This arrangement can only be recommended for establishments where but one variety of glue is produced, and the different layers in the clarifying vat are not separated according to their clearness. Before running the liquor into the boxes the latter should be moistened with water, or, if made of wood, coated with oil, stearine, or paraffin to prevent the liquor from penetrating the wood and the solidifying glue from adhering to the sides.
After the solidification of the glue, which generally takes place in twelve to eighteen hours, the boxes are inverted upon a table with a smooth top of wood or stone previously wetted, so as to prevent the adherence of the gelatinous cake to its surface. To detach it from the sides of the boxes the moistened blade of a large knife is generally used.
Cutting the cubes of glue into commercial cakes or sheets is readily accomplished by observing the following instructions:—
The shape of the cakes depends principally on custom. The consumer is used to a certain variety of glue, and if it is not offered to him in the customary shape, he might refuse it and take his custom elsewhere. The quality of the glue is the next point to be considered. If very dark, it is advisable to cut the glue into thin cakes, and if turbid, into thick ones, in order to make this defect the less apparent. Thicker cakes can also be cut if the conditions for drying them are favorable, and thinner ones if the reverse is the case.
The mass is first divided by a steel or brass wire stretched over a frame, like a bow saw, into horizontal layers. The size of these layers is regulated by guides which are placed at distances corresponding with the desired thickness of the cake of glue. Instead of one wire, as many as the cakes of glue to be cut, can be stretched over the frame, which is best made of iron and provided with conical pins by means of which the wires can be tightened, in the same manner as piano strings, when they have become slack by use.
The width and thickness of the cakes of glue are regulated by the distance of the wires from each other, and the length by the width of the box. The cakes thus formed are dexterously lifted from the block with the moist blade of a large knife and placed upon nets.
Instead of using wooden or sheet-iron cooling-boxes, it is recommended to pour a layer of liquor of the desired thickness of the glue cakes upon large polished stone slabs, and when congealed, cut it into sheets, which are placed upon the nets to dry. The advantages of this method are obvious. The liquor cools more quickly by being exposed in a thin layer upon a large surface, which reduces the danger of spoiling, and a strong evaporation of water and consequent concentration take place. Besides, the cakes show the smooth surface of the polished stone, and become in a short time so hard, that when placed upon the nets, the twine will make no impression upon them.
Liquors which in gelatinizing do not become very solid, are not run into forming boxes, but upon glass or zinc plates, and thus spread out in a thin layer, acquire sufficient solidity to be removed cake by cake after being cut. The plates upon which the glue is run are placed in frames and laid upon a table furnished with a rim about 1 inch deep. To accelerate gelatinization of the liquor, the table is flooded with water before placing the plates upon it.
Where cooling-boxes are used, the jelly when completely congealed is placed upon a table with a stone plate, by inverting the boxes, and then cut into cakes. Figs. 15 and 16 represent the tools for cutting the jelly into cakes. The block of glue is laid upon the surface A, Fig. 15, and the frame, B, is gently drawn along in the grooves, a. In the upright portion of the frame are fixed wires at such a distance from each other as required for the thickness of the cakes to be cut.
Fig. 15.