Ok after some experimenting, I have in fact very nicely tanned a rabbit skin using black wattle bark. It is not your thick, puffy professional leather, but it is soft, supple, and leathery, properly tanned right through, has stained the skin a pleasant pale brown (not too dark, a perfectly natural colour), and the fur is unstained.
Below is how I did it: it is a bit long, but it was quite a complicated proccess!!
I got the tannin contents etc from a book, but that was about all, as the main book focused on alum and chrome tanning. The basic method was from the same book, but only used for alum tanning, so was a bit of a punt really. Worked well though.
I used Black Wattle bark for a tannin source, (35-40%) as we have planted shelter belts of it around our paddocks that are now about 5-6 years old. Other barks also have tannin, to varying degrees. I do have a book that list the average tannin content of most common trees in australlia and nz. Pine (13.9%) and Tanekaha (28%) are also common around here.
My recipe is as follows:
500gm dry wattle bark, ground
1 3/4 litre hot (not boiling) water
Steep for about four days. Makes a tannin infusion of about 3% by volume (according to figures from the book). You get about 1 litre out of that, the rest soaks into the bark. Difficult to figure out the tannin percentage there, as the bark percentages are in weight. I had to work off an example in the book.
I first chopped up the wattle bark, and then put it through an old food processor until it was as fine as I could get it, a sort of coarse crumble. Had to sieve it and redo the coarser stuff a couple of times and it made a lot of dust. Might go better ground before drying. I used hot water because it steeps better, but the books all say use warm, not boiling, as the boiling water, while it steeps the tannin better, also steeps out non-tans which can effect the end product.
The skin needs fleshing, all the membrane and tissue removing until only skin is left. You can use the edge of a knife dragged across to aid in this, or get a proper fleshing tool. These are a sort of claw, several square metal teeth, bent slightly backward towards the handle to help them grab onto the membrane. I think those are more a modern idea, as the traditional thing is just a curved knife. They work really well, without it I just couldn't get the stuff off, thus my first few failures. I had not remembered the fleshing tool up the shed at that stage - had been being used to clean up sheep with flystrike for several years - yuck.
(Just a hint, don't leave your rabbit skin wrapped securely in an airtight plastic bag up on top of the anvil out of the way of anything while quickly popping up the shed to get a tool you don't expect to have to spend ten minutes scrubbing. The Feline Brat is smarter than that. Lets just say it was another day before the next skin thawed.)
With rabbit skins it is all a distinct separate layer, and once you get it started it comes off pretty well. The first time I found what I thought was the layer and removed it, but it wasn't the whole lot, just a thin thing over the top, and the waterproof membrane was left so those skins didn't tan (a previous attempt). The layer you're looking for is quite tough, and when it comes off the skin is a very clean colour underneath. I found it was a
lot easier to get off a thawed frozen skin than a fresh one, and don't even try salting them. Resoaking is necessary after salting, not good for the fur, and they still don't flesh very well, not to mention the strange sticky, gummy, greasy bits around the edges that just won't come off.
Then I laid the skin out flat in a tray, flesh side up, and made a "tawing paste" out of my tannin liquor. I had added, once the water cooled, added a spoonful of bleach to the liquid to stop it fermenting, as the last time I did this the paste went a bit yeasty on the skin, and while it didn't seem to make it any worse, it can't help. That was the only chemical I used, and hope to be able to do without that sooner or later. To make the paste I put a spoonful of flour in a bowl, added a palmful or so of salt, and mixed in enough of my wattle bark liquid to make a paste. Not a thick dough type of paste, a pourable paste. Sort of like batter.
Only make as much paste each day as you think you will need. If you have some left over, you can still use it the next day, but its safer to use it fresh each time. Spread enough of this on the skin to cover it, not too thin but don't pile it on either, I used too much last time and while all went well it was pretty wet, and a waste of tannin besides. Only apply to the skin side, and try to avoid getting too much on the fur at the edges. Just a hint I found out the hard way ... avoid getting the fur wet under any circumstances. Wool, cow hair, etc is fine but if you want fluffy rabbit, don't get it wet as it sticks down and I for one can't get it back up as nice. If the skin is from an odiforous sort of animal one obviously has to wash it but I'm not game for that just yet.
Cover the skin with a plastic bag sliced open to stop the paste drying out, or lay two skins together flesh sides in. I prefer the plastic as more reliable - doing it with skins tends to dry out more, and also the skin underneath always gets more tanned. Every day, remove the plastic, scrape off the old paste, and replace with fresh. I tanned it for about 5 days, maybe a little more, by which time the skin had definitely changed colour.
It would take longer for a thicker skin, but then the book only says one or two days, but I wasn't happy with the colour change by then, the stain is supposed to indicate tanning. By the time it was finished, the skin was practically swimming as the salt had attracted a lot of moisture, and the leather when I finished did have a salty smell. As such I think it would be best to stop adding the salt after the first couple of days, it was really only there to stop the skin starting to go off and dropping fur before the tannin did its job.
Once tanned to satisfaction, I scraped of excess paste, and sponged the skin clean with a little water. Then it needs pegging out on a board under moderate tension, not stretched out really tight as it shrinks when drying and may tear, just taught enough to keep its shape and size. You can nail it to a board, or tie it out on a mesh frame, but I used a plastic bread tray and held each point of the skin to one of the holes in the tray with clothes pegs.
