Glue, an impure gelatine. It is prepared from the clippings of hide, hoofs, and horns. These are steeped for several days in lime-water, to remove the hair and blood, and then drained and dried in a current of air for some days, that the lime may absorb carbonic acid, and thus prevent the injurious effects of the alkali upon the gelatine. They are then boiled in water until the solution is found to gelatinize firmly on cooling. The impurities are allowed to settle, after which it is allowed to gelatinize in shallow wooden boxes, cut into slices, and dried upon nets. Good glue is semi-transparent, and free from spots and clouds. When wanted for use, it is broken in pieces and steeped in cold water until it softens and swells. It is then melted over a gentle fire, or what is better, in a water bath, and applied in a liquid state with a brush. As the stiffening of glue depends on the evaporation of its superfluous moisture, it will not harden in a freezing temperature. Marine glue is a composition used for cementing materials that are exposed to moisture. It is made by dissolving 1 part of india-rubber in 12 parts of mineral naphtha, and adding 20 parts of powdered shellac. It not only resists wet, but cements glass and metals as well as wood. White fish glue, or diamond cement, is made of isinglass dissolved in alcohol.

Entry from Everybody's Cyclopedia, 1912.