Page:The Art of Bookbinding, Zaehnsdorf, 1890.djvu/131

Rh half-bound work, but for extra work it is far better to sprinkle, marble, or otherwise colour the leather when on the book. Hand-colouring is coming again into use, and by degrees getting known more and more throughout the trade; but a great many secrets in the art have been lost. Before giving the names of the chemicals to be used, I must give a general caution, that if any acid be used on the leather, it is essential to wash as much as possible of it out with water immediately after it has done its work, or after a few months the surface of the leather will be found to be eaten away and destroyed. It is a fault of some of our binders at the present day, that if they use any chemical, either on their leather or on their paper, they are not satisfied to use their acid weak, and allow it to do its work slowly, and when the proper moment has arrived stop its further action, they frequently use the acids as strong as possible, and, either to save time or through ignorance of their chemical properties, do not wash out the residue. The consequence is, the leather or the paper rots. In order to avoid this, I will not recommend any chemicals that will destroy the leather, but give instructions for harmless preparations, by the use of which as great a variety of different styles may be executed as will, I trust, satisfy any reasonable expectation.

Black.—Sulphate of iron or copperas is the chief ingredient in colouring calf black. Used by itself, it gives a greyish tint, but if a coat of salts of tartar or other alkali be previously used it strikes immediately a rich purple black. The name copperas is probably from the old and mistaken idea that the crystals contain copper. They have a pale greenish blue colour. It can be purchased at the rate of one penny per pound from any drysalter.

1. Into a quart of boiling water, throw a $1/4$-lb. of sulphate of iron, let it re-boil, and stand to settle, and then bottle the clear liquid for use.