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.
COLD PROCESS.
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 oil | 846 | parts |
| Lye (soda), 35 degs. B. | 470 | parts |
| Water | 24 | parts |
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.