Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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resin

Any of various hard, brittle, solid, or semi-solid amorphous, organic, fusible substances that are insoluble in water but soluble in organic solvents, and which are classified as natural or synthetic. Resins contain a high proportion of carbon but little oxygen, and have an indefinite and often high molecular weight. The natural resins are excretion or exudation products principally of plant origin (a notable exception being shellac), fusible, usually yellowish to dark brown in color, and transparent to translucent. "Recent resins" are those obtained from living plants, while those dug from the earth where they were deposited, are known as "fossil resins."

Chemically, resins consist of complex mixtures of organic (resin) acids and alcohols, which are generally aromatic in nature, and inert substances (known as resenes), together with extraneous fatty, mineral, or other materials. Gum resins contain carbohydrate gums, while oleoresins are mixtures of resins and volatile oils. The non-volatile residue of conifer resins is called ROSIN , which is the most important resin used in the manufacture of paper. Other more-or-less familiar resins include copal and dammar, which are natural resins used in the manufacture of varnish, accroides, amber, elemi, ester gum, manila copal, mastic, sandarac, and shellac. See also: SYNTHETIC RESINS .

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