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.
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 foots | 600 |
| Potash lye, 18 degs. B. hot, 20 degs. B. cold | 660 |
or
| Corn oil | 800 |
| Rosin | 200 |
| Potash lye, 27 degs. B. | 790 |
| Water | 340 |
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 the lye raises the temperature to 180°—200° F. when saponification takes place.