Corn oil1,000partsPotash lye, 31-1/2 degs. B.697parts
Proceed as in the directions just given for textile soap in placing charge in the kettle. When the kettle is boiling up well, shut off the steam and the saponification will complete itself. The soap may be run into the barrels the next day.
A heavy soap with a smaller percentage of fat may be made as follows:
Corn oil1,000partsPotash lye, 24-1/2 degs. B.900parts
Boil until the soap bunches, and shovel the finished soap into barrels. Upon standing it will clear up. By the addition of more water the yield of soap per pound of oil may be run up to 300 per cent.
After soft soaps have been allowed to stand for some time the phenomenon known as "figging" often occurs. This term is applied to a crystalline-like formation, causing spots of a star-like shape throughout the soap. This is undoubtedly due to the stearine content of the soap crystallizing out as it cools, and forming these peculiarly-shaped spots. It more generally occurs in the winter and may be produced artificially by adding a small quantity of soda to the potash lye before saponification.
The oils usually employed in the manufacture of potash soaps are cottonseed oil, corn oil, soya bean oil, olive oil foots, red oil, cocoanut oil, grease and the various train oils. The usual percentage yield is from 225 per cent. to 300 per cent., based upon the weight of oil used. In calculating the weight of a soft soap it is to be remembered that since potassium has a higher molecular weight (56) than sodium (40), the corresponding soap formed is that much greater in weight when compared with a sodium soap. Rosin may be added to soft soaps as a cheapening agent.
The cold process for manufacturing soap is the simplest method of soap making, and the equipment required is small when compared to the other methods. All the more expensive equipment that is necessary is a crutcher, a tank to hold the lye, frames, a slabber or cutting table, and a press. Yet, in spite of the simplicity of thus making soap, the disadvantages are numerous for the production of a good piece of soap. The greatest difficulty is to obtain a thorough combination of oil or fat and lye so that there will not be an excess of one or the other in the finished soap. At its best there is either a considerable excess of free fat which later exhibits itself in producing rancidity or uncombined caustic, which produces an unpleasant effect on the skin when the soap is consumed for washing. The latter objection, of course, can only be applied to toilet soaps.
Cocoanut oil is used very largely in the manufacture of cold-made soaps as it is well adapted for this purpose, although it is by no means true that other oils may not be employed. Since by this process of manufacture no impurity contained in the fat or oil is removed in the making of the soap, it is necessary that in order to obtain a fine finished product, any impurity contained in these may be removed if present, or that the fats be as pure as can be obtained. If inedible tallow is used for cold-made soap, it is advisable to bleach it by the Fuller's Earth Process.
The carrying out of this method is best illustrated by an example of a cold-made cocoanut oil soap.
Charge:Cochin cocoanut oil846partsLye (soda), 35 degs. B.470partsWater24parts
The oil is run into the crutcher and the temperature of the oil raised to 100 degs. F. by dry steam. The lye and water are at room temperature. After all the oil is in the crutcher, the lye and water are slowly added to prevent any graining of the soap. Toward the end the lye may be added more rapidly. When all the lye is in, the mass is crutched for about three hours, or until upon stopping the crutcher a finger drawn over the surface of the soap leaves an impression. If this condition is not realized, the soap must be mixed until such is the case. Having arrived at this point, the mixture is dropped into a frame which should remain uncovered. The heat produced by the further spontaneous saponification will cause the soap to rise in the middle of the frame. After having set for some days it is ready to be slabbed and cut into cakes.
A potash soap may be made by the cold process just as readily as a soda soap. Soaps of this type may be made by either of these formulae in a crutcher:
Olive oil foots600Potash lye, 18 degs. B. hot, 20 degs. B. cold660
or
Corn oil800Rosin200Potash lye, 27 degs. B.790Water340
Heat the oils to 190 degs. F., add the lye and crutch until the soap begins to bunch, when it is ready to be run into barrels where the saponification will be completed.
Semi-boiled soaps differ from those made by the cold process in temperature. In making semi-boiled soaps the fats are usually heated to 140° F. The addition of thelye raises the temperature to 180°—200° F. when saponification takes place.
