When preparing a hide for the natural tanning process it is important to think about removing fat, controlling bacteria and avoiding bug damage. That means several things.
First, you need to remove all the excess meat and fat from the hide. Note: It is your butcher’s job to take the skin off the animal leaving the carcass intact. They deal in the meat side of things. That is their focus. They are not interested in what happens to that hide once it leaves their shop. They will not remove enough of the meat and fat off the hide for proper preservation.
Second, you need to make sure you get a good layer of salt on the entire hide as soon as the fat and meat have been removed. This is a very time sensitive task. All of this must be done on the day of slaughter. If you cannot get to it that day, you must keep the hide in a cooler to be worked the next day or in a freezer to be dealt with when you can.
We have prepared a 90-second video showing the process along with some detailed instructions and photos on our website: Driftless Tannery Services.
Why the fuss? Chances are if you have used a chemical tanner in the past, you did not have to do all of these steps. You may have gotten away with just throwing some salt on the hides, drying them and sending them in. I’m guessing you got back a clean white hide with fluffy straight fiber. That is what was returned to me the times I sent my hides to a chemical tanner.
Here is the difference between us and them, and why we started Driftless Tannery to begin with: we do not use harsh chemicals that are unsafe for ourselves, our staff or the environment. The chemical tanners use bactericides, chemical scours, bleaches and other chemicals to kill bacteria and strip the oils from the hide and the fiber. We do not. We use gentle, eco-friendly soaps to clean the hides and food grade citric acid and salt to keep the bacteria at bay. We are working with a tanning chemist to obtain an eco-friendly degreaser but that is not yet available. In our process, that means we must physically remove the fats from the hides.
Leaving a layer of fat on the hide prevents the salt from penetrating and preserving the skin as shown in the photo below on the left. If you try to store a hide that is covered in fat, larder beetles will find that hide and begin to eat away at it. That is their job and they do it well. (I think I’ll write an entire blog on the larder beetles as they are fascinating little creatures.) Below middle you can see photos of larder beetle damage. This damage can be identified early.
Bacteria will find a safe haven beneath that fat. The bacterial damage doesn’t become obvious until we rehydrate the hide and get it moving through our process. Sometimes it shows itself as hair slippage when we wash the hides. Other times it shows up as we begin to take the membrane off the hide. At that time a hide with bacterial damage will easily tear, whereas a well-preserved hide will not tear. If it gets through the wash process and doesn’t tear on the beam when we are removing the membrane, the damage shows up in our finishing area as just a weak, oftentimes pitted hide. You can see the bacterial damage on the finished hide pictured below right.
Then there is the issue of grease. Hides that have been stored with the fat on do not easily let go of that grease. That grease interferes with the wash process as we can’t get the hides back on a beam until it is rehydrated. We rehydrate and wash the hides at the same time. So, the hide that gets sent to us with a half inch of lard on the back gets tucked in a sink and washed. We can’t get to removing that fat until the wash process is over and we have put the hide into our pickle solution (citric acid and salt bath) for 24 hours to swell the membranes for removal. If we were to try to wash the hides again at this point, we risk something called acid swell. That is a whole other topic requiring some basic chemistry knowledge. Another blog topic for another time.
These fatty hides that get their membrane and fat removed after the pickling process can still be greasy. We only have mechanical means at that point to deal with the grease. Scraping, scraping and more scraping. Any grease left behind will interfere with the tannin uptake leaving portions of that hide untanned. Sometimes that grease is obvious and we can address it, sometimes it is not. You can see an example of a greasy hide that went through our alum tawning process in the video below.
This is why we urge all our clients to properly cure their hides before sending them to us. If you send us a hide with bacterial issues, we won’t be able to fix it. We can run it through our process but the result isn’t going to be perfect.
We a will do all we can on our end to care for and preserve your hides, but the quality of the final result depends on how it was initially preserved. We want to give you back a product that you are happy with. To do that, we need your help with the first step.
Thank you for reading and for being interested in how the natural tanning process works. If you ever have any questions or need help along the way, we are here for you. After all, you are why we do what we do.
Here is a quick video showing what could happen if there is too much fat on a hide and an example of a bacteria damage on a tanned hide.