Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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galls

The dried excrescences from certain trees and shrubs, especially Oak galls (Quercus infectoria), from the Near East and Eastern Europe; Chinese galls (Rhus semialata), from the Far East; Tamarisk galls, from several species of Tamarix, located from Morocco to India; and Pistacia galls, from several European and Indian species of Pistacia. All are relatively rich in tannin (36 to 60%) and are said to contain free gallic acid in addition to tannin, as well as an easily soluble form of ellagic acid. In general, the tannin is not homogeneous and is believed to be built up as a polygallol-ellagic acid.

The galls result from the plants reaction to irritation caused by the larvae of various insects which lay eggs in the cambium area of the plants.

Although galls were used extensively over a period of centuries in the manufacture of certain inks, and in the tanning of leather, they are little used today for tanning outside of the areas where they are collected, largely because of the expense involved in their collection. See also: IRON-GALL INK ; VEGETABLE TANNINS . (175 , 235 , 363 )




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