Cheers on the info of weights of tanning material to skin – useful numbers to have.
I was a bit mental learning to do this, having brain tanned a rabbit, i then went and vege tanned a sheep skin (minus the wool) – it was a pig to do, a great learning experience, and i got useable leather out of it!
Re: brain tanning, Yep – “each animal was given just enough brains to tan it’s own hide” i believe the saying goes. For those that are squeamish, egg yolks can be used, Ive even heard of a version that use homemade lye soap and neat’s foot oil. Basically, any emulsion of fat and water will do the trick.
Top tan bark trees: Oak sp., acacia sp., camellia sp. (they are what is used to make tea! – think of the black tanning inside a metal teapot!) Birch, alder, fir, Sumac, chestnut.
There are actually two kinds of tannin which impart slightly different properties to the finished leather. This guy explains it better than i do