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Re: [BKARTS] processing skins



>I was at a western craft leather show recently, geared towards makers of
>saddles, chaps, etc., and bought some beautiful tanned salmon skins. Not
>having a sound background in how skins are generally processed, I'm very
>curious as to how a material that I think of as having very little strength
>(I'm stuck thinking of the salmon skin on a dinner plate) can be transformed
>into something that looks so durable and leathery.
(snip)
>
>Thanks in advance for and info and insights.
>
>all the best,
>Roberta
>
>
>Roberta Lavadour - Pendleton, OR
>Mission Creek Press  -  Desultory Press
>http://www.missioncreekpress.com


Here is one method of preparation of fishskin, as described by Lotta Rahme,
in her book:
_Leather; Preparation and Tanning by Traditional Methods_
by Lotta Rahme.  The Caber Press, Portland, OR  2001.

I bought the English language rights to her book, had it translated, and
published it.  Still in print @ $19.95 + $3.50 P&H.

http:home.swipnet/lottastannery is the link to her website in Sweden.

Jack


Urine tanning chemistry
Within the leather trade, urine has been used for dehairing  skins, for
tanning skins and for washing skins.
Urine contains formic acid and urinase, and uric acid, among  other things.
These acids have a preservative effect on the  skin.
When urine is left to stand ammonia is formed, which is a strong base.  If
a hide sits in urine for some time, the basic environment will begin to
have a dehairing effect.
The ammonia influences the skin by splitting the naturally  occurring fats,
to form glycerol and free fatty acids.  These free fatty acids can
penetrate the hide and react with the fibers of the dermis; the skin is
tanned.  When ammonia is used as a cleaning liquid, it is it's saponifying
properties that are being exploited.

I have made a few tries at urine tanning of fish skin.  The  recipes I
started with come from Rita Pitka Blumenstein, who lives on Nelson Island
in southwestern Alaska.  She relates  the following:

"Fishskins were used for mukluks, mittens, water carriers,  and
raincoats....The king salmon is used for boots, heavy-duty  boots.  Only
female silver salmon is used for hats for girls.   And the pike skin is for
water jugs.  The trout is for  bags....
"You take the skin off and soak it in the water, and then you  scrape it
with a sea shell.  Some fish you have to scale;  some fish you don't.  Like
pike and white fish, you've got to scale it, you  soak it in urine.  The
urine has to come from a young boy baby before weaning.  It doesn't contain
any chemicals, just momma's milk.  For thicker skins, you have to  use the
urine from an older boy, around the time his voice  changes.
"[The skin soaks in the urine] sometimes half a day, sometimes overnight.
The longer you soak it, the softer it gets.  Then my mother used to
use[Fells] Naphtha soap, and she sudsed it in the  water and then cooled
off the water and then put the skin in  it.  Then she puts aspen shavings
in the water and cools it off, then you rinse it in clear water and wring
it out.  My mother used a towel to absorb the water.  I  asked her one time
in camp, 'What did you use when you didn't have cloth?'  She said they used
dried moss.  And then you put  it on a smooth board, stick it there, the
inside facing in.   Then when it dries, it will just peel off itself.  You
store it away, and when you are ready to use it, you wet the shavings that
you saved, and you pad them onto the fishskin  on the outer side.  Then you
roll it and leave it until it  dries.  Then you shake it off." [Hickman
1988: 19ff.]

I have started from this recipe but have used woman's urine  for 10-12
hours and then rinsed the skins, washed them in  water with soap, laid them
in a willow bark bath 10-12 hours, greased them with, for example, train
oil, dried them and softened them.

Thompson Conservation Lab.
7549 N. Fenwick
Portland, OR  97217
U.S.A.

503/735-3942

http://www.teleport.com/~tcl

"The lyfe so short; the craft so long to lerne."
Chaucer  _Parlement of Foules_  1386

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