The method of the formation of soap by the utilization of the fatty acid directly, from which the glycerine has already been removed by some method of saponification other than with caustic soda, and neutralizing this with alkali, is becoming increasingly popular. The glycerine is more easily recovered from a previous cleavage of the fats or oils, but a soap made from the mixed fatty acids thus obtained is seldom white in color and retains an unpleasant odor. Since soda ash or sodium carbonate is cheaper than caustic soda and readily unites with a fatty acid, it is used as the alkali in the carbonate saponification. The process is similar to that already given under Rosin Saponification. About 19 per cent. by weight of the fatty acids employed of 58 per cent. soda ash is dissolved in water until it has a density of 30 degs. B., and the solution is run into the kettle, which is usually equipped with a removable agitator. The fatty acids, previously melted, are then slowly added while the mixture is boiled with open steam and agitated with the stirring device. The fatty acids instantly unite with the carbonate and rise in the kettle, due to the generation of carbon dioxide, and care must be exercised to prevent boiling over. After all the fatty acid has been added, and the mass is boiled through the saponification must be completed with caustic soda, as there is as yet no practical method known which will split a fat entirely into fatty acid and glycerine. Thus about 10 per cent. of the fatty acids are true neutral fats and require caustic soda for their saponification. This is then added and the soap completed, as in full-boiled soaps.
In carrying out this method upon a large scale, largesue\Neanderthal\doroteer\Neanderthal\Josephine\ quantities of carbon dioxide are formed during the boiling of the soap, which replaces a quantity of the air contained therein. The kettle room should therefore be well ventilated, allowing for a large inflow of fresh air from out of doors.
In considering the many different varieties of soaps, their classification is purely an arbitrary one. No definite plan can be outlined for any particular brand to be manufactured nor can any very sharp distinction be drawn between the many soaps of different properties which are designated by various names. It is really a question to what use a soap is to be put, and at what price it may be sold. There is, of course, a difference in the appearance, form and color, and then there are soaps of special kinds, such as floating soaps, transparent soaps, liquid soaps, etc., yet in the ultimate sense they are closely allied, because they are all the same chemical compound, varying only in their being a potash or soda soap, and in the fatty acids which enter into combination with these alkalis. Thus we can take a combination of tallow and cocoanut oil and make a great many presumably different soaps by combining these substances with caustic soda, by different methods of manufacture and by incorporating various other ingredients, as air, to form a floating soap, alcohol to make a transparent soap, dyestuffs to give a different color, etc., but essentially it is the same definite compound.
The manufacturer can best judge the brand of soaps he desires to manufacture, and much of his success depends upon the name, package, shape, color or perfume of a cake of soap. It is the consumer whom he must please and many of the large selling brands upon the market today owe their success to the above mentioned details. The great majority of consumers of soap know very littleconcerning soap, except the fact that it washes or has a pleasant odor or looks pretty, and the manufacturer of soap must study these phases of the subject even more carefully than the making of the soap itself.
For a matter of convenience we will classify soap under three general divisions:
I. Laundry soaps, including chip soaps, soap powders and scouring soaps.
II. Toilet soaps, including floating soap, castile soap, liquid soap, shaving soap, etc.
III. Textile soaps.
The most popular household soap is laundry soap. A tremendous amount of this soap is consumed each day in this country, and it is by far manufactured in larger quantities than any other soap. It is also a soap which must be sold cheaper than any other soap that enters the home.
The consumers of laundry soap have been educated to use a full boiled settled rosin soap and to make a good article at a price this method should be carried out, as it is the one most advisable to use. The composition of the fats entering into the soap depends upon the market price of these, and it is not advisable to keep to one formula in the manufacture of laundry soap, but rather to adjust the various fatty ingredients to obtain the desired results with the cheapest material that can be purchased. It is impossible to use a good grade of fats and make a profit upon laundry soap at the price at which it must be retailed. The manufacturer of this grade of soap must look to the by-product, glycerine, for his profit and he is fortunate indeed if he realizes the entire benefit of this and still produces a superior piece of laundry soap.
It is advantageous at times to make a laundry soap by a method other than the full boiled settled soap procedure as previously outlined. This is especially the condition in making a naphtha soap, in which is incorporated naphtha, which is very volatile and some of the well known manufacturers of this class of soap have adopted this process entirely. A laundry soap containing rosin cannot be advantageously made by the cold process, as the soap thus made grains during saponification and drops a portion of the lye and filling materials. By making a semi-boiled soap this objection is overcome. The half boiled process differs from the cold process by uniting the fats and alkalis at a higher temperature.
To carry out this process the following formulae have been found by experience to give satisfactory results.
