Sec. II. Of Priming and Whitening Cases, and Remarks concerning Spunk and Touch Paper.
When the cases are charged, we pierce them with a small awl, or make a hole with a gimblet in the end, if it should be stopped with clay, or probe them with a drill, as fire-workers call it, in the hole which had been filled, in which we put some more of the composition. This precaution is considered necessary, in order that the earth should not cover internally the hole of the piercer. A piece of match is then introduced, which extends on the outside, and is secured there with a plug of wood.
Brown paper, made either of linen or cotton, but not of woollen cloth, when soaked in a concentrated solution of saltpetre, is, we have said, rendered very combustible, and will convey fire for small works with much facility. It is this paper, called touch, or more properly match, paper, that is used for capping, &c. Paper of this kind may sometimes be used, as for crackers, serpents, &c. Cotton quick-match, however, is used more generally; and, for large works, when employed as a leader, it is usually confined in a proper tube, the better to preserve it entire, and to keep it dry. Spunk, made by soaking certain species of fungus in a solution of saltpetre, takes fire very readily by the least spark, and, therefore, is used for collecting and preserving the fire from flint and steel. This spunk, when well made, and particularly of the proper kind of fungus, may be cut into slips, and employed advantageously in some fire-works. In all cases, however, the object is the same, to communicate fire with facility to the powder, or composition; and this object may be attained by all those methods, which we have had occasion frequently to mention. See [Pyrotechnical Sponge.]
To whiten cases is an operation, which merely consists in covering them with paper, and is performed in the following manner. We procure as many half-sheets of paper as we have cases, and put them on a table one upon another. We paste the paper, and roll each case in one of these sheets, which is named the covering. The paper is cut in such a manner, that it passes over the end of each case an inch and a half. There is no particular use in this covering, the case being made sufficiently strong without it; it makes, however, a handsome finish. In the Chinese fire-works, their cases are covered with different coloured papers, and frequently ornamented with gilding. In all that I have seen, with some of which I have made experiments, the match of communication is nothing more than twisted match-paper. The figures are made of paper, painted, and ornamented in the same way; some resembling animals, &c. but on a small scale. The leaders are fixed in the usual manner, and the works are fired in the same way. Tourbillons, serpents, and crackers are chiefly the kind which we have seen.
The composition for producing this fire, as it is peculiar, and therefore distinct from all others, was invented by the Chinese, and hence bears that name. The substance, which produces the peculiar effect is cast or crude iron. See [Iron.]
It was the brilliant light, produced when iron filings are thrown into the fire, that gave rise to an improvement in the fire of rockets, rendering it much more beautiful, than when gunpowder, or the substances of which it is composed, are alone employed. The Chinese have long been in possession of a method of rendering fire brilliant, and variegated in its colours. Cast-iron, reduced to a powder more or less fine, is called iron-sand, because it answers to the name given to it by the Chinese. They use old iron pots, which they pulverize, till the grains are not larger than radish seed; and these they separate into sizes or numbers, for particular purposes.
It should be observed, that rockets, into the composition of which, iron-filings and iron-sand enter, cannot be long preserved, owing to the change which the iron undergoes in consequence of moisture.
It may be proper to introduce here two tables, which exhibit the proportions of the different ingredients for rockets of this kind from 12 to 33 lbs.
For Red Chinese Fire.