224 



PYROTECHNY. 



dients. 



Pyrotech- dust, of elaterium bark, which has no existence ; and 

 "y- of oil of roses, which, for a composition of this weight, 

 ^&*y*+S would probably cost a few hundred pounds. 



Method of Grinding the Ingredients. 



The ingredients which require grinding for fireworks, 

 are saltpetre, sulphur, charcoal, and gunpowder, and 

 each of these requires some notice. 



SALTPETRE. It is sometimes recommended in the 

 books of pyrotechny, to pulverize the salt by boiling 

 it down, and stirring it with a stick as it begins to be 

 deposited, in consequence of the evaporation of the 

 water. But it cannot be reduced to powder of suffi- 

 cient fineness in this manner, so that mechanical means 

 become indispensible. For artificers who work on a 

 large scale, the common cylinder mill, similar to that 

 used by tanners and druggists, is the most expeditious 

 engine; and the cylinder may be made of limestone 

 or of metals, than which none is preferable to cast 

 iron. On a smaller scale, a pestle and mortar may be 

 adopted, and as far as either nitre, sulphur, or charcoal 

 is concerned, both of these may be made of iron. 

 Saltpetre, when produced, can scarcely be passed 

 through a fine sieve, from its adhering together, and 

 therefore the artificer must ascertain its fineness by the 

 feel, or by examining it on a smooth board, on which it 

 is diffused thinly by means of a muller of another 

 board, furnished with a handle. It is very essential to 

 the correct performance of all fireworks, and particu- 

 larly of sky-rockets and illumination lights, that the 

 saltpetre should be rendered perfectly fine. It is per- 

 haps cheaper to purchase it in that state, when it can 

 be done, from the powder makers, or the grinders of 

 drugs. 



SULPHUR. This may be powdered in the same man- 

 ner, but it admits of being easily sifted through the 

 lawn sieve, which is also required for the charcoal and 

 the mealed powder. The flowers of sulphur are some- 

 what more expensive, but they require no grinding. 

 The operator must, however, recollect what we men- 

 tioned before, that they generally contain acid, or a 

 portion of oil of vitriol. Hence they should be well 

 washed, till the water is tasteless, with water ; or, what 

 is better, with a weak alkaline lye first, and with water 

 afterwards. 



CHARCOAL. The same machinery serves for pow- 

 dering charcoal, but it requires a different process in 

 sifting. One sieve should be formed of fine lawn, and 

 this finest dust is reserved for compositions that are re- 

 quired to be very accurate, and to give flame rather 

 than sparks. The remainder may be divided by coar- 

 ser sieves into two qualities or more, according to the 

 fancy of the operator, the largest fragments being re- 

 served for wide cases and big fires, and the smaller for 

 sparks in cascades or wheels, or other works, accord- 

 ing to their respective sizes. 



MEALED POWDER. It is scarcely safe to grind gun- 

 powder either in a mill or a mortar, unless both of 

 these be made of wood, which would of course require 

 separate machines. If it can be procured, it is much 

 preferable to purchase gunpowder dust from the mills, 

 as it is a mere prejudice among firework makers to 

 suppose that it is not so strong as powder that has been 

 mealed. If, however, this cannot be obtained, the 

 powder must be reduced to this state by the artificer 

 himself. A large mortar of elm, with a pestle of lig- 

 num -vitse, will answer this purpose ; but there is an 

 inconvenience in this machine, arising from the adhe- 



sion of the powder in hard lumps to the bottom of the Pyrotech- 

 pestle. It is a better and speedier plan to grind gun- "X- 

 powder by means of an iron shot of 18 or 24 pounds ^ -p "Y"""' ' 

 weight, rolled in a large wooden vessel, turned out of 

 some hard wood ; either beech or elm. What is called 

 the mealing table is also used for the same purpose. 

 This is, as the name expresses, a table made of smooth- 

 ed elm, surrounded with a margin, on which the pow- 

 der is placed. By means of a flat piece of lignum vitse, 

 or other hard wood, of about six inches square, and 

 furnished with a proper handle, the powder is easily 

 rubbed down. This method is, however, less safe than 

 the preceding ; because, if any sand were present, an 

 explosion might easily be produced. In all such cases, it 

 is most important that the tables, or vessels of any kind, 

 should be provided with close covers when not in use ; 

 nor should more than a pound be pulverized at a time. 

 All these operations should also be carried on, where 

 there is room, in tents, and not in houses of any kind ; 

 as there is, in such situations, much less mischief pro- 

 duced by accidental explosions. Further, no more 

 powder should at any time be at hand than is imme- 

 diately required ; and whatever is finished should be 

 removed without delay. Mealed powder must be care- 

 fully sifted from the grains that may remain, by means 

 of the lawn sieve. 



On the mixing of Compositions. 



This is a circumstance which requires considerable On the 

 care, as the accurate performance of sky-rockets, and mixing of 

 of many other fireworks depends very much upon it. c p m P si - 

 It is impossible to be too particular with regard to l " 

 these, if any regard is to be had to their accuracy, or 

 if they are intended for signals, or for long flights. In 

 all sorts of illumination and fixed lights, it is even more 

 necessary to be accurate in this respect. In these, the 

 perfection consists in their burning with a steady 

 light, in their all giving out the same size of flame, 

 and in all lasting the same time. Otherwise, as so 

 many are used together, and always disposed in various 

 figures, the effect of a firework is apt to be materially 

 injured or altogether spoiled. There are many other 

 alterations required in this case, but it is the accuracy 

 of mixture which is our present concern. 



Supposing that all the ingredients of any composition 

 are determined on, as much should be made at once as 

 is sufficient for all the fires, whatever these may be, 

 that are to be introduced together, or to form any one 

 piece. This is one of the methods of insuring accuracy 

 in time, and correctness in performance. All the com- 

 positions that consist of fine materials, such as nitre, 

 sulphur, charcoal, and mealed powder, may be mixed 

 for an indefinite time, because they cannot be over- 

 done. There are different methods of doing this, and 

 the one or the other may be chosen according to the 

 quantity of the materials or the scale on which the 

 operator is to work. 



On a large scale, the most speedy and effectual me- 

 thod is by a hopper contrived for this purpose. The 

 composition having been first mixed with the hands as 

 far as it can, is placed in this machine, which is pro- 

 vided with a long and square wooden tube, like a com- 

 mon house gutter, for conducting rain from the roofs. 

 Within this, and in a part of it which is inlayed for 

 that purpose, there is placed an axis, carrying four or 

 more light vanes of tin or of wood, so adapted to the 

 inside of this receptacle or tube, as to fit it easily, and 

 capable of revolving in a vertical direction. The axis 