I.lbs.Tallow100Rosin60Soda Lye, 36° B.80II.Tallow100Rosin60Silicate of Soda25Soda Lye, 36° B.85III.Tallow100Rosin100Lye, 36° B.105Silicate of Soda25Sal Soda Solution20
In any of these formulas the sodium silicate (40° B.) may be increased to the same proportion as the fats used. By so doing, however, twenty pounds of 36° B. lye must be added for every hundred pounds of silicate additional to that indicated or in other words, for every pound of silicate added 20 per cent. by weight of 36° B. lye must be put into the mixture. The rosin may also be replaced by a previously made rosin soap.
To make a semi-boiled soap, using any of the above formulae, first melt the rosin with all or part of the fat, as rosin when melted alone readily decomposes. When the mixture is at 150° F. run it into the crutcher and add the lye. Turn on sufficient dry steam to keep the temperature of the soap at about 150° F. in the winter or 130° F. in summer. After the mass has been mixed for half an hour, by continuously crutching the soap it will at first thicken, then grain and it may again become thick before it becomes smooth. When the mass is perfectly smooth and homogeneous drop into a frame and crutch in the frame by hand to prevent streaking. After standing the required length of time the soap is finished into cakes as usual.
Settled rosin soaps are made from tallow, grease, cottonseed oil, bleached palm oils of the lower grades, corn oil, soya bean oil, arachis oil, distilled garbage grease, cottonseed foots or fatty acids together with an addition of rosin, varying from 24 per cent. to 60 per cent. of the fatty acids which should titer from 28 to 35. A titer lower than 28 will prevent the finished kettle of soap from being capable of later taking up the filling materials. As has already been stated under hardened oils, these being very much higher in titer allow a greater percentage of rosin to be added. Thus hardened fish oils and cottonseed oil aregradually being more extensively employed in soaps of this character.
The procedure of handling the kettle is similar to that given under full boiled soap. The stock is steamed out into a settling tank and allowed to settle over night, after which it is pumped into the soap kettle. Having stocked the kettle, open steam is turned on and 10°-12° B. lye is run in, while using a steam pressure of ninety to one hundred pounds in order to prevent too great a quantity of condensation of the steam, the water thus being formed weakening the lye. If a steam pressure of fifty to sixty pounds is available, a stronger lye (20° B.) should be added. Care must be taken not to allow the lye to flow in too rapidly or the soap will not grain. The saponification is only attained by prolonged boiling with sufficient lye of proper strength. When saponification has taken place, the mass begins to clear and a sample taken out with a paddle and cooled should show a slight pink with a 1 per cent. alcoholic phenolphthalein solution.
It may be stated here that in using this indicator or any other to test the alkalinity of soap, the soap should always be cooled and firm, as whenever water is present, the dissociation of the soap thereby will always react alkaline. When this state is reached the mass is ready for graining, which is accomplished by distributing salt brine or pickle or spreading dry salt over the surface of the soap. The kettle is then thoroughly boiled until the mass shows a soft curd and the lye drops clearly from a sample taken out with a trowel or paddle. The steam is then shut off and the soap allowed to settle over night. The lyes are then run off to the spent lye tank for glycerine recovery. In saponifying a freshly stocked kettle it is apt to bunch. To prevent this salt is added at various times to approximately one per cent. of the fat used.
If, by any possibility the soap has bunched, this condition may be remedied by the addition of more strong lye and boiling until it is taken up. To work a kettle to its full capacity it is advisable to make two "killing" changes. First add about 75 per cent. of the fat and grain as directed. Run off the spent lyes and then add the remainder of the stock and repeat the process. When the spent lye has been run to storage, the open steam is again turned on and 18° B. lye gradually allowed to run in. The rosin is now broken up and put into the kettle, or a previously made rosin soap is pumped in.
Lye is then added until the soap has a sharp taste after about three hours of continuous boiling, or when the soap is in the closed state. More lye should then be run into the kettle to grain the soap well, the grain not being too small. Then allow the soap to settle over night and draw off the strengthening lye. The next day again boil up the kettle and add water until the soap thins out and rises or swells high in the kettle. A sample taken out at this stage upon a hot trowel should run off in large flakes. The surface of the soap should be bright and shiny.
