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Re: dry rotted suede :: maintenance



Thanks Sumner Zacks for the anatomical response from the M.D.
viewpoint. It's wonderful how many fields come together in
bookbinding. My grey cells are getting greyer, but if I recall
correctly, when I was studying leather tanning at National
Leasthersellers' Center in Northampton, England (1978), the grain of
the leather was the epidermis and the corium was the dermis. A suede
had most of the grain sanded off, creating the nap, as distinguished
from a split, in which the grain layer was sliced off, usually by
machine with a rotating blade. Perhaps one of our listmembers in the
leather trade would be kind enough to post a correction or
corroboration. I donated my books on tanning to cba, so can't
reference them at the moment.

Etherington and Roberts have a nice section on leather, and I
suggest everyone take a look at it, particularly the part about
vegetable tanning, and follow all the links, particularly about
fatliquoring.:

http://palimpsest.stanford.edu/don/dt/dt3685.html

When tanning I tend to keep the fatliquoring down, as it makes the
binding and tooling of the leather easier, and I oil the books when
they're finished.

The issue of "preserving" leather with oil is meant for leather in
good condition, not leather which has powdered and needs
consolidation, which is not "restorable", but often through
consolidation will preserve blind or gold tooling, creating the
illusion of leather and retarding the decomposition of the binding.

Dr. Zacks also brings up an interesting point in citing living cows.
There is a great difference in the structure of skins between cows,
calfs, goats, sheep, and pigs, and, of course, the "novelty"
leathers (reptiles, birds, snakes, etc.). The relative thickness and
strength of the grain and corium is of interest to binders. The
strength in goatskin is near the surface of the grain, and in cow
deeper in the corium. A cowhide split can be quite strong-- the
layer without the grain can be stronger than the grain
layer.Splitting and Paring cowhide and using the grain layer on a
binding does not make as strong a binding as goatskin or even calf,
which is thinner originally, coming from a smaller (younger) animal
and has the strength layer closer to the grain layer. Again, I hope
one of our professional leather people will correct this if I'm in
error.

>        This lurker enjoyed your little piece on preserving leather but it
>seemed that a little more precise concept of how leather is organized might
>help find a way to "consolidate".The skin surface (epidermis) of the
>living cow is made of several layers of flat (squamous) cells each covered
>by a very thin cell membrane and interconnected by very ,very small "tight
>junctions". These cell layers are supported by a dermis composed of
>fibrocytes which laydown collagen ,a long stranded protein.This substratum
>contains the blood vessels and nerve fibers needed for a functioning
>integument.Now,when you tan the skin as in leather making,a very rough
>process with scraping,strong acids and alkalis.I doubt much of the
>epidermis (containing cell membranes) survives.What you are dealing with is
>stabilized collagen in leather and destabilzed collagen in powdered
>leather.It seems likely that not only lateral binding is destroyed, but
>also  that the collagen strands are broken into short lengths.If this is
>the case (I suppose someone has studied this),conservators are unlikely to
>find a way to put the together again.,
>S
>

            Richard
            http://minsky.com


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