Now here's a new one.
I am doing some opossums, and I had them in the pickle/tan/whatever for oh, about 10 days or so, and in this brew is also some degreaser.
(these are being dressed "preliminary" prior to being dyed and "really re-tanned". This is why it's so inexact. Not recommended for someone looking for a "complete tan" or the inexperienced.)
Over the course of the time period of the soak, the pH has also changed in the soak, from "more acidic" to "less acidic but still acidic". I haven't checked the pH but know things are ok (skins neutralize properly when put in to basic neutralizer).
My guess is that pH was .9-1.0 when started and is now about 4. i.e. going from pickle to tan "naturally" over the course of time.
So, I took some skins out for brightening yesterday, and let a couple of them dry.
Today, I stretched a couple of them once they were about 90% dry, and they have a white, soft, stretchy leather. It stays this way once fully dry, without becoming papery. Even the noses are pretty flexible. The entire skins are affected to a degree, but the best results are found on the belly, chest, legs, tail area, and back.
These skins have not been oiled or tumbled & broken.
Is the natural opossum grease the culprit?
Or should I be asking for those photomicrographs of how the leather fibers align, when exposed to different tans, again.
I'd write it off as a fluke if it hadn't happened approx. 200 times in 1 vat in 10 days. (it's NOT just that pelt!)
Anyone else ever had this happen?
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