If the sample clings to the trowel, a slight addition of lye will remedy this defect. The kettle is then allowed to rest, to drop the nigre and to cool for some time, depending upon the size of the kettle. The proper temperature is such that after having been pumped to the crutcher and the filling materials having been added, a thermometer placed into the mass should indicate 128°-135° F. after the crutcher has run from ten to fifteen minutes. The filling material may consist of from 7-9 per cent. of sal soda solution, 36°-37° B. warm or just enough to close up the soap and make it rise high in the center of a screw crutcher and make it cling close to a warm trowel. Other fillers such as outlined below are added at this point.
An addition of from 2-3 per cent. of a special mineral oil for this purpose will impart a finish to the soap and 3-5 per cent. starch added prevents the soap from cracking in the frames. Other filling material as silicate of soda, borax, talc or silex are used. After the filling material has been thoroughly crutched through the soap it is framed, and, after being several days in the frame to solidify and cool the soap is ready for slabbing, pressing and wrapping.
In order to more definitely illustrate the composition of the mixture of fats and oils entering into the formation of a laundry soap a typical formula may be given for such a soap containing 40 per cent. rosin added to the amount of fats used:
lbs.Grease7,000Tallow4,000Corn Oil7,000Cottonseed Oil3,000Rosin8,400
The following have been found to be satisfactory filling materials and are calculated upon the basis of a 1,400-pound frame of soap.
I.lbs.Sodium Silicate, 38°-40° B.100Mineral Oil25Sal Soda Solution, 36° B.80Borax1II.Sal Soda Solution, 36° B.80Mineral Oil25Sodium Silicate60III.Soda Ash10Sal Soda55Sodium Silicate115Mineral Oil40Brine (Saturated Solution)10Sodium Silicate, 38°-40° B.100IV.Sodium Silicate100Silex or Talc200Soda Ash50V.Sal Soda Solution, 36° B.90Sodium Silicate50-60Mineral Oil25Borax Solution, 25° B. (hot)15
Chip soap is used extensively in laundries but is also used largely in other branches. It may be made either as a settled soap or by the cold made process.
To make a full boiled settled chip soap, proceed as directed under settled laundry soap. The kettle is stocked with light grease or a mixture of grease with corn oil or other cheap oils. For this kind of soap the rosin is eliminated.
Chip soap may be filled as well as laundry soap. This is done in the crutcher and the following adulterations are suitable.
lbs.Settled Soap700Soda Ash35Sodium Silicate215orSettled Soap700Silicate of Soda560Soda Ash18Carbonate of Potash, 26° B.50
The cheapest method of drying is by running this soap through a drying machine and this is the procedure usually carried out for making dried chip soap.
To make chip soaps by the cold process a sweet tallow of low percentage of free fatty acid should be employed. The tallow is heated to 120° to 135° F. and the lye run in slowly at first and then the silicate of soda is added. The mass is then mixed until a finger drawn through the soap leaves a slight impression, then dropped into frames or barrels. Soaps containing a small percentage of fat should be well covered in the frame for twenty-four hours to retain their heat and insure proper saponification. The following formulae are suitable:
I.lbs.Tallow1,200Soda Lye, 35° B.850Sodium Silicate750II.Tallow475Ceylon Cocoanut Oil100Soda Lye, 37° B.325Potash Lye, 37° B.56III.Tallow500Soda Lye, 37-1/2° B.297Sodium Silicate416Potash Lye, 37-1/2° B.37-1/2IV.Tallow450Soda Lye, 37-1/2° B.255Sodium Silicate450Potash Lye, 37-1/2° B.50V.Tallow450Soda Lye, 35° B.470Sodium Silicate650VI.Tallow420Sodium Silicate600Soda Lye, 37-12° B.270
A very good grade of chip soap is made by employing no filling material whatsoever, but unfortunately the price of this soap has been cut to such an extent that these can not compete with a filled chip. A number of the best soaps of this kind are made from a settled soap using a light grease with corn oil. A soap of this nature is made as follows.
lbs.Settled Soap800Sal Soda Solution, 36°-37° B.252Soda Ash182
If this soap is run into frames it may be stripped and chipped in two days.
Soap powders have become so great a convenience as a general cleansing agent that to eliminate them from the household necessities would mean much unnecessaryenergy and work to the great number of consumers of this product. They may be manufactured so cheaply and still be efficient, that their use has almost become universal for cleansing and scouring purposes. The uses to which soap and scouring powders are adapted are too well known to enter into a description of their employment. Since they offer a greater profit to the manufacturer than ordinary household soap, many brands are extensively advertised.
