Following my post the other day asking whether anyone would be willing to give me their deer skins, if they were local to Eastbourne, a comment was made asking me to explain the process. I do a lot of experimental archaeology and part of that involves tanning. The two types are do are brain tanning (BT) and ‘proper’ tanning. BT is not actually tanned leather – it is a process that involves no tannins so cannot be considered true leather. This is only a précis of the process – after all, books are written on the topic.
The first thing to visualize is the skin structure. There are effectively 3 layers – the grain and hair, the corium and the inner membrane. The latter is very thin but the least distinct of the layers. The part of the skin that will result in the wonderfully soft, strong, breathable product that is BT, is the middle layer, the corium.
Once the skin is taken off the animal, all the tallow and remaining pieces of flesh that are inevitably left behind are removed. A metal scraper is used; this is not particularly sharp but does have an edge to it. The skin is draped across a beam and the pressure therefore concentrated in a smallish area at any one time. Our ancestors would have used flint tools known as scrapers. The rounded edge of the tool has, on a microscopic scale, small high and low points, which make it toothed. These teeth catch and remove material but you do have to be careful not to put too much pressure on. This also starts to breaks up the inner membrane. or flint
Once the skin is cleaned, it goes into a bath of potassium hydroxide (KOH). This causes the skin to swell, which facilitates the next step and also helps to dissolve out mucus from the skin. I use KOH straight from the bottle (J) but our ancestors could get the same result from dissolving hard wood ash in water. It is a mild-ish alkali and here’s a tip for those with wood burners. If you get that blackening on the glass from a piece of wood that rolled onto it, when cold, just dip a damp rag in the ash and rub the black. It comes off easily.
After perhaps 2-5 days soaking, depending on temperature, the skin is taken back to the beam and the grain layer is separated. It is pushed off with the metal bar (or flint or an antler/bone bar) and can be seen in the photo. The areas where it has been removed, the places where hair has been removed but the grain still in place, and the areas where the grain and hair is pushed off but not separated from the skin yet (bottom left of image). Once all the grain and hair have gone, the skin has to be neutralized; this is either done by repeatedly changing a water bath, placing it in a stream and allowing it to return the stream’s pH, or adding some weak acid to bring it back to neutral.
It is then time to either let the skin dry, where upon is will go stiff and hard like rawhide, as the hide glues set, or to start the braining. Brains contain emulsified oils and it is these that have to get into the skin to form chemical bonds with the ends of the skin fibres. They can be rubbed into a dried skin or the skin can be immersed in the brain solution. Pulling the skin around, making sure every bit is soaked in the solution is critical – if you don’t get enough oils in, the end product will be hard/stiff in places. The skin is wrung and as much moisture as possible removed (this wrung skin is a tasty treat for any lurking Cocker).
The skin then has to be softened and this has to be one by hand. Whilst the skin dries, it has to be kept moving, to prevent hide glues setting. This is labour intensive and why the process cannot be industrialized. The softening can either be done in a frame (as per images) or by hand. I generally now use a stake – a wood pole, about 4” diameter, in a stand. The end is chisel shaped but not sharp and I use it to stretch the skin across and cause a real bend in it, which also helps break the inner membrane some more. This working has to continue until the skin is completely dry, so it is really a stage best suited to warm days/summers. At the end, and the skin will tell you when, it is a white, soft and stretchy fabric.
If you were to wet it again, it would go back to like rawhide on drying. To ‘set’ the softness, it has to be smoked. All the different ‘aldehydes’ in smoke set the skin structure in the new position so that if re-wetted after smoking, it will still dry soft. The smoking is done over a fire, using rotten wood that is not allowed to burn, only smoulder, and it is easiest if you sew 2 skins together to make a sack so all the smoke has to enter the skin – it cannot go anywhere else. After about 20 minutes, you start to see colour bleeding through, and as soon as there is colour, it is functionally complete. How much more you smoke is up to you and your desired colour. The more you smoke the darker the colour. However, as it is worn and washed, the colour does fade. After the skin is done on one side, then the sack is turned inside out and the other side smoked a bit.
The sack can be opened, the hides separated and then left to air for a while. This helps dissipate the smoky smell (though that will linger for several months) and allows any ‘stickiness’ from the smoke to dry. The BT can be washed, even in a washing machine, though I don’t recommend it, and will dry soft. It is warm when cold, cool when warm but in the wet, it is like a chamois and horrid. Native Americans would remove it in the rain unless they had a waterproof outer – like a cape or oiled leather.
Leather proper, using tannins, can also be made and the other Cocker is not quite as interested in eating it. Deer leather is strong for its thickness and the end product is also soft and pliable. The initial process is the same, but instead of removing the grain, only the hair is removed. The skin is then neutralized and immersed in increasingly concentrated baths of tannins until they are tanned right through. Once done, they are oiled to various degrees, depending on the product required. The sources for the tannins are usually barks, such as oak or chestnut, but anything with high tannin content can be used. I have even used Dock root – try touching your tongue against the inside of the Dock root and you will see how astringent it is - it makes your face pucker. But I am NOT recommending you actually go and do that, as I did the test for you!
Oft asked questions:
This is not the only method to obtain the same BT end product.
Alternatives to brains are available – egg yolks, vegetable or animals oils, such as Neatsfoot, can be emulsified in water using soap, and there are others. But it is surprising how little oil you need – too much and it ruins the project.
Smells are not really bad (IMHO) unless you let the brains go rancid or allow rotting to start. Whereupon you can feed it to the Cockers as it is probably too late to save for BT.
There are various times during the process when you can ‘stop’ e.g. drying to rawhide and it will last for ages, providing it does not get damp, when it will rot.
Finally, the proof is in the wearing – me in a BT suit and footwear. Also doing a bit of flint knapping. Beautiful stuff to wear.
Hope that is of interest to you all and feel free to ask any questions. (And if you do feel generous enough to donate skins, they’ll be welcomed.)