Freeze drying, or just putting hides in a freezer, is a really helpful way to get hides soft. Really seems to open up the hide. Ageing freeze dried hides (or just dried hides) supposedly makes really soft hides as well. I wonder if the bacteria on everything find the hides and slowly break down the gunk in the hides (aka ground substance) with enzymes (proteolytic enzymes) that people usually use basic soaks (lye and/or lime) and bating (pigeon shit and urine). I have one freeze dried hide that I’m going to experiment with.
I wrote the following in the Alaska gear thread about urine tanning:
"I don’t know how the Yup’ik tanned their salmon. My guess is they used urine. I don’t know how to urine tan. There are instructions on the web, but because I haven’t done it before I can’t recommend they will work. Urea forms ammonia and that creates a basic environment (12 pH) that likely breaks down fats and kills bacteria. But I don’t know how that makes it waterproof. Sounds like alum tawing, which is not water proof. Maybe the added fats make it water proof? This is also known as “oil tanning” which I don’t fully understand yet. Braintanning is basically oil tanning with the added step of smoking.
I imagine that you could urine bate (tanning term for getting shit out of the hides that will make it rot), wash repeatedly to get to a neutral pH, dry a little, rough up the membrane side, put in warm emulsified oil/water, wring out and stretch until dry, and smoke. I would maybe even consider bating in urine and salt water, kind of a bate/pickle to preserve the hide through the tanning process.
The best source for this stuff is likely Lotta Rahme’s book Fish Leather: Tanning and Sewing."
