SOAP • MAKERS' MACHIN ERY. There are two well-known processes of soap-making, that by long-continued boiling, and the so called "cold process." While "cold-process" soap can be made with a much simpler and cheaper plant than regularly boiled soap, it requires a higher grade of stock to make a merchantable article. and as rosin has seldom been suc cessfully used in " cold-process" soap, it is usually cheapened by adding silicate of soda. Of all fillers, sal soda is probably the must satisfactory, as it will soften hard water and does not render the soap so sharp and harsh to the skin as does an excess of uneom bined or free caustic alkali. A soap moderately tilled with sal soda will generally give better satisfac tion than a soap not filled at all. In soap kettles for boiling soap, good practice allows 25 cub. ft. content for every 1,000 lbs. of fin ished soap the kettle is to turn out in a boiling. While exact data are wanting, it is probably nearly correct to allow one horse power boiler capacity for every 1,000 lbs. of finished soap to be turned out in a single boiling. A criss-cross coil in the soap-boiling kettle is just as effective and much cheaper than a spiral one of the same heating surface.
A high-grade toilet soap can be made from cuttings a-nd scraps of a good quality of hoile0 soap, by dry remelting to get rid of excessive water. For this purpose the soap stock should have no, or but little, tilling. Cuttings and scraps of " cold-process" soap, especially if filled with silicate of soda, cannot be successfully remelted, as the grain becomes coarser. They may be worked up with a new batch of soap, however, or can usually be disposed of to laun dries, etc.
The formation of " bags " in `• cold-process" soap, it is said, can be prevented by passing a hand crutch back and forth longitudinally through the framed soap several times. After the soap is cut into cakes it is racked and allowed to form a skin by action of the air. Different soaps will require different lengths of time, and the state of the weather will have considerable to do therewith. If possible, select a clear, dry day for pressing, and avoid a clammy, soggy day, as on such days all soap sweats and becomes frothy in press ing.
To prevent sticking of the soap to the dies, it is necessary to sponge the dies or soap in some liquid in which soap is not readily soluble. The best way is to sponge the cake on both face sides. For sponging, oil of myrbane and oil of citronella, either singly or mixed, have been used. Salt water, however, is better, and weak acetic acid (vinegar) is best.
Fig. 1 represents a machine for making soap by the '• cold process," remelting and crotch ing soap scraps, inciting and mixing rosin, rendering tallow, etc., manufactured by Messrs. H. W. Dopp & Son, of Buffalo, N. Y.
The steam jacket and inner shell are cast in one piece, having a number of stays between the inner and outer shell ; there is a large outlet in the center of the bottom for the dis charge of the contents. A steam-heating radiator, composed of a series of cylindrically arranged pipes having open spaces between them, is placed in the center ; through this radiator swain passes directly to the jacketed part of the kettle, which can be cut off from steam supply so that the inner cylinder only has steam. A conveyor screw is placed in the center of this radiator, which surrounds the screw. As soon as a portion of the soap is melted, the screw is set in motion, thereby lifting the soap up and dumping it over the top of the casing surrounding the screw, when the centrifugal force forces it out of, or through, the open spaces left between the pipes. The large scraps are carried up and are wedged in between the open ports at the upper end of the radiator. The constant motion of the screw shears the pieces off, and thus, in comparatively short time, the largest scraps are completely cut up, and the whole kettleful of soap will be thoroughly melted and crotched ready for framing. The transferring of the soap into a crotcher after remelting the same, is here overcome, and the two operations are finished in one. Moist steam may be passed at will through the soap scraps, etc., to moisten them, if necessary. Cold water may be passed into the jacket and radiator to facilitate the cooling of the soap. The conveyor screw is worked by power forward or backward by shifting the clutch that drives the bevel gearing.