I’ve mentioned “tawing” and “alum” here a few times, and it occurred to me that it might be helpful if I explain what the hell I’m talking about.
Alum is a naturally occurring mineral, a salt of aluminum. Specifically, it’s aluminum sulfate. Alum is not chrome or chromium! A Google search will tell you that alum is used for pickling and food preservation, as well as making leather. Historically it was also used to leaven bread.
When alum is used for leather-making, the process is called tawing. This is mineral tanning, which is one of the most ancient forms of tanning. Purists will probably argue that it’s “not really tanning” – I don’t totally disagree, but would point out that’s why the process has a different name.
I was taught about using alum on fur-on animal skins by the leather-maker at Colonial Williamsburg, who was a friend of my husband, in 2010.
I’ve heard it said that tawing produces stiff, hard leather. This is only true if you don’t work and stretch the hide as it dries, which is true of tanning with soap, bark, oil, egg, or brain as well!
When I do large hides (sheep, goat, or deer vs. rabbit or raccoon) I first taw the skin in alum and salt. Then after rinsing with clean water, I apply my soap and oil solution to the wet skin to tan it. I realize this sounds like overkill or a double process, but once I started tawing before tanning I never had the dreaded hair, fur, or wool slippage again!
For small pelts I’ll often just taw them by soaking in a strong pickling solution of alum and salt, and then hand-stretching as they dry. It’s so easy to do lots of small skins this way, and the leather can be further softened and darkened with neatsfoot oil.
I’ll do more of these “resource” posts as I go.