Numerous combinations for soap powders might be cited and it is a simple matter to vary the ingredients as to fat content and manufacture a powder of this sort as low as a cent a pound. Many substances are incorporated with soap, such as salt, soda ash, tripoli, crushed volcanic deposits, ground feldspar, infusorial earth of various kinds, silex, etc. In addition to these various fillers, compounds with true cleansing and bleaching properties, in addition to soap, are added, such as the salts of ammonium (sal ammoniac, carbonate of ammonia), sodium perborate and the peroxides of various metals. The public, however, have been accustomed to receive a large package of soap or scouring powder for a small amount of money and it is a difficult matter for the manufacturer to add more expensive substances of this nature to his product, to increase its efficiency, without raising the price or decreasing the size of the package.
In manufacturing soap powders, the dried soap chips might be mixed with the filler and alkali and then pulverized. This method is not extensively employed nevertheless. The process which is the most economical is one whereby the ingredients are mixed in a specially adapted mixer for heavy material until dry and then run directly to the crusher and pulverizer, after which it is automatically packed, sealed and boxed.Another method of procedure is to run out the mixture from the crutcher to the frames, which are stripped before the soap cools, and is cut up at once, for if it hardens it could not be cut with wires. It is better, however, to run the mixture into sheets upon a specially constructed floor and break up the mass when cool.
Formulae for soap powders which have been found to be suitable for running dry in the mixer follow:
ISoda ash, 58 per cent.42lbs.Silica220"Settled soap (usually cottonseed).25"Salt10"IISoap (settled cottonseed)40lbs.Soda ash, 58 per cent.60"IIISettled soap100lbs.Soda ash, 58 per cent.400"
Fillers in varying proportions may replace the soda ash in the above formulae. It is of course understood that the soap has been previously made and run as molten soap into the crutcher.
The following soap powders will not dry up in the crutcher upon running, but are of the class which may be framed or run on the floor to solidify:
ISoap850lbs.Filler400"Sal soda solution, 20 degs. B170"IISoap650lbs.Filler550"Sal soda solution, 20 degs. B.340"IIISoap80lbs.Filler550"Sal soda solution170"IVSoap (settled tallow)800lbs.Filler400"Sal soda solution170"Water100"
V
First saponify 100 parts house grease and 100 parts ordinary grease and make a run soap. Then use in crutcher either:
Soap400lbs.Filler575"Hot water60"orSoap200lbs.Hot water200"Filler625"
It would be a simple matter to write numerous additional formulae, but the above are typical. The manufacturer must judge for himself just what filling material to use. The filler indicated in the above formulae is therefore left open. A few formulae for more expensive powders than those given recently appeared among others in the "Seifensieder Zeitung"[9]:
IPowdered soap90lbs.Sodium perborate10"
The perborate should be added when the powder is perfectly dry or it loses its bleaching properties.
IISoap powder, 20 per cent. fat.Cocoanut oil fatty acids25lbs.Olein25"Bone fat70"Soda lye, 30 degs. B.90"Water150"Ammonium carbonate125"IIISoap powder, 10 per cent. fat.Cocoanut oil fatty acids20lbs.Olein10"Bone fat20"Soda lye, 30 degs. B.30"Water175"Ammonium carbonate175"
Light or fluffy powders containing 35-45% moisture can be made in two ways. The first method requiring a minimum equipment is to mix the powder and sal soda in a mixer, allow it to stand in frames for a week to crystallize or spread it on the floor for a few hours to dry and then grinding it.
The continuous method finishes the powder in a few minutes and with a minimum amount of labor. By this process the various ingredients, soap, soda ash solution, etc., are measured, run by gravity into the mixer, mixed and the molten mass run over the crystallizer or chilling rolls thruwhich either cold water or brine is pumped. From the roll the powder is scraped off clean by a knife, passes to a screen which sends the tailings to a grinder, falls into a storage bin from whence it is weighed and packed by an automatic weighing machine into cartons made up in most cases by another machine. Due to the large percentage of moisture contained in these soap powders the carton is generally wrapped in wax paper to aid in the prevention of the escape of moisture.
Scouring powders are very similar to soap powders and differ only in the filler used. We have already considered these fillers under scouring soap, from which they do not differ materially. They are usually insoluble in water to aid in scouring. The mixer used for substances of this kind in incorporating the soap and alkali must be of strong construction.
