Besides a soap of this type a settled tallow chip soap is used.
Soaps for wool throwing are sometimes made from olive oil foots but these are often objected to because of the sulphur-like odor conveyed to the cloth due to the method by which this oil is extracted with carbon disulphide. A potash soap hardened somewhat with soda is also used. As a formula for a suitable soap of this type this may be given.
Olive Oil Foots 12 parts Corn Oil 46 " House Grease 20 " Soda Lye, 36° B. 3 " Potassium Carbonate (dry) 5-3/4 " Potassium Hydrate (solid) 23 "
This soap is made as a "run" soap by the general directions already given for a soap thus made. The kettle is boiled with open and closed steam, adding water very slowly and aiming to obtain a 220-225 per cent. yield or fatty acid content of the finished soap of 46 per cent. When the soap is finished a sample cooled on a plate of glass should be neither slippery or short, but should string slightly. The finished soap is run directly into barrels.
A soap for wool throwing by the semi-boiled process may be made from olive oil foots in a crutcher thus:
Olive Oil Foots 600 lbs. Potash Lye, 20° B. 660 "
The oil is heated to 180° F., the lye added and the mass stirred until it bunches, when it is dropped into barrels.
For the finishing of worsted cloth soaps high in cocoanut oil or palm kernel oil are preferred. These soaps are finished very neutral, being made as settled soaps, but given an extra wash change after strengthening strongly. They are then finished as usual and run into barrels. If framed too hot, the high percentage of cocoanut oil causes mottling, which is prevented by crutching by hand until the temperature of the soap is 140°-145° F. Some typical charges, all of which are saponified with soda lye, follow:
Palm Kernel Oil 30 " Red Oil (single pressed) 70 "
Red Oil 33-1/3 " Corn Oil 33-1/3 " Cocoanut Oil or Palm Kernel Oil 33-1/3 "
Soap is used to a very large extent in silk mills, both for degumming the raw silk and in silk dyeing. Raw silk consists of the true silk fibre known as fibroin and a gummy coating, sericin, which dulls the lustre of the silk unless removed. For this purpose a slightly alkaline olive oil foots soap is best adapted, although palm oil and peanut oil soaps are sometimes used, as well as soaps made from a combination of house grease to the extent of 30 per cent., together with red oil or straight olein soaps, both of which are artificially colored green. In using house grease, if 30 per cent. is exceeded in combination with red oil, the titer is raised to such an extent that the soap does not readily rinse from the silk nor dissolve readily. They are also not advisable because they impart a disagreeable odor to the silk.