I was reading about different tanning methods and I'm fairly confused about what they're achieving.
Like, some cultures would soak hides in poop... for proteolytic enzymes? And others just wouldn't and that seemed to work fine. Or you can use chromium III sulfate to change the spacing between collagen threads, but also you can just cover the thing in astringent bark water (or other sources of tannic acid, but why would you gather small rare parasitic oak galls if you could just use waste tree bark or leaves), and wouldn't it be nice if your nice-smelling leather products that children might want to chew on weren't impregnated with poisonous heavy metals?
Or I saw a buckskin recipe that covered the hide in egg wash, or a mix of grated bar soap and vegetable oil, or you can rub the deer's brain on its skin, and supposedly these methods all soften the leather in equivalent ways, with emulsions of triglycerides in water, but they don't even mention a protein changing step to finish. It's just: 1) take off the fur and fat with alkali and then 2) soften with brain grease or eggs.
And then I see references to "tawing", meaning treating the hide with alum and something else, like eggs or flour, as an alternative to proteolytic enzymes or protein-complexing chromium or protein-binding tannins, so maybe the alum does something like tanning but you need to soften the hide at the same time to prevent the alum from over-drying the hide?
It feels like there are 20 different ways to make leather, so it shouldn't be a finicky process, but all of the processes require some highly specific bullshit like green papaya latex or deer brains or fermented pigeon droppings.
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