Pasteboard is made in the following way: A paste of flour is first prepared with hot water, and passed through a hair sieve, to separate the lumps. A sheet of paper is stretched upon a table, and covered, by means of a brush, with paste, and a sheet is then laid over it. This is compressed, and another coat of paste applied; then another sheet, then paste, and the number is added according to the thickness required. After five or more sheets are thus pasted together, a dry sheet is laid over, and the operation is repeated, till five more are joined. Then a dry sheet is put on, and the pasting is renewed. By this means, every five sheets are joined together, and the sheet, thus formed, is kept apart from the rest, by the dry sheet. A pile of pasteboard, consisting of some hundred sheets, may be made in this manner at one time. They are then put into a press for the space of five or six hours, by which they become firmly united, and all the extraneous paste is pressed out. When a press cannot be had, they may be put between boards, and heavy weights laid on. The pasteboard is then hung up in the air to dry, and again submitted to the press, to remove any inequalities, and to make it smooth.
When glazed paper is used for making pasteboard, we may employ, alternately, a sheet of brown paper. It is better, however, to use more of the glazed paper, than of the brown paper. Pasteboard of three thicknesses will be sufficient for most purposes. It is this kind, which is used for the heads of rockets.
Several kinds of paper, however, are used in fire-works. For small preparations, common white paper is sufficient. For port-fire cases, the common brown paper; for the joints, guarding places from fire, and covering tubes of communication, any kind of gray paper; and for covering marrons, the most indifferent kind may be used. Cartridge paper, as known by that name, may be used for a variety of purposes.
Paper may be rendered incombustible, or nearly so, by soaking it repeatedly in a strong solution of alum. In the Literary Journal of 1785, of Petersburg, there is a discovery mentioned of a kind of pasteboard, which neither fire can consume, nor water soften. It appears that alumina, and its salt (alum) were used in this preparation.
In the Journal des Arts et Manufactures, tom. ii, p. 205, is an account of the manufacture of pasteboard at Malmedy; and in the Transactions of the Society of Stockholm for 1785, is a description of the process for making the Swedish stone paper, which resists equally fire and water. Stone paper is manufactured in France, (Dictionnaire de l'Industrie, article Carton), by taking two parts of martial earth, (ochre, for instance), and mixing them with one part of animal oil, and two parts of vegetable matter, previously made into a pulp. The British Repository of Arts contains several specifications of patents for the preparation of the same paper.
Although paper may be rendered very difficult of combustion by the process already mentioned, that of soaking it in a strong solution of alum, yet to make a paper completely indestructible by fire, it must be made of amianthus. The process for manufacturing paper with this mineral, was announced in the Gazette de France in 1778. Professor Carbury received a medal for the invention.
Incombustible paper, for cartridges, ought to have the property, not of inflaming, but of simply carbonizing, when exposed to heat. M. Brugnatelli (Bulletin des Neustin) recommends the paper to be prepared with silicated alkali, commonly called the liquor of flints. Muriate of potassa, and supersulphate of alumina-and-potassa are both used for a similar purpose.
Paper made according to Brugnatelli's process, is merely carbonized by fire, and reduced to powder.
M. Hermbstaedt (Bulletin des Découvertes,) observes, that paper, made with silicated liquor, attracts humidity, and proposes simply a solution of green vitriol, which has not that property.
Paper may be stained, or coloured, in a variety of ways, as is the case with the portable Chinese fire-works, that are brought to this country. Thus, a red paper may be formed by dipping it in a decoction of brazil wood and alum; yellow, by using fustic; a green, by a mixed bath of blue and yellow dye, or a solution of copper, &c. Coloured paper may be glazed with weak size, rubbing it afterwards with a polished stone.