Hydrographic Paper

This name has been given to paper which may be written on with water. It may be made by rubbing paper over with a mixture of finely-powdered galls and sulphate of iron heated till it becomes white. The powder may be pressed into the paper by passing it between rollers or passing a heavy iron over it. A mixture of dried sulphate of iron and ferro-prussiate of potash may be used for blue writing. Or the paper may be imbued with a strong solution of one ingredient thoroughly dried, and the other applied in powder. Paper which has been wet with a solution of ferro-prussiate of potash also serves for writing on with a colourless solution of persulphate of iron.

Iridescent Paper

Nut-galls 8 parts, sulphate of iron 5, sal ammoniac 1, sulphate of indigo 1, gum arabic 1/8th. To be boiled in water, and the paper washed with it and exposed to ammonia.

Parchment Paper

Immerse blotting paper for a second or two in dilute sulphuric acid, then rinse repeatedly in several changes of water, and hang it up to dry. When dry, if it has a crumpled or wrinkled appearance, this can be removed by wetting it, and straining it upon a glass plate, the edges being made to wrap over the plate.

Photographic Paper

See Photography, below.

Tracing Paper

Paper well wetted with Canada balsam and camphine, and dried. Another kind is made with nut oil, and oil of turpentine; the paper is moistened with it, and then rubbed with flour. A temporary tracing paper is made by moistening paper with pure alcohol; it must be used while wet.

Waxed Paper

Lay the paper on a clean hot iron plate, and rub it over with a piece of white wax inclosed in muslin.

Oiled Paper as a substitute for oiled silk

Boiled linseed oil is reboiled with litharge, acetate of lead, sulphate of zinc, and burnt umber, an ounce of each to a gallon. The sheet of paper being laid on a square board, it is well covered with this mixture. The first sheet is covered on both sides, the second, placed on this, receives one coating, and so on to 20, or 50. Separate and hang up to dry. Fireproofing for Paper. Dip in a strong solution of alum, and then dry it. Should the paper he extra thick, the same process may be repeated. Paper Paste. Boil white paper in water for 5 hours; then pour off the water, and pound the pulp in a mortar; pass it through a sieve, and mix with some gum water, or isinglass glue. It is used in modelling by artists and architects.

Papier-Mache

A plastic material, formed of cuttings of white or brown paper boiled in water, and beaten to a paste in a mortar, and then mixed with a solution of gum arabic in size, to give tenacity. It is variously manufactured by being pressed into oiled moulds, afterwards dried, covered with a mixture of size and lamp-black, and varnished.

Papyrine

Dip white unsized paper for 1/2 a minute in strong sulphuric acid, and afterwards in water containing a little ammonia. When dried it has the toughness and appearance of parchment. See Vegetable Parchment.