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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.,
Good morning Richard;
        I learn something every day.Thanks for the details about how
binders need to understand the science as well as the craft of binding with
leather.Your explanation of how suede is "made" clarifies my concept.Thanks
again.
S


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