The best quality of glue is obtained from fresh bones, freed from fat by previous boiling, the clippings and parings of ox hides, the older skins being preferred; but large quantities are also get from the skins of sheep, calves, cows, hares, dogs, cats, etc., from the refuse of tanneries and tanning works, from old gloves, from sinews, tendons and other offal of animal origin.

By a process of cleaning and boiling the albuminoid elements of the animal matter are changed into gelatine. This, in a soft, jelly-like state, constitutes "size;" dried into hard, brittle, glassy cakes, which, before use, must be melted in hot water, it forms the well-known glue of the joiner, etc.

When a solution is mixed with acetic or nitric acid it remains liquid, but still retains its power of cementing; in this state it is called liquid glue.

Marine glue is a cement made by dissolving India rubber in oil of turpentine or coal-naphtha, to which an equal quantity of shellac is added.