Page:Pyrotechnics the history and art of firework making (1922).djvu/146

 a short metal tube, which fits exactly a short metal plunger provided with a knob for the hand, and a small metal stud at the side. The tube has a slot cut partially down the side to receive this stud.

The method of using the pump is as follows:—The plunger is drawn up so that the stud rests on the top of the tube. The pump is pressed into a heap of prepared composition, which action has the effect of compressing the composition in the tube. The plunger is then turned so that the stud engages with the slot, and pushed down, forcing the star out of the tube. The composition is prepared for pumping by being damped with methylated spirit or some other suitable solvent, and after making, the stars are dried in specially constructed buildings.

Pinched stars are made by pinching the damped composition into a short paper case, through which a short length of match is first passed.

Charged stars have generally a clay or cardboard bottom to the case, and are usually matched. This form is generally used for Government signal rockets, as the composition being only at one end of the case, the time of burning is extended.

The mixing of compositions requires great care and thoroughness. Care both on account of the necessity of exact adherence to the formula, and to preclude the presence of any foreign body or chemical which, apart from any effect it might have on the successful functioning of the fireworks for which it happens to be used, might render it most dangerous in manipulation.

Generally working buildings are licensed for mixing compositions, but it is usual to set certain sheds apart for this purpose, especially if the chemicals used are of a dusty nature, that is, very finely divided, in which case the atmosphere becomes highly charged and dangerous.