Worked quite well as it didn't end up with holes around the edges, and if it got too tight it could pull free rather than tearing. Once it was dry, I laid it out in a warm sunny spot, and went over the fur with a comb and a bristle brush to bring it up and tidy it off. Fur likes being worked warm and goes glossy, thus the sun. If there is any paste left around the edges on the fur at this stage, its is dry and will come off nicely with a little brushing.
After that was the working of the skin to get it soft. That was a learning curve in itself and I'll be able to do it a lot quicker next time.
Basically the skin is constructed of fibers interlaced, and filled in between them is glue (hide glue, obviously). Working the skin does not mean breaking up and bending those fibers, although that would work, it would also make the leather prone to cracking. What you have to do is get the skin to exactly the right moisture content, and work it to break up the glue between the fibers, so when it drys they will flex and slide freely. As such you do not want to work it dry, it has to be the right percent moisture so the glue is soft, and the fibres not too brittle. If it is too wet, it will simply reset as stiff as a board.
The ideal moisture content is techniquely 25-30 percent of the dry weight of the skin substance as water. To work this out, you have to weigh the dry skin. A rabbit skin doesn't weigh much, our scales can't see it, so it helps to have three or four and divide the total amount. Of course if you are weighing something like a sheepskin that has a lot of wool on it, your figures will be drastically different ... you're only looking for the weight of the skin.
In the instance of my rabbit skin, it came out to 15ml water. Or it might have been 20ml, don't remember for sure. I used a spray bottle to apply it evenly to the skin side, folded the rabbit in half flesh side in to keep it damp, (the books say to roll it up, but I figure then half the water will soak into the fur instead), and left it a couple of hours. Then I wandered around the place rolling, pulling, and flexing it for ... well too long anyway.
It became very nice and supple. I became very stiff.
Then when it dried out it went back all stiff and papery.
So next day I tried it again. Same thing. So I looked up the book again. It mentioned lubrication: either sulphated oil of some sort, or less commonly, include egg yolks in the tawing paste. The amount of egg yolk worked out to 5 per sheep. Sqaure acreage wise, my rabbit skin was 1/4 the size of a sheepskin, so I figured one yolk should be about right. So I followed the directions, damped the skin again, mixed the yolk up 50/50 with water to make 30ml, brushed on 1/2, left for 30 minutes, then brushed on the rest and covered with plastic overnight. In the morning it had soaked in rather well, so I removed the excess, wiped clean yet again,
and reworked it.
This time it came up much better, but still not good enough for me ... I was bound and determined to get a soft, luxurious, "professional" leather.
Don't laugh ....;-)
I am still convinced that it should be possible to do it to a satisfactory standard with egg yolk, as it has been known for some people to actually tann with egg yolk (oil tannage), but I need to experiment with it.
So I went through it again. This time I ignored the book (more than before that is), and in the lack of "sulphated" oil, simply mixed up cooking oil (rice bran oil) 50-50 with liquid dish soap. Then I rubbed that well into the skin, don't know how much, just rubbed it well in all over. How to massage a dead rabbit. (macabre sense of humour at work). Rolled up the skin, and left it a couple of hours before working it again.
This time I resolved to do the thing properly (ie traditionally), rather than working between the hands, and in the lack of a real "stake" (post with a rounded top), I pulled it, flesh side down, over the top of a bottle. Kept going, doing little corners at once, in all directions until the whole thing was all nice and soft. Dried it out with great trepidation.
(This being the fourth attempt to soften it, I'm sure you can imagine my bravery at this stage at not just sealing it in a ziptop bag and leaving it damp for all eternity ...)
Phew!! It dried out really nice. Still soft and supple finally, and much to my relief, doesn't apear too greasy either. A quick roll between the hands, and its as soft as you could want it, and no longer papery. Went
over the fur in the sun with the hearthbrush again, as it had got a little roughed up in all that working, and besides there's just something about fur that needs stroking. Trimmed a couple of the rougher edges, but really the edges are pretty good since I didn't nail it, brushed it again (it called), and I have a very nice rabbit skin.
It did have, if you stopped to smell it, a rather noticable skinny, barky, salty smell, which did concern me a little, as in most applications you don't really want a smell to furs, but on leaving it laying around to air for a few weeks the odour has faded to virtually nothing.
The skin is dyed (from the bark) a light brown colour, nowhere near as dark as they say, the fur is unstained, clean and glossy, the leather is soft and supple.
It has lost the original papery thinness, and while the skin has not puffed out to be the thick, suede finnished leather you see on chemically tanned skins, (how they do that with something as thin as a rabbit skin I don't know) it has softened and thickened up quite nicely.
Just as confirmation that it has indeed tanned, when I damped it, it did not, as previous failures have, revert to something resembling raw rabbit skin, it merely becomes like ... well ... damp leather (strangely enough).
Now (once I've done a few more and gotten used to it) I just have to try brain tanning. It's supposed to be the nicest, softest most luxurious tan out, due to the natural oils in the brain. In anticipation of that, I have some bags in the freezer labeled "Stacey's Brains" and have told everyone they are to be kept as "I may need to use them one day - haven't yet but you never know"!!
Just a hint, if you ever do decide to try brain tanning, and are presented with a head to get the brain out of, forget the hammer, head straight for the hacksaw, its the only way to get through.
So there you are, how to tan a rabbit skin using wattle bark, from the quite technical to the fairly random. A book-length essay I suspect. Hopefully that helps.