GLUE

is obtained from the hides and hoofs of oxen and a great variety of other animal refuse. The raw material is first steeped for fourteen or fifteen days in milk of lime, then drained and dried by exposure to the air. This constitutes what is called the “cleansing” or “preparation”; and, after being so treated, the “glue stock,” as it is called, may be kept for a long time and transported to any distance without suffering decomposition. Before conversion into glue, the “stock” is generally again steeped in weak milk of lime, and then well washed and exposed to the air for twenty-four to thirty hours. It goes next to copper boilers, two-thirds full of water and fitted with perforated false bottoms to prevent burning, each boiler being filled and piled up with it. Heat is then applied and the whole is gently boiled or simmered until the liquor on cooling shows firm, gelatinous consistence. The clear portion is next run off, a very small quantity of di olved alum being added, into another ve el, where it is kept hot by a water bath, and allowed to remain for some hours to deposit its impurities, then being pa ed into the “congealing boxes” and allowed to cool. The next morning, the cold gelatinous ma es are turned out upon wet boards and cut horizontally into thin cakes with a stretched piece of bra wire, and then into smaller cakes with a moistened flat knife. These small cakes are placed on nettings to dry and are later dipped one by one into hot water and slightly rubbed with a brush wetted with boiling water, to give them a glo . Finally comes a stove-drying proce and the glue is ready for market. As soon as the liquor of the first boiling has drained off, the undi olved portion of the skins, etc., left in the copper is treated with fresh water, and the whole operation is repeated again and again as long as any gelatinous matter can be extracted— the product grading as second and lower qualities. Fish glue is made from fish-sounds and other parts of fish membrane. Liquid glue is made by di olving dry glue and adding nitric acid in the proportion of one ounce to a pound, or by adding to it three times its weight of strong vinegar. Light, clear glues are considered the best and are always preferred, irrespective of strength, for special purposes such as joining light woods, etc., where transparency is of paramount importance, but the only certain means of ascertaining the comparative strength of glue of any color is by a practical test. [s. 276]