For a small batch, 56 lb. Cochin cocoa-nut oil and 56 lb. sweet edible tallow may be taken, melted at 130° F. (54° C.), and carefully strained into a small steam-jacketed pan. It is imperative that the materials should be of the highest quality and perfectly clean. Twenty-three lb. of pure glycerine and 56 lb. of bright caustic soda solution made from high grade caustic and having a density of 72° Tw. (38° B.) are crutched into the fat; the alcohol, which would be 45 lb. in this example, is then added. The whole must be most intimately incorporated, and the pan covered and allowed to rest for one hour or one and a half hours. Saponification should ensue.
To produce a transparent glycerine soap with the aid of castor oil, and with or without the use of alcohol, the following is the procedure:—
Cochin cocoa-nut oil, sweet edible tallow, and castor oil, of each 56 lb. are taken, warmed to 130° F. (54° C.), and carefully strained into the jacketed pan. If it is desired to use glycerine and cane sugar solution, and no alcohol, the glycerine (25 lb.) is now stirred into the fats together with the requisite (83 lb.) caustic soda solution 72° Tw. (38° B.). If it is intended to use alcohol and sugar, and no glycerine, the latter is replaced by 47 lb. of alcohol, and added after the incorporation of the caustic soda lye.
The whole being thoroughly crutched, the pan is covered and saponification allowed to proceed for one hour or one and a half hours. Should the saponification for some reason be retarded, a little steam may be very cautiously admitted to the jacket of the pan, the mass well crutched until the reaction commences, and the whole allowed to rest the specified time.
Whilst saponification is proceeding, the "sugar solution" is prepared by dissolving 50 lb. cane sugar in 50 lb. water, at 168° F. (76° C.), to which may be added 5 lb. soda crystals, and any necessary colouring matter. The water used for this solution should be as soft as possible, as hard water is liable to produce opaque streaks of lime soap.
It is absolutely necessary before proceeding further to ensure that saponification is complete. A greasy, soft feel and the presence of "strength" (caustic) would denote incomplete saponification—this can only be remedied by further heating and crutching. Deficiency of caustic alkali should also be avoided, and, if more lye is required, great care must be exercised in its addition.
Saponification being completed, the sugar solution is carefully and gradually crutched into the soap; when the contents of the pan have become a homogeneous and syrupy mass, the crutching is discontinued, and the pan is covered for one hour. The heat of the soap in the pan should not exceed 170° F. (77° C.).
Having rested the necessary period, the soap will have a slight froth on the surface, but will be clear underneath and appear dark. Samples may now be withdrawn, cooled, and examined prior to framing. If the process has been successfully performed the soap will be firm and transparent, of uniform colour, and possess only a faintly alkaline taste.
If the sample be firm but opaque, more sugar solution is required; this should be added very carefully whilst crutching, an excess being specially guarded against. If the sample be soft, although transparent, and the alkaline taste not too pronounced, the soap evidently contains an excess of water, which may be remedied by the addition of a small quantity of soda ash; too much soda ash (carbonates) must be avoided, lest it should produce efflorescence.
Having examined the soap and found it to be correct, or having remedied its defects, the soap in the pan is allowed to cool to 145° F. (63° C.) and perfume added. The soap is now quickly filled into narrow frames and allowed to cool rapidly.