a chemical preparation, which has the singular property of taking fire as soon as it is exposed to the air. See Chemistry, no. 485.

PYROTECHNY;

The art of fire, or a science which teaches the management and application of fire in several operations. See Fire, Furnace, Chemistry, Distillation, Metallurgy, &c.

But the term is more particularly used to denote the doctrine of artificial fire-works and fire-arms, teaching the structure and use, 1. Of those used in war, the attacking of fortifications, &c. for which see the articles Gun, Gunnery, Gun-Powder, Fuses, &c. and Mine in the Appendix; and, 2. Of those made for amusement's sake, as rockets, stars, serpents, &c. the preparation and construction of which fall to be explained in the present article.

Sect. I. Of Ingredients and Compositions.

1. Saltpetre.

Saltpetre being the principal ingredient in fire-works, and a volatile body, by reason of its aqueous and aerial parts, is easily rarified by fire; but not so soon when foul and gross, as when purified from its crude and earthy parts, which greatly retard its velocity: therefore, when any quantity of fireworks are to be made, it should be examined; for if it is not well cleansed, and of a good sort, your works will not have their proper effect; neither will it agree with the standing proportions of compositions. Therefore,

To refine it, put into a copper, or any other vessel, 100 lb. of rough nitre with 14 gallons of clean water; let it boil gently half an hour, and as it boils take off the scum; then stir it, and before it settles put it into your filtering bags, which must be hung on a rack, with glazed earthen pans under them, in which must be sticks laid across for the crystals to adhere to: it must stand in the pans two or three days to shoot; then take out the crystals and let them dry. The water that remains in the pans boil again an hour, and drain it into the pans as before, and the saltpetre will be quite clear and transparent: if not, it wants more refining; to do which proceed as usual, till it is well cleansed of all its earthy parts.

N.B. Those who do not choose to procure their saltpetre by the above method, may buy it ready done, which for fire-works in general will do.

To pulverise Saltpetre. Take a copper kettle, whose bottom must be spherical, and put into it 14 lb. of refined saltpetre, with 2 quarts or 5 pints of clean water: then put the kettle on a slow fire; and when the saltpetre is dissolved, if any impurities arise, skim them off, and keep constantly stirring with two large spatulas, till all the water exhales; and when done enough, it will appear like white sand, and as fine as flour; but if it should boil too fast, take the kettle off the fire, and set it on some wet sand, which will prevent the nitre from sticking to the kettle. When you have pulverised a quantity of saltpetre, be careful to keep it in a dry place.

To extract Saltpetre from damaged Gun-powder. Have some filtering bags, hung on a rack, with glazed earthen pans under them, in the same manner as those for refining saltpetre; then take any quantity of damaged powder, and put it into a copper, with as much clean water as will cover it: when it begins to boil, take off the scum; and after it has boiled a few minutes, stir it up: then take it out of the copper with a small hand kettle for that purpose, and put some into each bag, beginning at one end of the rack, so that by the time you have got to the last bag, the first will be ready for more. Continue thus, till all the bags are full: then take the liquor out of the pans; which boil and filter, as before, two or three times, till the water run quite clear, which you must let stand in the pans some time, and the saltpetre will appear at top. To get the saltpetre... Ingredients petre entirely out of the powder, take the water from that already extracted, to which add some fresh and the dregs of the powder that remain in the bags, and put them in a vessel, to stand as long as you please; and when you want to extract the nitre, you must proceed with this mixture as with the powder at first, by which means you will draw out all the saltpetre; but this process must be boiled longer than the first.

2. Sulphur, or Brimstone.

Sulphur is one of the principal ingredients in gunpowder, and almost in all compositions of fireworks; and therefore great care must be taken of its being good, and brought to the highest perfection. To know when sulphur is good, you are to observe that it is of a high yellow; and if, when held in one's hand, it crackles and bounces, it is a sign that it is fresh and good; but as the method of reducing brimstone to a powder is very troublesome, it is better to buy the flour ready made, which is done in large quantities, and in great perfection; tho' when a grand collection of fire-works are to be made, the strongest and best sulphur is the lump brimstone ground in the manner directed in art 8.

