable in water for boiler purposes, as it forms scale. The effect of the impurities of the water depends on the nature of the chemicals and dyes used. Where acids are used in solution compounds of magnesium, lime and aluminum will generally not interfere. Hard water must not be used for soap solutions, as sticky insoluble precipitates are formed with the soap by the metals, this compound adhering to the hair, and being difficult to remove, will cause considerable trouble in subsequent dyeing. An appreciable loss of soap also results, as one part of lime, calculated as carbonate will render useless twelve parts of soap. In tanning or mordanting, where salts of tin, aluminum or iron are employed, hard water should not beused, as lime and magnesia will form precipitates with them. Bichromates will be reduced to neutral salts, and cream of tartar will also be neutralized. With dyes also, hard water has a deleterious effect. Basic dyes are precipitated by this kind of water, rendering part of the dye useless, and also causing uneven and streaky dyeings. Sometimes the shades of the dyeings are modified or unfavorably affected. Considerable quantities of lime and magnesia in the water will cause duller shades with logwood and fustic dyeings. The presence of iron, even in very slight quantities generally alters the shade, darkening and dulling the color.
These facts were apparently all recognized and understood by the fur dressers and dyers of an earlier period, for instead of utilizing the water of lakes and streams near at hand, which afforded a more constant supply, but which contained harmful impurities, they collected the rain-water, which was always soft. Whether they realized the nature and character of the substances that make water hard is uncertain, but they were always careful to avoid such water. At the present time establishments located in and about large cities like New York, where the majority of American fur dressing and dyeing plants are situated, have no trouble about the water. The cities supply water which is soft, suitable alike for drinking and industrial purposes. Other plants, not so fortunately situated, often have to employ chemical means to treat the water so as to make it suitable for use.
In discussing fur dyeing, the question naturally arises, “Why dye furs at all? Are not furs most attractive in their natural colors, and therefore more desirable than those which acquire their color through the artifices of man?” The answer cannot be given simply. Natural furs of the more valuable kinds are indeed above comparison with the majority of dyed furs. Yet there are several reasons which fully justify and explain the need for fur dyeing, for at the present time, this branch of the fur industry is almost as important and indispensable as the dressing of furs.
The first application of dyeing to furs, had for its purpose the improvement of skins which were poor or faulty in color; or rather, the object was to hide such defects. As nearly as can be ascertained, this practise was instituted at some time during or before the fourteenth century, for fur dyeing seems to have been common during that period, as is apparent from the verses of a well-known German satirist, Sebastian Brant, who lived in the latter part of the fourteenth century: