Of the Moulds, Ra71271107'S, and other Utensils required in making Fireworks.
Many of these utensils require to be made with such accuracy, while their forms and_ materials are not at the same time obvious, that a description of them is absolutely necessary. Without great care in the form and workmanship, and in the choice of substances for many of these tools, the work becomes difficult, or te dious, or impossible; or, if it is executed with much unnecessary labour, the performance of the fireworks is incorrect, or sometimes even fails altogether. In de scribing these objects we shall pass slightly over those which are most easily made, for the purpose of explain ing more particularly the nature and construction of those that require greater nicety and more care.
The fundamental utensil, in every sense of the word, required in making fireworks, is a stout block of wood cut across the tree, such as that used by butchers for chopping blocks. Plate CCCCLXX1I. Fig. 1. More than one of these will of course be wanted, either where there is much work to be done, or many sizes of cases required. It is very convenient to have cavities sunk in those blocks, fitted to contain the bottoms of the moulds, to be afterwards described, by which means they are the more easily kept steady in driving.
The mallet required for driving is made of beech, of a cylindrical form, with a handle prolonged from the axis of the cylinder, having a knob or projection at the end to prevent it from slipping out of the hand. One side of the cylinder should be shaved off for the sake of obtaining a flat surface. Different sizes are also required for different kinds of work ; as, with the heavy ones, it would be as impossible to drive small cases, as it would be to drive large cases with light mallets. None, however, need be less than half pound in weight, and the largest need not exceed six pounds. A series consisting of half a pound, two pounds, four, and six, is quite sufficient.
Such are the materials required for driving. But it is not necessary that all fireworks should be driven by the blows of a mallet, and there are indeed many that will not admit of it. In the smallest classes of serpents and lights, for example, it is more convenient and quicker to drive without the mallet. As a substitute, a metallic ramrod may be adopted ; and by making the head sufficiently heavy, as much force as is required may be given with more convenience, while the work also proceeds very quickly. These rammers are best
made of gun metal; and it is necessary that they should be very smooth and true. The sizes most be propor tioned to those of the former and wooden ramtners, hereafter to be described.
The Former. Only two shapes for these are requir ed, namely, spherical and cylindrical. The first, how ever, are only wanted for the construction of paper shells for mortars: the latter belong to all other fireworks of whatever nature. One, or at most two sizes are sufficient for the spherical lormers, and their diameters may be computed for a coehorn, or 52 inch mortar, and for an 8 inch one, as it is not convenient to throw larger shells, on account of the weight and size of the mortar, and as the difference between the royal and coehorn mortars, which is only an inch, renders it unnecessary to adopt both.
As the thickness of the shell for the 8 inch diame ter cannot well be less than an inch when complet ed for firing, six inches will be the diameter of the spherical former for this class of mortars. For the coehorn shell ths of an inch is a sufficient thickness; and the former for this size will therefore be q inches. These spheres are to be made of beech, and they must be turned very true and polished. A hole is also to be bored in them of an inch in diameter, to receive the stand on which they must be placed when used, and by which also the fuse hole is deter mined.
The cylindrical formers require to be of every dia meter that may be wanted, from the sixth of au inch up to six inches, or even to a foot; as there is no limit to the sizes of fireworks, either for number or dimen sions, but the fancy of the operator. The best wood for them, where they are made of wood, is beech ; and it is most necessary that they should be turned very truc in the lathe, as, if they are not regularly cylindri cal, it will be difficult to withdraw them from the wet cases. For the same reason they should also be wrought or polished to a smooth surface. At one end they are provided with a head, or enlargement, to render them easier to hold in the hand. The length is a matter of indifference when they arc made, as they can be cut down at any time to be fitted to the rammers and moulds; and when they arc thus adapted, they ought to exceed the lengths of the moulds by two or three inches. More than that is not necessary.