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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