3. Charcoal.

Charcoal is a preservative by which the saltpetre and the brimstone are made into gunpowder, by preventing the sulphur from suffocating the strong and windy exhalation of the nitre. Charcoal for fire-works must always be soft and well burnt, which may be bought ready done.

4. Gun-powder.

See Gun-Powder in the order of the alphabet. To grind or meal it, is directed in art 8.

5. Camphor.

This may be had in the shops; and is of two kinds, differing in regard to the degree of their purity, and distinguished by the name of rough and refined. Refined camphor must be chosen of a perfectly clean white colour, very bright and pellucid, of the same smell and taste with the rough, but more acid and pungent. It is so volatile that merchants usually inclose it in linseed, that the viscoity of that grain may keep its particles together.

6. Benjamin.

This is a resin found of different sorts; and distinguished by their colours, viz. yellow, grey, and brown; but the best is that which is easy to break, and full of white spots. It is one of the ingredients in odoriferous fire-works, when reduced to a fine flour; which may be done by putting into a deep and narrow earthen pot 3 or 4 oz. of benjamin grossly pounded; cover the pot with paper, which tie very close round the edge; then set the pot on a slow fire, and once in an hour take off the paper, and you will find some flour sticking to it, which return again in the pot; this you must continue till the flour appears white and fine. There is also an oil of benjamin, which is sometimes drawn from the dregs of the flour; it affords a very good scent, and may be used in wet compositions.

7. Spar-fire.

This fire is the most beautiful and curious of any yet known; and was invented by the Chinese, but now is in greater perfection in England than in China. As it requires great trouble to make it to perfection, it will be necessary that beginners should have full instructions; therefore care should be taken that all the ingredients are of the best, that the lamp-black is not damp and clodded, that the saltpetre and brimstone are thoroughly refined. This composition is generally rammed in 1 or 2 oz. cafes about 5 or 6 inches long, but not drove very hard; and the cafes must have their concave stroke struck very smooth, and the choak or vent not quite so large as the usual proportion: this charge, when driven and kept a few months, will be much better than when rammed; and will not spoil, if kept dry, in many years.

As the beauty of this composition cannot be seen at so great a distance as brilliant fire, it has a better effect in a room than in the open air, and may be fired in a chamber without any danger: it is of so innocent a nature, that, though with an improper phrase, it may be called a cold fire; and so extraordinary is the fire produced from this composition, that, if well made, the sparks will not burn a handkerchief when held in the midst of them; you may hold them in your hand while burning, with as much safety as a candle; and if you put your hand within a foot of the mouth of the cafe, you will feel the sparks like drops of rain. When any of these spur-fires are fired singly, they are called artificial flower-pots; but some of them placed round a transparent pyramid of paper, and fired in a large room, make a very pretty appearance.

The composition consists of saltpetre 4 lb. 8 oz., sulphur 2 lb. and lamp-black 1 lb. 8 oz.; or, saltpetre 1 lb. sulphur ½ lb. and lamp-black 4 quarts. This composition is very difficult to mix. The saltpetre and brimstone must be first sifted together, and then put into a marble mortar, and the lamp-black with them, which you work down by degrees with a wooden pestle, till all the ingredients appear of one colour, which will be something greyish, but very near black; then drive a little into a cafe for trial, and fire it in a dark place; and if the sparks, which are called stars, or pinks, come out in clusters, and afterwards spread well without any other sparks, it is a sign of its being good, otherwise not; for if any drofy sparks appear, and the stars not full, it is then not mixed enough; but if the pinks are very small, and soon break, it is a sign that you have rubbed it too much.

