I have an old hide I am going to try and mount . I know threr wont be much strecth, I heard I could add baking soda to the soak and that would help. Is this true or is there something else I could do? Thanks Bill
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be real carefull adding the baking soda to a rehydrating solution!
Go to the search button and type in rehydrating. Old skins are very suseptable to acid swell and sodium bicarbonate will only add to any problems you may encounter with rehydrating an old skin.
add 20 mule team borax to nuetralize acid
Please excuse the redundancy, I've archieved the greater part of the below in the past.
The odds of acid swell in an 8 year old tan are very, very, very slim. In order for it to have acid swell at that age, it would have had to have been pickled with an acid that can take it's own salt, and that would have to be in abundance. An example would be oxalic acid. Even then, oxalic that made it past neutralizing is on the deliquescent/hygroscopic side, meaning it will draw atmospheric moisture, taking an active liquid acid form. In which case it would probably be called victim of acid rot at this point in time, and have disintegrated leather fibers to a greater or lesser degree.
On the other side of the scale, if it were pickled with formic acid, you will find that the proteins that make up the "leather fibers" have been disassociated, and have "reformed" as a different structure. "Ideally" the "tanning agents" would now be holding these new fiber structures together. Formic acid is an evaporative acid. It will evaporate off as carbon dioxide and water.
The swell is caused by the now exposed hydophilic (water loving) proteins taking on WATER!
I thought I had this pretty well covered with data at this address:
I just found out that the link that I had to the Protein Data Bank that described this in pretty simple terms is now showing a 404 error. Apparently that page has been eliminated from the website. That's a bummer. Now you guys will never know that stuff you've been throwing away that comes off with the round knives can be made into a food that there is always room for.
Now here's another real life supported with fact web article:
That is a piece of skin that is of like vintage as Bill's. I had mailed that very piece to Uncle George a week ago yesterday. Last I had heard he still hadn't recieved it.
Both the two above web articles are supported with microphotography. In the second article you will see that the collagen fibers are still pretty much intact as structures. You will also see that there IS NOT any acid swell (in spite of acidity) nor water swell. The piece has been rehydrated once, and George will probably do it again a time or two or three.
Bill, here is a real easy and simple test to see what you are dealing with.
Use a hand mirror, or compact mirror, lay it out flat. From the flesh side of the hide, snip off a piece of leather not much bigger than a finger nail clipping. Put a drop of DISTILLED water on the snipped piece. If it swells up, the structural integrity of the fibers has been lost. To see as to what degree, use two straight pins to see how hard it is to tease the snipping apart. If it comes apart like a wet piece of toilet paper, you're probably screwed to the wall. If it is hard to separate, you MIGHT have a chance.
One of the ways that I like to entertain myself is trying to figure out how to chemically manipulate some of these skin structures. This was a citric acid pickled skin at this address:
paul k, I'm going to give you three guesses as to what was used that finally turned that last skin around to the point it was mountable. You're first two don't count................
To part on a sad, sad note. I have as of yet not came up with any way to break the clumped bonds that get created by a formic acid pickle.
The 404 errors I wrote about above just about gave me a heart attack. The pages I was directing to explained in text and graphic illustration what I was showing with my microphotography of the "real thing" as it pertains to tanning.
Protein Data Bank has a new website, and as frequently happens, page addresses are changed and are then not recognized by search engines until the site becomes re-indexed.
Protein Data Bank is a global effort involving the USA, Europe, and Japan to help taxidermists better understand proteins. Well, maybe they had a few other people in mind also.......
Regardless, I found the archieved information on the new web site, and the links on the hidetanning.net pages are working links once again.
This address will take you right in:
It's some really good information, even if you aren't a tanner or taxidermist.
I do find your chemistry smarts quite fascinating, Now I guess I know the difference between acid rot and swell (maybe)(sort of) anyway Im just a simple hack and I do know older tanned skins can be problematic. I've re hydrated skins 10 yrs old with no negative results using just the "universal" method, ie; handful of salt per gallon of water. To recover some stretch I re-oiled using a good grade of tannery oil. A very good way to test the structural integrity you provide us with, I must archive in the back of my mind.
Now I really need to think this over a bit, before I stick my foot in my mouth again as to the 3 guesses
You notice Glen conveniently ignored one small item? "What would you expect to get if you tried to rehydrate a skin that old?" Whatever you call it biologically, I'd still expect a hide that old to turn into instant oatmeal.
It's been very hectic here, sorry I've not been able to follow the threads on this post as quickly as I would have liked, anyway I'll take a stab at it. You stated that the skin (cape) in question was not salted but put directly into a high content sulphate pickle, I'm going to use my first guess (that doesnt count) lol , that you used an aluminum sulphate or high content alum pickle. Now proceed with my spanking..............lol
That can happen when a feller takes in too much new information at once.
You were guessing on the same article that your Uncle George was fishing for answers on. He'll just have to wait. The skin is in the mail.
The question was aimed at the acid swell cape.
When that one was sent to me, and I opened the box, I thought I had just got my butt kicked on that challenge. I started to just throw it in the trash and go on. I should have taken "before" pictures, but I WAS NOT expecting to be able to turn it around.
The running joke around here for a long time was, "Did you try any STOP-ROT on it?". Didn't make any difference if it was a vehicle that wouldn't start, or a computer that wouldn't compute, same old wise crack every time. There's your hint.
I did spend a good number of hours on that cape, but I considered it to be a worthwhile venture. More can be learned from one bad cape than can be learned from a hundred good ones.
As a result, there is now a half a dozen of us that have started working on trying to expand on what was learned and put it to practical use. I really expect we'll come up with "something" before the year is over.
Now I understand what Uncle George means about these microbiolgist people. I think you are using some double reverse phsycology on me now. I really thought the answere would be stop rot, Then again I thought that would just be too simple. Now I'm having a hard time relating the original question to the original post at the same time wondering if you have yet, or are close to getting a process to make these collegan fibers rebond or reform to the point old skins that are structurally weak can be reworked or retanned or restrenghthened for mounting purposes. Wow! Or is that what your trying to tell me?