Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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Eucalyptus

A tree of the genus Eucalyptus, which has some 600 or more species, including many with bark rich in tannin. It is believed that only in Australia (to which the trees are indigenous) has the bark been exploited on a large scale, and then entirely from trees growing in the wild.

One particular bark, called Mallet (maletto) bark, obtained from Eucalyptus astringens, is actually one of the world's richest tannin-containing barks, having a tannin content that is often well over 40%, and even as high as 52 to 55. Another tree, mugga, or red ironbark (E. sideroxylon), which is also grown commercially in Morocco, has bark containing 30 to as much as 45% tannin.

While the tanning properties of eucalyptus are good, the tannin tends to produce leather that is too darkish red in color. In addition, Mallet bark is low in soluble non-tans (8%) and therefore must be mixed with other tannins or acids to induce swelling or good plumping; mugga tannin fixes slowly giving a leather that is too soft and also dark red in color. See also: VEGETABLE TANNINS . (175 )




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