Raw hide and skin damage caused by preservation

Salted raw stock
1. Lead stains
Lead compound are contained as denaturing agents in curing salts, used mostly in overseas countries. They produce similar stains as iron.
2. Iron stains

Contact of the hides with iron parts or rusty iron compounds. They produce brownish stains which are further intensified by liming chemicals or tanning agents containing phenol. In many cases it is possible to eliminate them by a treatment with complexing agents.
3. Rottenness
If curing is inadequate or is performed too late and if the hides are stored too long at excessive temperatures in the salt, an increased development of microorganisms occurs on the skin. It starts with slimy smears on the surface, followed by hair-slippiness and at an advanced stage a loosening of the grain layer in some sections and destruction of the skin by the formation of holes.
4. Flesh side discoloration
Noticeable through red, blue or violet discoloration on the flesh side. These stains are caused by color-forming bacteria which result in matt to rough grains and hair-slip, and also attack the hide substance. Can be avoided by increased addition of soda and addition of naphthalene to the curing salt.
5. Copper stains
Brown stains caused by copper compounds or copper-containing colors used for making.
6. Naphthalene stains
Brown to red discoloration due to the use of unpurified phenolic naphthalene in the curing salt or by sprinkling the wool of dried sheep skins to protect it against ravage by insects.
7. Mould stains
May occur in all types curing. The stains or coating of different colors( green , red, brown, yellow, orange, white, black) occur in patches or over large areas, depending on the type of mould spore infestation. In the case of prolonged infestation the mould stains will also be visible in the leather.
Prevention is possible by using disinfectants during curing. Mould which has already been produced can be removed to a large extent by brushing or washing.