Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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quebracho

A South American tree, genus Schinopsis , the wood of which is relatively rich in tannin. The name "quebracho" (pronounced "kay-brat-sho") derives from a contraction of the colloquial Spanish or Portuguese term "quiebra-hacha" (ax breaker), and refers to the extreme hardness of the wood (specific gravity 1.12 to 1.39). The trees exploited for tannin include Schinopsis balansae (quebracho colorado chaquerno) and S. lorentzii (quebracho colorado santiagueno).

The heartwood of S. balansaei averages 20 to 25% tannin, while that of S. lorentzii averages 16 to 17%. Untreated quebracho tannin is relatively insoluble in cold water and is usually sulfited to overcome this disadvantage. The untreated tannin also has a high pH value and low salts and acids content, while the sulfited product is the same except that the salts content is high. Quebracho belongs to the condensed class of tannins.

Quebracho tans very rapidly, converting hide substance into leather in about one-third the time required by a tannin such as oak bark. Used alone, however, it produces a leather that is light, lacking in firmness, and with poor resistance to wear; therefore, it is commonly mixed with other tannins, such as hemlock, mangrove, oak bark, myrabolans, and sumac.

Quebracho has been used extensively in the tanning of leather since it was first introduced over one hundred years ago. It has been used so extensively, in fact, that its use has declined sharply in recent years largely because of over-exploitation. (175 , 306 , 363 )




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