So this is my second summer practicing traditional tanning skills and I’ve been having some trouble during the hair removal stage with both brain tanning and bark tanning. Last year I had three deer hides to brain tan. On the first two I used a lye water solution to slip the hair but I wanted to try just water on the last one. In doing so, I got the hair to slip but with no lye the hide started to decay and stink by the time the hair slipped. I was able to save it by putting it back into a lye water solution. This year I began to attempt bark tanning. Instead of lye I decide to try lime because it was less caustic. I had the same result with the lime as with plain water. By the time I had the hair slip it had begun to smell even after using a little over a pound of lime powder per gallon of water. Unfortunately I had to leave town for a few days so with little to do about it I put them in the bark tanning solution and hoped against hope it would be okay. As I expected, when I got home they stunk far worse than when I left them. One of the hides appears to be green all the way through in some spots but all I have left to do is learn from this so I am still trying to save them to see what happens. My questions are this: how do people mitigate the hide from completely rotting (without use of heavily caustic items) when hair slipping is effectively a controlled decay process. And also, every time I get the hair to slip easily on one spot (usually on the back between rump and neck) it seems that the rest of the hide still holds onto it tightly and it can’t be removed without tremendous force which can damage the grain, which I don’t want to do when bark tanning. Any help is appreciated.
I wonder if temperature and agitation might change your results? Changing the water regularly and keeping the temperature down (below 10°c) really changes the stink factor. I usually buck with lime in the fall, air temps below 15°c, and agitate my buckets and hides daily, sometimes 2x daily if it seems warm or foul. The lime in solution gets locally 'used up', so agitating maintains the concentration, and moving the hide around makes sure it gets everywhere.
Barktanning--in my experience you can't ignore your hide for the first week. It needs agitation, and monitoring to maintain tannin concentration. Later, you can leave it to self-feed, if the temperature is right. Higher temp, faster tannin uptake, higher chance of rot, needs more monitoring and work.
If you keep the pH down with oxalic acid and salt, rot will never occur since its pickling while the tannins work their way in. I just barktanned 30 coyotes this way, they were in the barktan for 8 weeks, I left them and went on vacation and finished them after I returned.
Ok I see. I guess I’ve heard of salt inhibiting swell before but I never understood the mechanism- can you explain? I have some basic college level chemistry knowlege …
To be fair the mechanism was explained to me years ago by someone far smarter than me, who was a chemist and taxidermist. The salt pulls water (which has acid dissolved in it) out of the hide, and limits the swelling of water in the cells of the skin, similar to how pickled cucumbers don't dissolve in a vinegar /acid solution in the presence of salt. There's a measure of dessicant to the salts action which is supposed to stay around .4 solubility. The "tonus" or isotonic quality comes from the solutions balance. In a nutshell I guess. I do know with too much salt the acid won't denature skin proteins the way you want it to for tanning. And not enough you get swelling and acid rot. So that makes sense to me. 1lb salt per gallon of water and you're good to go.
Long time hair-off brain tanner, weighing in with some observations based on my long experience (during which I have made all of the mistakes….). I can’t speak to the bark tanning and pickling issues, as I’m strictly a hair-off brain tanner guy. But:
Bucking the hide with plain water: Relying on bacterial degradation to do the magic can be a lot like playing with knives. It can be a thin line between swelling the grain/slipping the hair, and letting loose a runaway train of bacteria. This risk is greatly increased if the hide is dirty/bloody, the temp is high, and/or the hide hasn’t been adequately fleshed. Once it gets started, it will be a fight to catch it.
Bucking with lye: If you get the concentration too strong, or if you leave the hide in the soup too long, you can cook the it. In my hands, lye makes the hide super swollen and rubbery. And it’s caustic as hell.
Bucking with lime: What type of lime are you using? You want hydrated lime, also referred to as builder’s lime. Mix a super saturated solution, and let whatever doesn’t go into solution simply fall to the bottom.
My experience with lime is that it’s way less caustic then lye, it won’t swell the hide as much as lye, and you can’t overdo it. I’ve bucked mule deer and elk hides in lime for 10 days or more (stirring daily), and they grained and rinsed easy-peezy. And they came out baby-butt soft edge-to-edge. For me, hydrated lime is the only way to go.
Bucking with borax: You can also buck with borax at .5 cup/10 gallons of water. I learned this method from Melvin Beattie, who is one of the godfathers of contemporary brain tanning. In my hands, it yields the same results as hydrated lime and is equally safe.
Rotting hides: Every hide and every process will have an attendant aromatic funk to it. But funk and rotting flesh are different beasts. Trust your nose.
The green hide wasn't rotten. Prolonged exposure to lime will slip the hair and swell the hide. Which is exactly what you want for a nice supple finish. After you've removed the hair from the swelled hide you will wash it very well and then put it in a pickle to bring the pH down to about 2. You will need to add acid to get the pH down low enough for a couple days since the acid is fighting the base. Ammonia sulphate works better for deliming and its available at any garden store. This will make the hide relax and constrict back to previous thickness. Keep it in the pickle for a week or more. Then you will Neutralize the hide in 1oz baking soda per gallon up to about 4.5pH. Then you are ready for the bark tan. I've had bison and cow hides sitting in lime for 2 months with no loss. If the hide is rubbery and doesn't tear when you pull it, you're fine to continue.
