Report of the Committee on leather for bookbinding . and pigskin may be speciallynamed, as well as calf and sheep for some kindsof binding, it is found impossible to get sufficientfirmness and solidity by the use of sumach only;and in these cases the use of oak bark, alone or inmixture with sumach, may be recommended; as ithas been proved that a slow bark tannage is scarcelyinferior to sumach in resistance to decay, while sur-passing it as regards mechanical wear. Chromeleathers produced by basic salts of organic acidsand free from mineral acids and sulphur, and com-binations of such chrome ta
Report of the Committee on leather for bookbinding . and pigskin may be speciallynamed, as well as calf and sheep for some kindsof binding, it is found impossible to get sufficientfirmness and solidity by the use of sumach only;and in these cases the use of oak bark, alone or inmixture with sumach, may be recommended; as ithas been proved that a slow bark tannage is scarcelyinferior to sumach in resistance to decay, while sur-passing it as regards mechanical wear. Chromeleathers produced by basic salts of organic acidsand free from mineral acids and sulphur, and com-binations of such chrome tannages with pyrogalloltans, have stood satisfactory tests; and while timealone can prove their durability, it is very probablethat it may exceed that of vegetable tannages. Theiruse in bookbinding must, however, be regarded asto some extent experimental. Whatever tanning material is used, it is impor-tant that the process should not be carried too object of tanning is simply to preserve theanimal tissues of the skin from decay, and to in-60. PHOTOMICROGRAPHS OF GRAIN OF VARIOUS SKINS.(A. Seymour-Jones.) 1. Cow Hide. 2. Calf Skin. 3. East India Goat. 4. Pig Skin. 5 East India Sheep. 6. Welsh Sheep. [ To face p. 6o. LEATHER FOR BOOKBINDING crease its resistance to water. The tanning processhas throughout a hardening effect on the fibre,which diminishes its toughness, and, if pushed toits extreme, ends in brittleness and loss of samples of old leathers which are still in agood state of preservation have been tested by theSub-Committee, and in all cases they have beenfound to show a smaller proportion of tannin to hidefibre than is common to modern leathers, while inmany cases overloading with tannin has been foundto be an actual cause of decay. The practice ofretanning or re-sumaching already tanned leathersto give additional softness and fulness is speciallyobjectionable. The use of strong mineral acids, either duringthe tanning process or for the preservati
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Keywords: ., bookcentury1900, bookdecade1900, bookidcu, booksubjectbookbinding
