Luminous paper is prepared by compounding the pulp with gelatine and phosphorescent powder.
♦Transparent paper♦
Transparent papers are made by several different methods. The usual one employed is to apply a thin coating of a solution of Canada balsam in turpentine, or a solution of castor or linseed oil in absolute alcohol, the alcohol in the latter case being permitted to evaporate, thereby rendering the paper transparent. Such paper is largely used for tracing purposes, and may be restored to its original state of opacity, with the tracings left unchanged, by removing the oil with a fresh bath of alcohol.
♦Safety♦
Safety-paper is a paper so treated or coated with chemicals that any ink-writing upon its surface cannot be erased, effaced, or removed without leaving indelible marks on the paper. As its name implies, it is used for safety in bank-checks or other commercial paper, to protect against alteration.
Gunpowder-paper is prepared by spreading an explosive substance on paper, which is then dried and rolled up in the form of a cartridge.
♦Sand and emery♦
Sand and emery papers are produced by coating a stout paper with glue, and then sprinkling sand or emery-dust upon the surface. Man’s skill has devised for this purpose an ingenious machine. This first coats the paper with glue from a revolving brush, which plays over the surface of melted glue in a steam gluing-pot below. Having accomplished this result, it softens the glue with a spray of steam, and sifts the sand upon the surface, all surplus sand dropping into a box below as the sanded or emery-surfaced paper passes over a roller. Other loose particles are blown off by a fan, while the remaining ones are still more firmly fixed by a second jet of steam.
♦Cork♦
Cork-paper, an American invention, is made by coating one side of a thick, soft and flexible paper with a preparation of glue, gelatine, and molasses, and covering it with finely ground cork lightly rolled in. This paper is used for packing bottles, glassware, etc.