Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 184

Glue, size, and gelatine are varieties of the same substance; they differ only in the quantity of moisture and of impurities which they contain. Glue contains so many impurities that it is unsuited for use other than as an adhesive for wood, paper, etc. Gelatine-yielding substances are legion, those in commercial use including the skins of all animals, tendons, intestines, bladders, bones, hoofs, and horns. In the preparation of ordinary glue, great use is made of the parings and cuttings of hides from tan-yards; tanned leather is useless for the purpose. Briefly, the process consists in boiling the animal matter and straining the product into coolers, where it thickens into a jelly. This is cut into sheets of suitable thickness and dried in the open air on frames of wire netting. Spring and autumn are the most suitable times for drying the glue, the frost of winter and the dry heat of summer having injurious effects. The size is not dried, but is sold just as it is cut from the coolers.