Page:Pyrotechnics the history and art of firework making (1922).djvu/225

 CHAPTER VII

FIREWORK COMPOSITIONS

It may have been remarked in the foregoing chapters that, although the ingredients composing the firework mixtures are given, generally the proportions are not.

The reason for this is two-fold: primarily, as we have seen in the chapter on rockets, the proportion of the ingredients of a firework varies in accordance with its size. So that to give the proportions of the compositions of any one type of firework would often require as many formulæ as there are sizes.

Secondly, and perhaps more importantly, the quality and purity of chemicals as supplied in bulk vary so enormously that a constant series of experiments has to be conducted in order to ascertain what modifications and adjustments are necessary in the formulæ to give the required standard of performance.

It is not meant to suggest that the impurities generally to be found in bulk supplies are necessarily harmful to pyrotechnic results. This is not so; salts give far better results in their natural or mineral form than do those prepared synthetically. As an example of this saltpetre may be cited. For pyrotechnic purposes the best obtainable is that from Bengal, yet an analysis of this would probably be found to be less pure than that synthetically prepared in Germany. But experiments have shown that samples of the latter, taken from the same cask, but in different parts, produce very distinctly varying results pyrotechnically.

Pyrotechny is an art, chemistry is a science, and although it is impossible to deny that the former is greatly indebted to