cuir-bouilli
A method of decorating a book utilizing the
capability of a vegetable tanned leather to be
molded when wet. After being thoroughly softened
in water the leather can be formed or molded into
various shapes, which, on drying, retain those
shapes with a remarkable degree of permanence. The
wet-mold leather can be more permanently set by
drying it under moderate heat, the degree of
rigidity obtained cuir-ciselé being
determined by the drying temperature. A faster
method, and one that produces extremely hard and
rigid shapes, is to dip the molded leather into
boiling water for anywhere from 20 to 120 seconds.
This is the process that gave rise to the name
"cuir-bouilli." Such a process involves the
partial melting of the fixed tannin aggregates in
the leather. At a temperature approaching 100C.
these aggregates become plastic and can be made to
flow and redistribute themselves throughout the
fiber network of the leather. On cooling, the
fibers become embedded in what can best be called
a tough, three-dimensional, polymer network or
resin, somewhat similar to the materials made by
condensing formaldehyde with substances such as
phenol, urea or melamine. The leather actually
sets so hard that some books bound in this manner
required no boards. The decoration itself was
executed by cutting the leather lightly while
damp, after which the design was hammered in
relief. The shaped leather was then immersed in
boiling water, and dried, and the depressions were
filled with molten wax so as to preserve the
designs.
The molding of leather was known in Saxon times in
England, and was widely practiced during the
middle ages in both England and on the Continent.
The motifs used were generally mythological
animals and interlaced foliage. In the late 19th
century interest in the molding of leather was
revived and used extensively for many objects,
including bookbindings. (94 , 236 , 291 )
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