Scouring soaps resemble soap powders very closely in their composition, in that they are a combination of soap and filling material. Since more lather is required from a scouring soap than in soap powders, a cocoanut oil soap is generally used. The usual filling material used is silex. The greatest difficulty in the manufacture of scouring soap is the cracking of the finished cake. This is usually due to the incorporation of too great an amount of filler, or too high a percentage of moisture.
In manufacturing these soaps the cocoanut oil is saponified in the crutcher with 38 degs. B. lye, or previously saponified as a run soap, as already described under "Marine Soaps." To twenty-five parts of soap are added a percentage of 38 degs. B. sal sodaor soda ash solution, together with a small quantity of salt brine. To this mixture in the crutcher seventy-five parts of silex are then added, and a sufficient amount of hot water to make the mass flow readily. Care must be exercised to not add too great a quantity of water or the mass will crack when it cools. The mass is then framed and cut before it sets, or poured into molds and allowed to set. While silex is the most extensively used filler for scouring soaps, it is feasible to incorporate other substances of like character, although it is to be remembered that the consumer is accustomed to a white cake, such as silex produces. Any other material used to replace silex should also be as fine as this product.
Floating soap occupies a position midway between laundry and toilet soap. Since it is not highly perfumed and a large piece of soap may be purchased for small cost, as is the case with laundry soap, it is readily adaptable to general household use. Floating soap differs from ordinary soap in having air crutched into it which causes the soap to float in water. This is often advantageous, especially as a bath soap, and undoubtedly the largest selling brand of soap on the American market today is a floating soap.
In the manufacture of floating soap a high proportion of cocoanut oil is necessary. A most suitable composition is one part cocoanut oil to one part of tallow. This is an expensive stock for the highest grade of soap and is usually cheapened by the use of cottonseed or various other liquid oils. Thus it is possible to obtain a floating soap from a kettle stocked with 30 per cent. cocoanut oil, 15 per cent. cottonseed oil and 55 per cent. tallow. With this quality of soap, however, there is a possibility of sweating andrancidity, and of the soap being too soft and being poor in color.
The process of manufacture is to boil the soap in an ordinary soap kettle, after which air is worked into the hot soap by a specially constructed crutcher, after which the soap is framed, slabbed, cut into cakes and pressed.
Concerning the boiling of the soap, the saponification must be carefully carried out, as the high proportion of cocoanut oil may cause a violent reaction in the kettle causing it to boil over.
The method of procedure is the same as for a settled soap up to the finishing. When the mass is finally settled after the finish, the soap should be more on the "open" side, and the object should be to get as long a piece of goods as possible.
Due to its high melting point, a much harder crust forms on the surface of a floating soap and in a greater proportion than on a settled soap during the settling. In a large kettle, in fact, it has been found impossible to break through this crust by the ordinary procedure to admit the skimmer pipe. Much of the success of the subsequent operations depends upon the completeness of the settling, and in order to overcome the difficulties occasioned by the formation of the crust everything possible should be done in the way of covering the kettle completely to enable this period of settling to continue as long as possible.
When the soap is finished it is run into a specially constructed U-shape crutcher, a Strunz crutcher is best adapted to this purpose, although a rapidly revolving upright screw crutcher has been found to give satisfaction upon a smaller scale, and a sufficient quantity of air beaten into the soap to make it light enough to float. Care must be taken not to run the crutcher too rapidly or the soap will be entirely too fobby. During this operation the mass ofsoap increases in bulk, and after it has been established how much air must be put into the soap to satisfy the requirements, this increase in bulk is a criterion to estimate when this process is completed.
It is of course understood that the longer the crutching continues the greater quantity of air is incorporated and the increase of volume must be established for a particular composition by sampling, cooling the sample rapidly and seeing if it floats in water. If the beating is continued too long an interval of time, the finished soap is too spongy and useless.
The temperature of the mass during crutching is most important. This must never exceed 158 degrees F. At 159 degrees F. the operation is not very successful, yet the thermometer may indicate 140 degrees F. without interfering with this operation. If, however, the temperature drops too low, trouble is liable to be met with, by the soap solidifying too quickly in the frames.