This mixture, when rubbed too much, will be too fierce, and hardly show any stars; and, on the contrary, when not mixed enough, will be too weak, and throw out an obscure smoke, and lumps of drops, without any stars. The reason of this charge being called the spur fire, is because the sparks it yields have a great resemblance to the rowel of a spur, from whence it takes its name.

8. To meal Gun-powder, Brimstone, and Charcoal.

There have been many methods used to grind these ingredients to a powder for fire-works, such as large mortars and pestles made of ebony and other hard wood, and horizontal mills with brass barrels: but none have proved so effectual and speedy as the last invention, that of the mealing table, represented in fig. 1, made of elm, with a rim round its edge 4 or 5 inches high; and at the narrow end, A, is a slider that runs in a groove and forms part of the rim; so that when you have taken out of the table as much powder as you can with the copper shovel fig. 2, sweep all clean out at the slider A. When you are going to meal a quantity tity of powder, observe not to put too much in the table at once; but when you have put in a good proportion, take the muller fig. 3. and rub it till all the grains are broke; then scarce it in a lawn sieve that has a receiver and top to it; and that which does not pass through the sieve, return again to the table and grind it, till you have brought it all fine enough to go through the sieve. Brimstone and charcoal are ground in the same manner, only the muller must be made of ebony; for these ingredients being harder than powder, would stick in the grain of elm, and be difficult to grind: as brimstone is apt to stick and clog to the table, it will be best to keep one for that purpose, by which means you will always have your brimstone clean and well ground.

2d 8. To make Wheels and other works incumbrable.

It being necessary, when your works are new, to paint them of some dark colour; therefore, if, instead of which, you make use of the following composition, it will give them a good colour, and in a great measure prevent their taking fire so soon as if painted. Take brick dust, coal ashes, and iron filings, of each an equal quantity, and mix them with a double size, made hot. With this wash over your works, and when dry wash them over again; this will preserve the wood greatly against fire. Let the brick dust and ashes be beat to a fine powder.

9. To prepare Cast-iron for gerbes, white fountains, and Chinese fire.

Cast iron being of so hard a nature as not to be cut by a file, we are obliged to reduce it into grains, though somewhat difficult to perform; but if we consider what beautiful sparks this sort of iron yields, no pains should be spared to granulate such an essential material: to do which, get at an iron foundry some thin pieces of iron, such as generally run over the mould at the time of casting: then have a square block made of cast iron, and an iron square hammer about 4 lb weight; then, having covered the floor with cloth or something to catch the beatings, lay the thin pieces of iron on the block, and beat them with the hammer till reduced into small grains; which afterwards scarce with a very fine sieve, to separate the fine dust, which is sometimes used in small cases of brilliant fire, instead of steel dust; and when you have got out all the dust, sift what remains with a sieve a little larger, and so on with sieves of different sizes, till the iron passes through about the bigness of small bird-shot: your iron thus beat and sifted, put each fort into wooden boxes or oiled paper, to keep it from rusting. When you use it, observe the difference of its size, in proportion to the cases for which the charge is intended; for the coarse fort is only designed for very large gerbes of 6 or 8 lb.

10. Charges for Sky-rockets, &c.

Rockets of four ounces. Mealed powder 1 lb. 4 oz. saltpetre 4 oz. and charcoal 2 oz.

Rockets of eight ounces. I. Mealed powder 1 lb. saltpetre 4 oz. brimstone 3 oz. and charcoal 1½ oz. II. Meal-powder 1½ lb. and charcoal 4½ oz.

Rockets of one pound. Meal powder 2 lb. saltpetre 8 oz. brimstone 4 oz. charcoal 2 oz. and steel-filings 1½ oz.

Sky-rockets in general. I. Saltpetre 4 lb. brimstone 1 lb. and charcoal 1½ lb. II. Saltpetre 4 lb. brimstone 1½ lb. charcoal 1 lb. 12 oz. and meal-powder 2 oz.

