Many copying papers act by virtue of a detachable pigment, which, when the pigmented paper is placed between two sheets of white paper, and when the uppermost paper is written on, transfers its pigment to the lower white sheet along lines which correspond to those traced on the upper paper, and therefore gives an exact copy of them on the lower paper.

The pigments used are fine soot or ivory black, indigo carmine, ultramarine, and Paris blue, or mixtures of them. The pigment is intimately mixed with grain soap, and then rubbed on to thin but strong paper with a stiff brush. Fatty oils, such as linseed or castor oil, may be used, but the grain soap is preferable. Graphite is frequently used for black copying paper. It is rubbed into the paper with a cotton pad until a uniform light-gray color results. All superfluous graphite is then carefully brushed off.

It is sometimes desired to make a copying paper which will produce at the same time a positive copy, which is not required to be reproduced, and a negative or reversed copy from which a number of direct copies can be taken. Such paper is covered on one side with a manifolding composition, and on the other with a simple copying composition, and is used between 2 sheets of paper with the manifolding side undermost.

The manifolding composition is made by mixing 5 ounces of printers' ink with 40 of spirits of turpentine, and then mixing it with a fused mixture of 40 ounces of tallow and 5 ounces of stearine. When the mass is homogeneous, 30 ounces of the finest powdered protoxide of iron, first mixed with 15 ounces of pyrogallic acid and 5 ounces of gallic acid,' are stirred in till a perfect mixture is obtained. This mass will give at least SO copies on damp paper in the ordinary way. The copying composition for the other side of the prepared paper consists of the following ingredients:

Printers' ink....... 5 parts

Spirits of turpentine. 40 parts

Fused tallow....... 30 parts

Fused wax......... 3 parts

Fused rosin........ 2 parts

Soot.............. 20 parts

It goes without saying that rollers or stones or other hard materials may be used for the purpose under consideration as well as paper. The manifolding mass may be made blue with indigotin, red with magenta, or violet with methyl violet, adding 30 ounces of the chosen dye to the above quantities of pigment. If, however, they are used, the oxide of iron and gallic acids must be replaced by 20 ounces of carbonate of magnesia.

Celloidin Paper

Ordinary polished celluloid and celloidin paper are difficult to write upon with pen and ink. If, however, the face is rubbed over with a chalk crayon, and the dust wiped off with a clean rag, writing becomes easy. Cloth Paper.—This is prepared by covering gauze, calico, canvas, etc., with a surface of paper pulp in a Foudrinier machine, and then finishing the compound sheet in a nearly similar manner to that adopted for ordinary paper.