Читать книгу The Pyrotechnist's Treasury; Or, Complete Art of Making Fireworks - Thomas Kentish - Страница 15

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No species of fireworks require greater care in their construction than roman candles. In the first place the stars must be fierce, that they may light thoroughly: next, they must not be driven out with too great velocity. For this purpose the blowing-powder must be carefully adjusted. The stars, also, must be of so easy a fit that when put into the case they may fall to the proper depth of their own accord. If they require pushing, they are too tight, and will probably be blown out blind. When made as directed they will, necessarily, be of an easy fit, as they will be of the inner diameter of the brass tube, while the bore of the case is equal to its external diameter.

To regulate the blowing powder, prepare a number of little scoops, like fig. 5, which is about the right size for the bottom star. They are formed of pieces of tin, zinc, or copper. Cut a long strip of tin, ¹⁄₂ an inch broad; cut this across into 7 pieces, of the following lengths, 1⁵⁄₈, 1⁶⁄₈, 1⁷⁄₈, 2, 2¹⁄₈, 2³⁄₈ and 4 inches. Round off the corners. Take a piece of brass wire, or stair-rod, about ¹⁄₄ inch diameter, and with the wooden mallet, before mentioned, fig. 26, bend each of the pieces round the rod into a half cylinder, or gutter. Take up the smallest, and hold ⁵⁄₈ of an inch of the end of the stair-rod in the end of the semicylinder, to keep it open; put the other part from a to b, fig. 5, in a vice, and pinch it up; it will assume the form represented; the bowl part will be ⁵⁄₈ long, and the handle 1 inch long. Make the bowl of the next scoop ⁶⁄₈ of an inch long, the next ⁷⁄₈, and so on; the handle will always be 1 inch long. The last, for the top star, will have a bowl of 3 inches. The smallest scoop ought to hold as much grain powder as will weigh about ¹⁄₁₂ of the star; but to have the scoops accurate, it will be necessary to charge a roman candle, fire it, and observe whether the stars go a uniform height. For measuring the interval fuse, or fuse between the top of one star and the bottom of the next, a large scoop of the size of fig. 10 will be required. The tin may be an inch broad, and the bowl part 2¹⁄₂ inches long, bent round the rammer, fig. 4. To adjust it, take a roman candle case, fit it on the foot, fig. 9, which is a piece of wood, or brass, turned with a tenon to fit tight in the bottom of the case. Fill the scoop, and strike it level, with a straight-edge; empty it into the case, rest the foot on a flat surface; insert the rammer, fig. 4, and jolt it up and down, a dozen times, or more, lifting it about ¹⁄₂ an inch at a time; put in another scoopful, and jolt it in like manner. If the 2 scoopfuls, thus compressed, fill an inch of the case, the scoop will be correct. If more or less, the scoop must be shortened, or lengthened, accordingly.

A piece of writing-paper may be pasted and wound twice round the handle of each scoop, as from a to b, fig. 4. One dot can be put upon the scoop, for the first, or bottom, star; two dots, for the second scoop, &c., or any memorandum can be written upon them, for future guidance. Should they get soiled, they may be cleaned with a soaped damp piece of sponge.

Gunpowder, for fireworks, is used in two forms; meal-powder, and grain-powder. Meal-powder is a fine black dust, and is employed in all cases of mixing. Grain-powder is of three kinds, F, FF, and FFF, fine, double fine, and treble fine. FFF is best for crackers, simply because it runs rapidly down the pipes: for driving stars, shells, &c., F will be sufficient; but FFF may be employed: FF need not be purchased. All kinds of powder may be obtained of Pinnell, 214, Whitechapel Road. If, in any place, there should be a difficulty in obtaining meal-powder, F grain-powder may be crushed in a leather bag, by laying the bag on a hard surface, and beating it with a hammer. The leather should be of the same kind as shoes are made of.