marccarlson20 at hotmail.com
Thu Apr 10 09:24:42 PDT 2003
Mmm. "Tanning" (and for that matter 'leather') is a term that has a
specific technical meaning, as well as a more general definition. Just to
bore you (since you should know better than to ask open-ended questions like
this :) ) There were essentially 5 ways of processing skin that would be
appropriate for the Middle Ages. The first, and easiest, is to just cut to
whatever size and purpose you want it for right now, and let it dry that way
as rawhide (we actually had an example of a shoe pattern this last week at
shoemaking that would have been great, and perfectly appropriate, made with
rawhide - and could be made in one day).
The second is oil curing, in which you take the skin, and massage oils into
it (the trick here is, I understand, to trigger an oxidization reaction in
the skin with the kneading and manipulation). This was likely the most
ancient of the actual processes, but it's hard to know since oil cured hide
will not last over the centuries).
Then there's mineral curing or tawing. Alum tawing has been described, and
is a VERY period way of dealing with hides (and if people are smart, they
may want to start trying to talk Montega into teaching people how to do it -
with classes and such).
The only real problem with any of these preceding methods is that they are
not really all that stable, particularly when you get them wet. Most of
them will eventually revert to wet skin [which is why -technically- it can
be argued that they aren't "leather", per se - although they are still
generally referred to as such].
Then we get to _tanning_, in which there is a real alteration to the skin to
something that is chemically stable and won't revert back to rawhide when
soaked in water.
First is smoking the skin over a wood fire, and application of fat (or
brain) material to keep the skin more supple, which doesn't do a really good
job, but is better than nothing. The wood smoke releases various aldehydes
and phenols into the skin that simulate -true- tannage. There is some
argument that this process dates back as far as the late Neolithic at least,
based I believe on the Iceman's garments.
True tannage is what we call today "vegetable tan", although even that
should be differentiated between modern vegetable tanned and "pit tanned"
leathers. Traditional tanning involved soaking the skins in a rich tannin
solution for months. Today it is done in a matter of weeks with highly
concentrated solutions that produce a similar, but different product. True
pit tanned leather has some different properties (it's harder when dry,
softer when wet, is more durable) and is just freaking expensive these days.
(Sources upon request)
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