BRAINS & ALTERNATIVES TO BRAINS
Brains are one half of the ingredient we use in smoke-tanning to get hides tanned.
The other half? Smoke.
So you guessed it, smoke-tanning is also called “brain-tanning" + when you hear “brain-tanning” you know smoke is involved.
We use brains because they are made of a very important substance, a constituent our ancestors identified and utilized millennia ago.
Read on.
Brain is a verb
The historical English verb for applying brains to a hide is fat-liquoring. ‘Liquor’ is an old term for a liquid, typically a liquid made of exciting things. (This is why we also call a tannin-tea a bark-liquor.)
But more than likely, you'll hear hide tanners call the act of applying fat braining.
When we brain a hide, we lubricate the structure of the skin itself. A skin's structure is primarily collagen, a protein. The shape of collagen is like woven threads. I think of the woven threads like a coiled basket, as this is what they actually look like under a microscope. And just as there are multiple types of weaves + weaving aesthetics, every species of animal hide has a different configuration of woven threads. This is one reason why they all have unique characteristics and make specific leather products.
Lubrication is the result of chemistry-based interactions. Collagen fibres are made of amino acids. Amino acids are polar, with one end open to receiving water. This state of receptivity is called being hydrophillic ("water-loving"); and the act of amino acids (and therefore, collagen) bonding with water liquids is called a hydrophillic interaction. Skin likes being hydrated; we know this. Then there are the brains. Brains contain lecithin, a collective term for phospholipids that have a fatty end and a polar end. This polar end - kaching - can bind with the polar end of the collagen. So now we've got two hydrophillic ends of different substances, bonding together. The other end of the lecithin is the fatty end. It hasn't bonded to the collagen, it's just hanging out. The fibres therefore get lubricated, being coated by the oily nature of the lipid (fat).
When collagen fibres are lubricated, they relax. Instead of a rigid coiled basket with firm structure, they're flexible. They are also wet. This is because we, the tanners, mixed brain with water - that's the fat-liquor - and helped facilitate this hydrophillic interaction even more. There are other ways to encourage brain to absorb into hide without water, but water is definitely a direct route.
Our goal now is to get the hide to dry, while keeping that flexibility and lubrication in inact. This means the next step is to either smoke or soften the hide, but ultimately, both.
Brains and not-brains
Animal brain is considered by most tanners to be the best found substance for smoke-tanning. I say “found” substance to mean: nothing about it has been altered; it is what it is.
If you'd like to see a video on how to harvest animal brain from a deer skull, {you can watch here.}
But tanners disagree when it comes to the * best * alteration or substitute for brains - and whether these substitutes are actually better than brains.
Here's a few options:
Egg yolks
Egg yolks are how we know about lecithin as a molecule. Chemist Théodore Gobley identified it in 1845 and name it after the Greek word for, literally, egg yolk; lekithos.
Egg yolks are comprised of up to 75% lecithin. This is 3x the comparative amount that soybeans contain.
And egg yolks are small. IMO, we need a lot of them - over a dozen - to lubricate one hide. Even then, something about their particular brand of phospholipids just doesn't do it for me. I find they make buckskin that is less creamy, relaxed, + easy to drape than the buckskin made through animal brain. This can be overcome, however, if we add a few spoonfuls of a fixed oil (like grapeseed) to our fat emulsion.
Egg yolks also contain that other 25%+. This includes proteins and minerals. I am not a chemist; I can only wonder if the presence of proteins + minerals (these are structural, not lubricatey, in nature) has an impact on the hides that make them take on more heft than I like to see in my leather cloth.
Egg yolks also can't be overheated before being applied to hide. If cooked, their proteins reconfigure and the yolks can no longer bond with collagen.
That being said, hidework is in the eye of the hide tanner. I know many farmers who prefer working with their flocks' eggs than to source fatty substances elsewhere.
Liver
Incorporating an animal's liver in addition to its brain is a widely-held approach to smoke-tanning
Liver contains a wide variation of lecithin quantity, potentially dependant on an animal's diet. It is likely for this reason that liver is an historic but not primary source of collagen lubricant - more often playing a supporting role in a multi-constituent fat emulsion recipe.
While the lecithin content of liver is not closely studied, the choline content is often measured, as it is isolated + used in the supplement industry. Choline is a nutrient, often housed in lecithin (if you buy choline supplements, you're likely taking them in lecithin). A single beef liver contains about .3 grams of choline.
Liver also should be used raw when used as a collagen lubricant. As a raw substance, it can be squished into a near-liquid form. Once cooked, it hardens.
Full disclosure: I myself have not (yet) used liver in tanning; it's something that's been shared with me and read about in the old books.
Lecithin
Lecithin itself is now isolated in labs…a lot. It is used in pharmaceuticals, baking, supplements, cosmetics. {So. many. things.} Luckily for hide tanners, this means we can access lecithin easily and with little cost. That is, if you aren't opposed to foregoing found substances + using altered ones for tanning.
The primary source of isolated lecithin is soy; the second is sunflower. I recommend sunflower lecithin, as its harvesting and processing is much more gentle on the land than that of soy's. It is also non-GMO and typically organic.
Individual hide tanners' recipes vary; generally 1 teaspoon to two tablespoons is all you need for a deer hide, plus a solid fat to pair with it.
Soap
Soap doesn't naturally contain lecithin, although lecithin is often added to soaps to enhance their emulsifying qualities. We get soap through a completely different process: the combination of lye + fat. This combination results in the same conditions we want for collagen lubrication, through a totally unrelatedm eans.
When lye and fat combine, they form a substance with one hydrophillic end and one lipidphillic end (just like lecithin!). The lipophillic end is responsible for cleaning up grease in a sink full of dishes. The hydrophillic end is the one that can acts as a vehicle to get fatty substances into our hides.
{Watch this cute old school video circa 2013} on how our ancestors may have originally found soap + for a detailed explanation of how salts of fatty acids arise and do their work in the world.
To use soap instead of brains, I fill a measuring cup to ⅓ cup + add 2 tablespoons of a fixed oil (like grapeseed) for my fat emulsion.
Any and all of the above ingredients can be combined with each other. Experiment, see what you like, and develop your own recipes. This is part of how we make our own hide tanning style.
Despite the recent vintage of the molecular name, humans have known about lecithin as an important source of material + chemistry-based pursuits.
It's something I love about hide tanning: the way it reveals humans' rigorous scientific methodology that reaches back millennia.
We started with hides; {now we also study biomedicine} Our constituents of study are the same.
Our current scientific pursuits can enhance our traditional ones - and importantly, vice versa. Our historical + traditional pursuits can give us a moral, social, and cultural framework to approach contemporary scientific study.