Wood, in fact, may be rendered incombustible by several processes, some of which we have given. Earl Stanhope, among others, made some interesting experiments on this subject.[23]
Having thus given some of the modes, usually adopted to render wood incombustible, or to prevent its taking fire so instantaneously, we purpose to add some remarks respecting the processes for colouring it. An excellent preservation against moisture, which communicates a colour at the same time, is formed of 12 lbs of rosin, 3 lbs of sulphur, and 12 pints of whale oil, melted and mixed with a sufficient quantity of red or yellow ochre, and applied by means of a brush. Pulverized black lead may be substituted for the ochre. Several coats of this mixture may be put on, allowing each coat to dry before another is applied. This composition is particularly well adapted for wheel work, &c. and for aquatic fire-works. Chaptal advises, for the same purpose, a mixture of equal parts of white turpentine, bees' wax, and maltha, or, in the place of maltha, coal tar. Wood, covered with three coats of this composition, and immersed for two years in water, was found to be quite dry. It would be well, however, to cover it with some of the preparation, to render wood incombustible.
With respect to the staining of wood of various colours, several preparations may be used. To communicate a green colour, a hot solution of acetate of copper may be used; or verdigris, alum, and vinegar, boiled together. A decoction of brazil wood, with alum and cream of tartar, will impart a red; indigo, dissolved in sulphuric acid, (liquid blue dye), a blue; a decoction of logwood, nut-galls, and copperas, a black; a solution of dragon's blood, or of alkanet wood, in turpentine, a mahogany colour, &c. The imitation of bronze on wood may be effected, by covering it first with isinglass size, then suffering it to dry, and putting on a coat of oil gold size, and covering it with bronze powder, a preparation sold for that purpose. A solution of aloes in spirits, which communicates a greenish-black, is a great preservative of wood against worms.
M. Ollivier (Archives des Découvertes, v, p. 386) has given a variety of recipes for imitating bronze, stone, &c. He recommends the following for the imitation of ancient bronze, which may be applied to wood-work. Melt together 150 lbs of fine sand, 170 lbs of lead ore, (Galena), and 30 lbs of manganese, and add one-sixth part of brass. This compound is then pulverized. It is applied on the usual ground.
Black earth, as it is called, made of green earth, oxide of manganese, oxide of iron, and oxide of copper, is also recommended for covering wood-work. The composition for imitation marble, is 1 part of green earth, 1/2 a part of sand, and 1/8th of a part of bol. armen. By adding 1/14th part of yellow burnt copper, the colour will approach to green. The same composition, with 1/16th part of copper, and 1/32d iron, will give a black.
Sec. VII. Of the formation of Rocket, and other Cases.
The cases for rockets, as a general rule, are to be made 61/2 times their exterior diameter in length; and all other cases, that are to be filled in moulds, must be as long as the moulds, within a half of the interior diameter. Rocket cases, from the smallest, to 4 or 6 pounds, are generally made of the strongest sort of cartridge paper, and rolled dry; but the large sort are made of pasted pasteboard. (See [observations on that subject.]) As it is very difficult to roll the ends of the cases quite even, the best way is to keep a pattern of the paper for the different kinds of cases. These patterns should be longer than the case they are designed for, and the number of sheets required should be marked, which will prevent any paper being cut to waste. Cut the paper of a proper size, and the last sheet for each case, with a slope at one end; so that when the cases are rolled, it may form a spiral line round the outside; and that this slope may always be the same, let the pattern be so formed for a constant guide. Before you begin to roll, fold down one end of the first sheet so far, as that the fold will go two or three times round the former; then, in the double edge, lay the former with its handle off the table, and after rolling two or three turns, lay the next sheet on that which is loose, and roll it all on.
The smoothing board, which is about twenty inches long, is now to be applied; and after rolling the paper three or four times, lay on, in the same manner, another sheet of paper, and smooth it in the same manner. This operation is to be repeated till the case is sufficiently thick. When the last sheet is rolled, we must observe, that the point of the slope is placed at the small end of the roller.
The case being made, the small end of the former is put in, to about one diameter of the end of the case, and the end piece is inserted within a little distance of the former. Then give the pinching cord one turn round the case, between the former and the end piece. At first, pull easy, and keep moving the case, which will make the neck smooth, and without large wrinkles. This operation is called by the French strangling, or choaking. When the cases are hard to choak, let each sheet of paper (except the first and last in that part where the neck is formed) be a little moistened with water. Immediately after you have struck the concave stroke, bind the neck of the case round with small twine, which must not be tied in a knot, but fastened with two or three hitches.