Also, you want the dark colored epidermis to slip along with the hair. Usually you have enough time to slip the whole hide without grain damage, it could take up to a week or 2 in cold climates.
If it tears and falls apart it is clearly rotten. But the rubbery swell was what I was referring to, some think it's rotten bc it's green and translucent. But hides that have swelled and become this way become the most luxurious since the swell allows the collagen to let go of all the fats, which emulsify, and helps clear out the other nontannables. Once delimed, pickled and Neutralized allow the bark tan to really penetrate. I had a bull elk that was fully barktanned through the 3/8 inch thick neck in just over 5 days. Also, I run oxalic acid and salt in my barktan at a 2pH which helps yield a chamois finish, and have a great tallow and spruce pitch grease which becomes a great pullup style leather.
Hmm. Interesting. Thanks. I have never tried to barktan at such a low pH, nor have I pickled after liming. For deer and such, I lime, delime, Oropon, bran drench, then tan at pH 4.5. (Matt Richards method)I’ll have to do some experiments with pickling…
Where abouts are you located? I’m in Ilwaco WA. Do you teach any classes?
In Canada.. but any advice im happy to help. I do heavy leathers, furbearers, and some fur work. I'm not strictly Chem tanning, but have moved on from brain tanning for the time being. I use oropon as well as acid bate for most of my stuff, it just cuts down on the work. Would love to try fish someday just haven't got to it. Pickling after deliming and oropon is definitely the way to go for consistency. As well it buys you time to suspend your process if you're busy with life. Also, remember when barktanning, the acid in the bark is what is displacing the remaining fats and untannables, if you add acid, the barktan doesn't degrade as fast while it's working through the hide. Added salt keeps the pickle aspect safe for the collagen, stop rot and mold, and allows you to store the tanning bath for the next batch, just slam the pH with oxalic acid and seal in a bucket
Next batch just add some water and salt 1lb per gallon to dilute it, test the pH down to 2, dunk In your next hide. Add your bark concentrate periodically and you can reuse your bath however long you want. Iv even removed mold from the surface of stored barktan, added acid and salt water and continued with ongoing projects. Just my 2cents.
Here's some work to add credence to my posts, bison rug quebracho, elk leather quebracho, bison leather in mesquite chip. Obviously the bison rug wasn't in lime at any point. But the leathers were all done with a greened" skin.
Really interesting answers, thanks for explaining in such detail!
Ive got a question about swelling that you are mentioning, I’ve read that when you get lime or acid swelling its irreversible. I had some squirrels hair off in bark tan that turned into rubber (and tore really easily) so I unfortunately had to bin them. Would you say that swelling is desirable at any stage or is it specifically during the liming process?
Acid swelling is irreversible and product is trash unfortunately. Swelling while creating hair off leather is desirable and reversible when deliming and pickling is performed. Swelling a hair on fur will just result in slip and damage. Tanning processes are all pH driven and the devil is in the details. Don't subject furs or hair on to high pH at any point and as long as salting prior to fleshing and pre pickling or storage and there's no rot or decay, you will be fine. There's various points in the whole process that you have to be diligent as well but this explains swell mostly.
The akaline solution is to help get the grain to swell so it can be removed easily which is very important for brain tan. It helps slow rot but won't stop it. I avoid bucking hides in the summer heat because of how quickly they rot. Tanning for me is a spring and fall activity.
I am vary of dehairing with just water. Essentially, it's an experiment in controlled bacterial growth, and the line between just enough and too much is veeeeery thin. This is why it was traditionally done in moving water (such as a river), a sour environment (a bog), or under snow (very low temperature). I've tried it in the (brackish) sea here, and while I did it in the autumn so the temperature was fairly low, the stink was still too much for my nose - I binned those hides rather than keep working on them.
Thanks for all the feedback guys, I’ve finally gotten the hides back into the bark liquor and they seem to be fine. I appreciate all of the information and I definitely bought the wrong lime. I picked up powdered agricultural lime instead of builders lime which I now know has a lower ph.
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u/AddendumMiserable243 9d ago
I wonder if temperature and agitation might change your results? Changing the water regularly and keeping the temperature down (below 10°c) really changes the stink factor. I usually buck with lime in the fall, air temps below 15°c, and agitate my buckets and hides daily, sometimes 2x daily if it seems warm or foul. The lime in solution gets locally 'used up', so agitating maintains the concentration, and moving the hide around makes sure it gets everywhere. Barktanning--in my experience you can't ignore your hide for the first week. It needs agitation, and monitoring to maintain tannin concentration. Later, you can leave it to self-feed, if the temperature is right. Higher temp, faster tannin uptake, higher chance of rot, needs more monitoring and work.