When the crutching is completed, the soap is allowed to drop into frames through the valve at the bottom of the crutcher and rapidly crutched by the hand in the frames to prevent large air spaces and then allowed to cool. It is an improvement to jolt the frames as they are drawn away as this tends to make the larger air bubbles float to the surface and thus reduce the quantity of waste. When the soap has cooled, the frame is stripped and the soap slabbed as usual. At this point a layer of considerable depth of spongy soap will be found to have formed. This of course must be cut away and returned to the kettle. The last few slabs are also often rejected, inasmuch as the weight of the soap above them has forced out so much of the air that the soap no longer floats. As a fair average it may be estimated that not more than 50 to 60 per cent. of the soap in the kettle will come out as finished cakes.the remaining 40 to 50 per cent. being constituted by the heavy crust in the kettle, the spongy tops, the bottom slabs and scrapings. This soap is of course reboiled and consequently not lost, but the actual cakes obtained are produced at a cost of practically double labor.
It is advisable to add a small quantity of soap blue color to the mass while crutching to neutralize the yellowish tint a floating soap is liable to have.
Some manufacturers add a percentage of carbonate of soda, about 3 per cent., to prevent the soap from shrinking. Floating soap may also be loaded with sodium silicate to the extent of about 5 per cent.
It is not a simple matter to differentiate between toilet soaps and various other soaps, because numerous soaps are adaptable to toilet purposes. While some soaps of this variety are manufactured by the cold made or semi-boiled process, and not milled, the consumer has become accustomed to a milled soap for general toilet use.
The toilet base most extensively employed is a tallow and cocoanut base made as a full boiled settled soap. The manufacture of this base has already been outlined and really needs no further comment except that it is to be remembered that a suitable toilet soap should contain no great excess of free alkali which is injurious to the skin. Cochin cocoanut oil is preferable to the Ceylon cocoanut oil or palm kernel oil, to use in conjunction with the tallow, which should be a good grade and color if a white piece of goods is desired. The percentage of cocoanut oil may be anywhere from 10 to 25 per cent., depending upon the kind of lather required, it being remembered that cocoanut oil increases the lathering power of the soap.
In addition to a tallow base, numerous other oils areused in the manufacture of toilet soaps, especially palm oil, palm kernel oil, olive oil and olive oil foots, and to a much less extent arachis or peanut oil, sesame oil and poppy seed oil, oils of the class of cottonseed, corn and soya bean oils are not adapted to manufacturing a milled soap, as they form yellow spots in a finished cake of soap which has been kept a short time.
Palm oil, especially the Lagos oil, is much used in making a palm base. As has already been stated, the oil is bleached before saponification. A palm base has a yellowish color, a sweetish odor, and a small quantity added to a tallow base naturally aids the perfume. It is especially good for a violet soap. The peculiarity of a palm oil base is that this oil makes a short soap. By the addition of some tallow or twenty to twenty-five per cent. of cocoanut oil, or both, this objection is overcome. It is a good plan in using a straight palm base to add a proportion of yellow color to hold the yellowish tint of this soap, as a soap made from this oil continues bleaching upon exposure to air and light.
Olive oil and olive oil foots are used most extensively in the manufacture of castile soaps. The peculiarity of an olive oil soap is that it makes a very slimy lather, and like palm oil gives the soap a characteristic odor. An olive oil soap is usually considered to be a very neutral soap and may readily be superfatted. Much olive oil soap is used in bars or slabs as an unmilled soap and it is often made by the cold process. Peanut oil or sesame and poppy seed oil often replaces olive oil, as they form a similar soap to olive oil.
In the manufacture of a toilet soap it is hardly practical to lay down a definite plan for the various bases to be made. From the combination of tallow, palm oil, cocoanut oil, palm kernel oil, olive oil and olive oil foots, a greatmany bases of different proportions might be given. The simplest method is to make a tallow base, a palm base and an olive oil base. Then from these it is an easy matter to weigh out any proportion of these soap bases and obtain the proper mixture in the mill. If, however, as is often the case, a large quantity of soap base of certain proportions of these, four or even more of these fats and oils is required, it is not only more economical to stock the kettle with the correct proportion of these oils, but a more thorough mixture is thus obtained by saponifying these in the kettle. In view of the fact that it is really a question for the manufacturer to decide for himself what combination of oils he desires for a particular soap we will simply outline a few typical toilet soap bases in their simplest combination. It is understood that these soaps are suitable for milled soaps and are to be made as fully boiled settled soaps. Palm kernel oil may be substituted for cocoanut oil in all cases.