A very cheap grade of soap may be made by making a run soap and adding the filler e. g. sodium silicate in the kettle during saponification. The percentage of fatty acids may be brought down to 10 per cent., although of course a soap of this type shrinks a whole lot upon exposure.
In making a "glued up" soap the procedure is the same for making the soap itself as with a settled soap, except that the soap is finished "curd" and later filled in the crutcher. The percentage of fatty acids in a soap of this type is seldom below 50 per cent.
The method of "gluing up" a soap is best illustrated by a typical soap of this character in which the kettle is charged with the following stock.
Bleached palm oil 5 parts Distilled grease 2 " Cotton oil foots stock, 63% fatty acid 1 " Rosin 4 "
The palm oil is first run into the kettle, saponified and washed to extract any glycerine, then the rest of the fats and finally the rosin. The soap is then finished and settled as with a boiled settled soap. To assure success it is absolutely necessary that the soap settle as long a period as possible, or until the temperature is about 150 degs. F. The ideal temperature for carrying out the "gluing up" process is 140 degs. F., as at a lower temperature than this the soap is liable to cool too quickly and not be thoroughly glued up. A higher temperature than 150 degs. F. causes delay in that the soap does not properly take the filler at a higher temperature and the soap must be kept in the crutcher until the temperature drops to the right point.
The soap is run into the crutcher and the percentage of fatty acids run down to 50-55 per cent. with one of the following mixtures:
Sodium silicate, 59-1/2° B. 1 part Potassium carbonate, 51° B. 1 "
Sodium silicate, 59-1/2° B. 1 part Potassium carbonate, 51° B. 1 " Sodium sulfate, 28° B. 1 "
From 230 to 300 pounds of either of these mixtures are required for a crutcher holding 2,600 pounds of soap.
The crutching is continued until the mass is well "spiked," that is to say, a freshly broken surface of the soap, as the crutcher blade is jerked away, stands up like shattered sheets in triangular form [Transcriber's note: three triangles]), which retain their shape perfectly. When this condition is realized the soap is run into frames which are carefully crutched by hand to remove any air spaces. The surface of the soap is then smoothed down and heaped up in the center. After standing a day to contract, the surface is again leveled and a snugly-fitting board placed on the top of the soap upon which a weight is placed or upon which the workman treads and stamps until the surface is flat, thus assuring the further removal of air spaces. The soap remains in the frame from six to eight days and is then slabbed, barred and pressed by the usual method employed for soaps thus handled without milling.