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Re: Brain tanned hides

Hi All,

Brain tanning is a form of oil tanning.  There is nothing particularly magical
about brains, and similar results can be obtained using other fat/oil rich
materials.  In fact, I've seen traditional recipes for larger hides that
include additional fats/oils.  Folks may note that brain tanned leather
resembles chamois, which is another oil tanned leather (beware! 'oil tanned'
is an often misused term in leather retail.).  Basically, the
grain layer of the skin is removed to allow the brain/oil/fat to penetrate
from both sides, the brain/oil/fat is worked into the hide, and the oils
are then oxidized.  It is the aldehydes and other oxidation biproducts that
actually accomplish the tanning (ie. crosslinking of collagen fibres).

The removal of the grain layer results in a suede like finish on both sides
of the skin.  This should be considered if the skin is to be used for
bookbinding, as a suede surface is more likely to become soiled with handling.
I don't think oil/brain tanned leather would take tooling very well either,
but I could be wrong.

The descriptions of the process that I've seen indicate that alot of physical
labour is involved in the process.  The hair side has to be scraped to
remove the grain. Much of it consists of repeated washing
and wringing, etc.  This gets much of the ground substance out of the hide
so that the final product will be more supple (ie. you want the skin to
be a spongy network of collagen fibres will very little 'glue' inbetween).
Also, getting the brain/oil/fat worked into the skin involves a certain amount
of manipulation.

The smoking is a semi-optional step that enhances the oil tannage.

Reed's _Ancient_Skins_Parchments_and_Leathers_ gives an excellent description
of the different tannages.

Cheers, Rick

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