Page:The Art of Bookbinding, Zaehnsdorf, 1890.djvu/162

126 different kinds of leather require such different degrees of heat, that what would fail to make the gold adhere upon one leather would burn through another. The various colours each require their different degrees of heat; as a rule, light fancy colours require less heat than dark ones. The finisher has not only to contend with these difficulties, but he must also become an adept in handling the gold leaf and in using the proper medium by which the gold is made to adhere to the leather. This medium is used in two way—wet and dry. The wet is used for leather, the dry for velvet, satin, silk, and paper. The wet medium is again divided into two classes, one for non-porous and another for porous leather. Morocco is the principal of the non-porous leathers, with roan and all other imitation morocco.

The porous varieties consist of calf of all kinds, russia, and sheep. The non-porous leathers need only be washed with thin paste-water or vinegar, and glaired once; but if the glaire be thin or weak it will be necessary to give them a second coat. The porous varieties must be paste-washed carefully, sized all over very evenly, and glaired once or twice; care being taken that the size and glaire be laid on as evenly as possible. All this, although apparently so simple, must be well kept in mind, because the great difficulty that apprentices have to contend with is, that they do not know the proper medium for the various leathers, and one book may be prepared too much, while another may have a deficiency, and as a consequence, one book will be spoilt by the preparation cracking, and the gold not adhere to the other. By following the directions here given the finisher will find that his gold will adhere without much trouble, beyond the practice necessary in becoming accustomed to an accurate use of the various tools.