In the last method a combination of 80 per cent. tallow, very low in free acid, 20 per cent. cocoanut oil and 5 per cent. W. W. rosin is a suitable charge. The saponification and finishing is carried out as with a full boiled soap. The soap is then placed into a jacketed vessel, provided with dry-steam coils, by which the excess water is evaporated from the soap until it contains 73 per cent. fatty acids. When the thick mass reaches this stage it is framed and when cool is suitable for obtaining a semi transparency which now depends upon the number of times the soap is milled, it being, of course, inferred that no solid matter of any sort be added to the soap.
Cold Made Transparent Soap.
While transparent soaps may be made by the above general methods they are usually made by the semi-boiled or cold process. By this process a more satisfactory soap is obtained and it is more simple to carry out. A detailed description of this method is best and most easily given by using a typical formula.
| Charge: | ||
| Tallow | 193-1/2 | lbs. |
| Cochin Cocoanut Oil | 169-1/2 | " |
| Castor Oil | 89-1/2 | " |
| Soda Ash | 7-3/4 | " |
| Soda Lye, 36 degs. B. | 256 | " |
| Sugar (Cane) | 198 | " |
| Alcohol | 126 | " |
| Water (Distilled) | 80 | " |
To proceed, first place into a crutcher or jacketed kettle the oils and fat and heat to 140 degs. F. Then add the soda ash dissolved in about 30 pounds of the water, after which the lye is added and the mass stirred until a finger or stick run over the surface leaves an imprint. Where the soap has reached this stage, it is well covered and allowed to stand about two hours or until it bulges in the center, after which the rest of the water which should contain no lime or other mineral substance and which is preferably distilled water, is added. The sugar is then slowly shoveled in while the mass is stirring and finally the alcohol is poured in. The heat is then increased to 160 degs. F. by dry steam and the soap crutched until dissolved. Under no circumstances should any soap be allowed to remain above the surface of the mass on the sides of the mixer. This crutching operation consumes about one hour, and when finished the soap should stand in the vessel about half an hour when a small sample is taken out to cool. This sample should be clear and show an excess of alkali. If it is not clear more alcohol is added, if not of sufficient strength more lye put in until the desired condition is reached. The perfume and color are now added.
The soap is then framed and allowed to set after which it is cut, allowed to dry slightly and then pressed. To obtain a polished cake transparent soaps are often planed before pressing and after pressing polished with a soft cloth, dampened with alcohol. Instead of framing this soap, it is sometimes "tubed," that is to say, the soap from the crutcher is run into specially constructed tubes of a shape near that of the desired cake and allowed to cool, after which it is cut and pressed. All scraps are returned to the crutcher, but in so doing the soap is slightly darkened in color. It is advisable to expose a finished cake of transparent soap to the air for some time as by so doing it becomes clearer.
Other formulae for cold made transparent soaps made as just outlined follow:
Rosin may be added in this formula up to 20 per cent. of fats used and the tallow cut down correspondingly.