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.
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
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.