I have to say, right from the start, I know nothing about tanning hides. My boys bring skins home from time to time from rabbits, Tahr, deer and wild pigs. We have also had some skins from pigs we raise and even a few from an aborted ostrich venture. We have tried some of the methods such as baking soda and kerosine but that seems to me to be more perserving the hide rather than actually tanning it into leather. We have a Tahr skin on the floor done by the baking soda method but I suspect that if it ever got wet and the baking soda washed out of it, it would rot.
We have a large walnut tree which gives us 4 to 6 20litre buckets of walnuts each year and some 15 small trees that have been planted in various places. One year, we left a bucket of unshucked walnuts outside and it rained that night. When I poured the walnuts out on a flat surface to dry, the water was the colour of very strong tea. Tannin, I thought. Perhaps we can tan hides with that.
This year when we harvested the walnuts we kept the husks which had collected on the net and the husks which we had to peel from some of the shells. This husk is fleshy and green when the walnut is growing but by the time the walnut falls, the husk is black and papery.
At present we are in the middle of tanning a catle beast hide (cow for those of you north of the equator) and I will describe what we have done and what we do in the future as time goes on. No idea how it is going to work out so I'll add information as we go along.
We got the hide from a friend the day it was skinned from the cow. It had lots of fat and some meat on it and hair on the outside. One of my boys and I hung it over the rail of our trailer and started to flense it. I can't say we did a very good job. We got off pretty well all the meat but quite a bit of fat was left and I managed to make a couple of holes through the hide. I need much more practice.
I know Sodium Hydroxide (lye) is supposed to dissolve fat and loosen hair so we put 500g of lye into a bath tub out in a field, with enough water to cover the hide and we pushed the hide around in this solution. We left it there for 4 days, stirring it around a couple of times a day. The initially very flexible hide turned very stiff. After 4 days we turned the hide out on to a piece of ply wood, hair side up and started to scrape off the hair. We used a variety of tools, all dull, including a weeding tool that looks like an eskimo ulu on the end of a rake handle.
Once we had the hair off the hide, we put about 15kg of salt and two feed sacks of walnut husks into the bathtub with enough water to cover the hide. There were also a few handfuls of small walnuts that we hadn't bother to shuck. In went the hide and we stirred it around for a few days. My son decided that this was not a very convenient vessle for the purpose so he removed the top from an oak wine barrel and transferred the whole lot to the barrel. It was indeed much more convenient. Very easy to plunge and stir the whole lot with a stick.
After a few days, the hide started to turn brown with a lovely......well....walnut colour. Within two weeks the penetration was about a fifth of the way in (seen by cutting a sliver of hide off the edge. We decided to try something
On a fairly dry day, we pulled the hide out of the barrel and draped it over the barrel. The idea was to let it dry so that when the hide was put back, it would suck in more of the tannin. We will continue this way for a while, until the hide is brown through. It actually feels a little leather like already (wishful thinking?).
Latest development. My son made up a flensing rig. It is a 200mm diameter turned log of about 2m long with a couple of lets set into one end. The log thus sits with one end on the ground and the other end at about belly button level. He then sharpened a 40cm long mower blade along the edge. The hide is draped over the log, you lean against the upper end of the log and scrape away from yourself with the blade. Seems to work a treat. We are reflensing the cow hide and allowing it to dry somewhat as we do it. Where the leather is thin, it is dark brown all the way through. The rest is dark about a fifth of the way through. Will immerse it again in a couple of days and the dry leather should suck up more of the tanning liquor.