Large sky-rockets. Saltpetre 4 lb. meal-powder 1 lb. and brimstone 1 lb.

Rockets of a middling size. I. Saltpetre 8 lb. sulphur 3 lb. meal-powder 3 lb. II. Saltpetre 3 lb. sulphur 2 lb. meal-powder 1 lb. charcoal 1 lb.

II. For Rocket Stars.

White stars. Meal-powder 4 oz. saltpetre 12 oz. sulphur vivum 6 oz. oil of spike 2 oz. and camphor 5 oz.

Blue flares. Meal-powder 8 oz. saltpetre 4, sulphur 2, spirits of wine 2, and oil of spike 2.

Coloured or variegated flares. Meal-powder 8 drams, saltpetre 4 oz. sulphur vivum 2, and camphor 2.

Brilliant flares. Saltpetre 3½ oz. sulphur 1½, and meal-powder 4, worked up with spirits of wine only.

Common flares. Saltpetre 1 lb. brimstone 4 oz. antimony 4½, glassflas ½, camphor ¼, and spirits of wine ¼.

Tailed flares. Meal-powder 3 oz. brimstone 2, saltpetre 1, and charcoal (coarsely ground) ½.

Drove flares. I. Saltpetre 3 lb. sulphur 1 lb. brais dust 12 oz. antimony 3. II. Saltpetre 1 lb. antimony 4 oz. and sulphur 8.

Fixed pointed flares. Saltpetre 8½ oz. sulphur 2, antimony 1 oz. 10 dr.

Stars of a fine colour. Sulphur 1 oz. meal-powder 1, saltpetre 1, camphor 4 dr. oil of turpentine 4 dr.

12. Rain.

Gold rain for sky-rockets. I. Saltpetre 1 lb. meal-powder 4 oz. sulphur 4, brais-dust 1, saw-dust 2½, and glaas-dust 6 dr. II. Meal-powder 12 oz. saltpetre 2, charcoal 4. III. Saltpetre 8 oz. brimstone 2, glaas-dust 1, antimony ¼, brais-dust ½, and saw-dust 12 dr.

Silver rain. I. Saltpetre 4 oz. sulphur, meal-powder, and antimony, of each 2 oz. sal prunella ½ oz. II. Saltpetre ½ lb. brimstone 2 oz. and charcoal 4. III. Saltpetre 1 lb. brimstone ½ lb. antimony 6 oz. IV. Saltpetre 4 oz. brimstone 1, powder 2, and steel-dust ½ oz.

13. Water Rockets.

I. Meal-powder 6 lb. saltpetre 4, brimstone 3, charcoal 5. II. Saltpetre 1 lb. brimstone 4½ oz. charcoal 6. III. Saltpetre 1 lb. brimstone 4 oz. charcoal 12. IV. Saltpetre 4 lb. brimstone 13 lb. charcoal 1 lb. 12 oz. V. Brimstone 2 lb. saltpetre 4 lb. and meal-powder 4. VI. Saltpetre 1 lb. meal-powder 4 oz. brimstone 8½, charcoal 2. VII. Meal-powder 1 lb. saltpetre 3, brimstone 1; sea-coal 1 oz. charcoal 8½, saw-dust ½, steel-dust ½, and coarse charcoal ½ oz. VIII. Meal powder 1½ lb. saltpetre 3, sulphur 1½, charcoal 12 oz. saw-dust 2.

Sinking charge for water-rockets. Meal-powder 8 oz. charcoal ¾ oz.

14. Of wheels.

Wheel cases from two ounces to four pound. I. Meal-powder 2 lb. saltpetre 4 oz. iron-filings 7. II. Meal-powder 2 lb. saltpetre 12 oz. sulphur 4, steel-dust 3. III. Meal-powder 4 lb. saltpetre 1 lb. brimstone 8 oz. charcoal 4½. IV. Meal-powder 8 oz. saltpetre 4, saw-dust Sect. I.