I have been tanning some sheepskins with Lutan F after pickling them with formic acid.All at different time. Some has turned out good, but some is not good. Most of the skins that are affected, seems nice, but some areas seems to never get really dry: seems fat,and as if it sweats humidit. And some of these areas also slips hair, though not all.
Can it be concentrations of salt? Or is it the formic acid or the tanning chemicals that is uneven taken up by the skin?
Some of these tanningprocedures has been outside, in low temperatures. Maybe that has something to say? And, some of the skins were washed with detergents that I didnt gat totally out of the skins, so it raised the pH in the picklesolution. As a response to that I put much more formic acid as supposed in the original receipt.
A lot of questions, but maybe some has some has similar experiences and have some answers..?
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Cold can effect Ph levels of your pickle. Where they fleshed down enough?
If the finished skins sweat or weep - then the problem is excessive salt left in the skin. Normally its removed during neutralization and tanning - but its also a good idea to rinse the skins when you remove them from the tan. Not wash - simply rinse with water! Then drain and oil them.
Persistent low temperatures (below 12 degrees C) can solidify the fats present in the skin and cause formation of spew on the leather surface. Your problem isnt salt, its the cold.
The fats are solidifying and rendering your degreaser ineffective, and also not allowing the salt to do its job, causing slippage in those areas.
Thanks a lot for the answers! I had in my backhead that it could possibly be related with the low temperatures.But, can I do something with the affected areas (that didnt slip) now?