Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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ring color test

A test designed to determine the presence of different tanning agents used in the manufacture of leather. Concentrated sulfuric acid is added to a small quantity of the test solution of ground leather fibers mixed with water. A dark red ring will form at the juncture of the two liquids in the case of a condensed tannin, while a pyrogallol tannin gives a yellow or brown ring. (291 )

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