Yes I have. It is another version of "mild, can you call it tanned" vegetable tan, but I've done sheep and rabbit skins and it is very satisfactory for indoor use, or car use, etc. I have one on a saddle that is doing well too. Lasts well, 5 years so far. However for you project I would definitely soak it in a more traditional way.
Your Sumac has useable leaves. Better than any other thing you have in fact. They are 21-32% tannin by dry weight, depending on what type you have. That is better than the bark, and significantly better than oak bark. To calculate the % of your finished solution, work it out by that, but allow an extra 50% because not all the tannin will leach out.
I use a "paste tannage", I think I'm the only one who does with a vege tan, I don't want colour or tan on the fur and could think of no good reason why not to try it.
For a pig skin you'll definitely want to submerge it though. It is so thick. I would suggest soaking it in a 1% tannin solution for the first couple of weeks, followed by a 2% for another couple, then a 3% until it is finished. If you start too strong with a thick skin the tannin seals the surface and it will hardly penetrate.
Add 50g salt to every litre of tanning liquid.
Check if it is done by making a small cut near the neck or other thick part, the colour should go right through.
If you mean Outer soles for shoes, then I would agree not to work (break) it. If you have a hard leather it might be nice to finish it with a oil and beeswax polish over that too. If you plan on carving grip patterns in the leather, I would use the polish after that. Apart from a nice appearance this will protect your leather. If they are to be outdoor shoes, make sure they are cleaned and dried properly when they get wet, and at regular intervals, or after serious wettings or muddings, re-oil and polish.
Hopefully treated this way they will last for a long time, even if your tan isn't up to ancient standards (which would try anyone's patience, I like to finish projects within 2 years)
Good luck with your hide!
My recipe for a rabbit skin is as follows:
500gm dry wattle bark, ground
1 3/4 litre hot (not boiling) water
Chop up the wattle bark, and then put it through an old food processor until a sort of coarse crumble.
Add hot water, and steep for at least 4 days. If it will be stored for longer, add a dash of chlorine bleach to the liquid to stop it fermenting.
This theoretically makes a 3% tannin solution.
The skin needs fleshing, all the membrane and tissue removing thoroughly. If not done properly, vegetable tan just won't penetrate.
Then I laid the skin out flat in a tray, flesh side up, and made a "tawing paste" out of some of my tannin liquor. add enough flour to make a thin batter, a little bleach, and a fistful of salt. The bleach is to stop it going 'yeasty' on the skin. It doesn't reduce the colour though, in fact it makes it darker!
After the first 2 days you can stop adding the salt, or it will attract too much moisture.
Spread enough of this on the skin to cover it, not too thin but don't pile it on either. Only apply to the skin side, and try to avoid getting too much on the fur at the edges. 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 fix it.
Cover the skin with a plastic bag sliced open to stop the paste drying out. Every day, remove the plastic, scrape off the old paste, and replace with fresh.
Rabbit skins 5-7 days, sheep 10-14. Very short for vege tan yes, but it worked!
Scrape off excess paste, and sponge the skin clean with a little water. Peg out on a board under moderate tension. Use clothes pegs on a mesh board ... this way if the skin shrinks a lot it will pull free rather than tearing holes in itself.
Once dry, lay it out in a warm sunny spot, and go 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, it is dry and will come off nicely with a little brushing.
Working the skin is one of the most important steps. Skin is a lattice of fibers surrounded by glue: if allowed to dry naturally, it will set hard and stiff.
The trick is to flex and work it thoroughly at the right level of moisture to loosen that glue, so when it dries the fibers will move freely. Too wet, it will still set, too dry, you will break the fibers and your leather won't last. 25-30% moisture is about right.
Redamp the flesh side with the correct amount of water, fold flesh to flesh, and wrap in plastic. Leave for 8-12 hours.
Rabbit skins need about it came out to 15 -20ml water. Then I work every inch of the skin thoroughly, first just rolling it between my hands, then working it over chair backs, bottle necks, anything that will give the leather a really good flexing. This takes the time and effort. As you go, the skin will get more flexible, and you will get more stiff. Some native peoples chew them. I'm sure they have the best leather, but personally I don't like the taste (I had to try for science sake).
Many skins (rabbit skins do) need oiling as well. You know this because when you finish working and dry it it turns hard or papery again. (Your language may deteriorate rapidly at that point). When I have a skin that needs this, I use a 50/50 mix of vege oil and liquid soap, you can add some egg yolk to this as well for a smooth creamy mix (just oil will not do), and paint on a little at a time partway through the working process, working it in as I go.
Some skins may be very greasy already, and adding oil will make them very oily, so check first.
Now dry your skin out held flat again, then give it a quick roll between your hands to soften. Tidy up the edges, trim off any messy bits, brush up the fur side again.
The nature of the product in my experience is as follows:
It is medium brown right through the skin, but not the fur or wool. It is soft and flexible, not as soft and puffy as commercial leather, but satisfactory for most purposes. When damped, it resembles damp leather. (My previous failed experiments have returned to raw skin appearance when damped).
It does have initially a rather noticeable skinny, barky, salty smell, but leave it laying around to air for a few weeks that fades to virtually nothing.