Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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salt stains

Discolorations which appear on the grain surface of hides and skins that have been cured by wet-salting. The stains, which are usually greenish-blue or rusty-brown in color, may develop in the corium of the skin, in which case they are usually flat, oriented parallel to the skin surface, and surrounded on all sides by normal hide fibers. They may also develop on the flesh side, or on the grain surface of the skin. All three types are characterized by a hardening of the fibers caused by a grainy deposit which can be removed by treatment with strong acid solutions. As bacteria are found only in the stains which form on the flesh or grain surfaces and not in the corium, it is not believed that they are caused by these organisms, but by deposits formed from alkaline earth salts present in the salt and autolytic decomposition products of blood and non-collagenous hide proteins. Their presence reduces the value of the finished leather significantly; however, the addition of 3% soda ash and 1% naphthalene by weight of the salt virtually eliminates the problem. (248 , 363 )

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