Bookbinding and The Care of Books
Librarians by Douglas Cockerell with Drawings
by Noel Rooke and other Illustrations
New York
1902
Book binding Chapter XIX
Part 4
generally condemn the use of tanning materials
belonging to the:: catechol group, although the
leathers produced by the use of these materials are
for many purposes excellent, and indeed superior.
The class of tanning materials which produce the
most suitable leather for this particular purpose
belong to the pyrogallol group, of which a well
known and important example is sumach. East
Indian or 'Persian' tanned sheep and goat skins,
which are suitable for many purposes, and are now
used largely for cheap bookbinding purposes, are
decay in less than twelve months, and the sub-committee are inclined to believe that no book
bound in these leathers, exposed on a shelf to sunlight or gas fumes, can ever be expected to last
more than five or six years. Embossing leather under heavy pressure to imitate a grain has a very
injurious effect, while the shaving of thick skins greatly reduces the strength of the leather by
cutting away the tough fibers of the inner part of the skin. The use of mineral acids in
brightening the colour of leather, and in the process of dyeing, has a serious effect in lessening
its resistance to decay. A good deal yet remains to be learned about the relative permanency of
the different dyes."
On analysis free sulphuric acid was found to be present in nearly all book binding leather, and it
is the opinion of the committee that even a small quantity of this acid materially lessens the
durability of the leather.
" It has been shown by careful experiment, that even a minute quantity of sulphuric acid used in
the dye bath to liberate the colour is at once absorbed by the leather, and that no amount of
subsequent washing will remove it. In a very large proportion of cases the decay of modern
sumach-tanned leather has been due to the sulphuric acid used in the dye bath, and retained in
the skin. We have examined very many samples of leather manufactured and sold specially for
bookbinding purposes, from different factories, bought from different dealers, or kindly
supplied by bookbinders and by librarians, and have found them to contain, in a large number
of cases, free sulphuric acid, from 0.5 up to 1.6 per cent."
The publication of the report should tend to fix a standard for bookbinding leather. Hitherto
there has been no recognized standard. Bookbinders have selected leather almost entirely by its
appearance. I t has now been shown that appearance is no test of durability, and the mechanical
test of tearing the leather is insufficient. Sound leather should tear with difficulty, and the torn
edges should be fringed with long, silky fibers, and any leather which tears very easily, and shows
short, curled-up fibers at the torn edges, should be discarded. But though good bookbinding
leather will tear with difficulty, and show long fibers where torn, that is in itself not a sufficient
test; because it has been shown that the leather that is mechanically the strongest, is not
necessarily the most durable and the best able to resist the adverse influences to which books are
subject in libraries.
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