Page:The Art of Bookbinding, Zaehnsdorf, 1890.djvu/204

164 case be plunged in warm water afterwards, to wash away the lime and acid, and, after drying, it should be sized.

Ink stains (marking ink, silver) may be removed by a solution of tincture of iodine; nitrate of silver, the basis of the ink, is changed into iodide of silver, this is then treated with a solution of cyanide of potassium. It may perhaps be necessary to repeat this two or three times; when quite dissolved out, it must be well washed. As the cyanide is a deadly poison, one may subsitute hyposulphite of sodium.

Fat stains.—(1.) Place a piece of blotting-paper on each side of the stain, apply a hot polishing iron very carefully to the paper; this will, in most cases, melt the fat, which will be absorbed by the blotting-paper.

(2.) Scrape pipe clay, or French chalk, which place on the stain, then use the hot iron. The iron must not be used too hot, or the paper will be scorched; a piece of paper should always be placed between the iron and the leaf stained. The powder may be afterwards brushed away.

(3.) May be removed by washing the leaf with ether, or benzoline, placing a pad of blotting-paper under and over the leaf, dabbing the benzoline or ether on the spot with a piece of cotton wool. This process must not be conducted near a flame, both are highly inflammable.

(4.) A mixture of 1 part nitric acid, 10 parts water, is useful in many instances for oil stains. When erased, plunge the whole sheet or leaf into water, changing the water several times. Dry and size.

Ink.—When the writing-paper has been made from inferior rags bleached with excess of chlorine the best ink becomes discoloured.

Reviving old writings.—(1.) Brush the paper over carefully with a solution of sulpho-cyanide of potassium (1 in 20). Then, while still damp, hold over a dish containing hot muriatic acid; the writing will develop deep red.