Re: MtMan-List: period tanning / Alans comments

[John Kramer <kramer@kramerize.com>]

Matt, Bob and Alan,

Great thread.  The link to "The Pennsylvania Gazette" is invaluable.

One receipt from 1825 calls for white vitriol (sulphate of zinc), cream of
tartar, sal ammoniac (muriate of ammonia), vitriolic acid (sulphuric), nitric
acid, spirit of salt (hydrochloric acid), oak bark, sumach, elm bark,
sassafras, lignum vitae, and water.  All in the same receipt.  

Some receipts are quite simple and only include one or two materials, some are
very complex; I've always considered all of the ingredients a part of the
tanning process.  Bark tanning can produce very hard leathers which are
primarily what we see today; the old receipts include many other techniques in
combination with bark and seem to indicate supple leathers could also be
produced using bark.

From the same period I have recipes which include dog and pigeon dung used
with
water and sumach, several call for soaking in a fermented liquor of bran and
water, some with and some without oil, alum or tannin.  One oil tan receipt
makes extensive use of both quicklime and slacked lime in preparation for the
oiling which follows a long soak in fermented bran liquor.

I asked about the term "dressing" as all of the old receipts I've encountered
using this term only refer to mixtures which are applied to finished goods for
preservation or protection.  

Oil, alum and other leather receipts are included with the tannin based
receipts and all are called "tanning" even though the only early 1800's
definition I've encountered states that tanning is to saturate a skin with
tannin to promote the slow combination with the gelatine, albumen and fibrine
contained in the hide.  Pretty much what you said only not as technical.

If I get some extra time I'll dig out some references to some of the other
materials.  Time has recently been in short supply, for quite a while.

More old receipts I've found include alum than even bark, the acids and
arsenics are more unusual.  The best "tan" oak was taken from the Live Oak
tree
which is in short supply today, most common now in Texas and I think
protected.  As you said many trees were used for tanning in the past.  

RE: urine tan;  have you ever smelled cheap modern Mexican garment or
upholstery leather after a rain storm?  They couldn't be using anything else. 
I'll keep an eye out for the old reference buried somewhere in my piles of
stuff.  

Many of the old methods we will never know as they were amongst the "secrets"
of a trade: and protected by the Masters of the guilds.  A very common problem
when working with old ways.

John...

At 02:45 PM 12/17/98 -0700, you wrote:
>Johns reply to my comment of not knowing of any other period tanning methods
>besides bark, brain, oil and alum was:
>
>Except for oil tanning, egg tanning, urine tanning, buttermilk tanning, sour
>>milk tanning, arsenic tanning and acid tanning.
>>
>
>I guess a lot has to do with how we define our terms. The term 'brain
>tanning' did not exist to my knowledge before modern times. The accepted way
>(among the leather industry) of defining tanning terms is based on how the
>actual chemical change is affected on the leather. If something actually
>changes the collagen proteins of the skin, permanently, it is a 'tanning'
>agent.
>
>I am well aware that there was an incredibly wide variety of substances used
>and substituted in various tanning recipes throughout the ancient
>world....but often it is still considered the same method of tanning. From
>the example above 'sour milk tanning, buttermilk tanning, and egg tanning'
>are generally considered the same thing as 'brain tanning' as they affect
>the leather in the same way. Soap tanning does too. Oil tanning is a
>different process because the fish oils (usually cod) oxidize extremely
>easily, and in this oxidation they create polymers which change the collagen
>fibers of the skin. You can not wash out the effects of true 'oil tans'
>There is actually reasonable speculation that this type of tanning was being
>done by many native tribes in the northwest, and was clearly done by
>Europeans of this era on many of the deerskins that were exported to that
>continent. Oil tanning is a term that is commonly thrown around by people
>any time an oil is added to the tanning mix, not really knowing what it
>means.
>
>As far as urine tanning goes, I'd love to see some evidence of this. I've
>met one man so far, who claims to have actually seen someone 'urine tan' and
>he has described it to me in detail....so I'm gonna try it. But for the most
>part, it seems to be a term that is thrown around, with little real basis.
>Urine was commonly used by NW Coast and Arctic people to strip the oils out
>of skins that were otherwise just too dang oily to do anything with, but not
>as a 'tanning' agent.
>
>And while there were many, many sources of tannins for bark tanning, its
>still just considered bark tanning. The hides you are referring too that
>were sent from San Franciso to Boston, were destined for bark tanneries (and
>soon a huge bark tanning industry developed in California based on Tan Oak).
>
>Lime and saltpeter were both used in many traditional tanning methods, but
>neither is a 'tanning' agent, and wouldn't be known as 'lime tan' or
>anything like that. Lime was used in the first recorded account of Comanche
>brain tanning, and is standard in chrome tanning and bark tanning.
>
>As far as arsenic and acid (besides tannic) tans go, these are modern
>methods as far as I know. Do you know of any references to these being done
>during or before the period we are talking about?
>
>
>You asked what I thought of the comments about brain tanning being a
>dressing rather than a true tanning.....
>
>I do not know what the accepted definition of tanning was back in the early
>1800's, but in modern times, 'tanning' occurs when the protein fibers
>(collagen) are permanently changed in their composition, so that the skin
>can never go back to rawhide. Brains do not do this, unless they do a very,
>very, weak oil tan (by oxidizing).....and I think it is more accurate to
>call it a dressing (experimenting with, I have successfully completely
>removed all of the effects of the braining by putting a brained and softened
>hide in a running creek for three days....all of the tactilely discernable
>effects of the brains were gone, it was rawhide again)....however smoke does
>tan a hide.
>
>Smoke contains a gaseous form of formaldehyde which is why it preserves
>stuff (and one reason that it is carcinogenic). It causes the collagen
>proteins to form new links to one another at different points on the protein
>chain (this is all in leather chemistry books if anyone is real interested I
>could give you some good titles). In graphic terms, it causes the fibers to
>form little bridges between one another that are permanent. You can not wash
>out the effects of the smoke....the color will wash out, but not the
>'tanning'. It'd be more accurate if we all referred to it as 'smoke tanning'
>and 'brain dressing' like some folks do....but the term 'brain tanning' is
>popular and here to stay.
>
>As a side note, 'Alum Tanning' is not generally accepted as a 'true' tanning
>method, because the affects can be easily washed out. That is one reason it
>is generally referred to as 'Tawing' rather than tanning.
>
>A great book on ancient tanning methods and recipes from throughout the
>world, with excellent yet understandable explanations of the chemistry and
>related processes is 'Ancient Skins, Parchments, and Leathers' by Ronald
>Reed. It also talks about the conversion of parchments to leathers that you
>were referring too.
>
>Matt Richards
><http://www.braintan.com/>www.braintan.com
> 
Use it up, wear it out, make do, or do without.
John Kramer  <kramer@kramerize.com>