CHAPTER I

SIMPLE FIREWORKS—ROCKET CLASS

In the preceding chapters we have been dealing with displays of fireworks, that is to say; fireworks in the mass. We will now turn our attention to the firework units composing those displays, and endeavour to trace their gradual evolution from the crude originals.

Fireworks may be divided into two classes, simple and compound. The first of these include fireworks which are a complete item in themselves, as the rocket, shell, or Roman candle; also the units which, fitted on a framework, go to compose the set pieces and devices of a display, and the small shop goods not used in displays. We will consider this class first.

The two oldest forms of fireworks known are undoubtedly the cracker and the rocket. As we have already noted, both of these—or at least primitive forms—are mentioned by Marcus Graecus, Albertus, and Roger Bacon. The description by the former is sufficiently clear to leave no doubt in our minds that he is describing a rocket; although the description of a cracker is not so explicit as to enable us to say that he is actually describing a jumping cracker, yet his mention of folding and tying would certainly give colour to that belief. In fact, some writers have endeavoured to find a connection between the words “Graecus” and “Cracker.”

Greene, in “Orlando Furioso” (1599), uses the words, “Yes, yes, with squibs and crackers brauly.” John Bate, in his book previously mentioned, under the somewhat misleading heading, “How to make Crackers,” says: “It is well knowne that every boy can make these, therefore I think it will be but labor lost, to bestow time to describe their making.”

He also describes a kind of kite which he designates a “Fire Drake,” to the tail of which he fastens “divers crackers” which are shown in the illustration to be exactly like the jumping crackers of the present day. Babington illustrates a cracker fixed to the top of a rocket.

Pepys makes the following entry in his diary for November 5th, 1661: “Seeing the boys in the streets flying their crackers.”

The only practical difference between the cracker of 1635 and that of to-day is in the difference of methods of manufacture, the early practice being to fold the gunpowder in the paper, the modern, to roll a paper case and fill the powder in through a funnel, afterwards flattening it through a roller mill.

Curiously enough, although the cracker has been in use for centuries in England, there appears to be no early reference to it on the Continent, the word “petard” meaning a cracker in French, but more often being applied to a firework with a single report, such as a maroon or cannon. The _Dictionnaire National_ of 1852, however, describes the true cracker as one of the meanings of “petard.”

The rocket is equal to the cracker in its claim to antiquity, and it is extraordinary that these two fireworks should have changed so little in form and composition.

John Babington gives illustrations of rocket-charging tools and describes the manufacture of rockets, which are approximately those of the present day. It is only in the proportion of the ingredients that there is any considerable alteration.

The word “rocket” appears to be Italian in origin, and to be based on the similarity in appearance of a rocket on its stick to the round piece of wood used in the Middle Ages to cover the point of a lance in mimic combat, and known as a “rockette,” from “rocca,” the Italian word for a bobbin, a diminutive of distaff.

As a rocket is the most important unit in the art of pyrotechny, a description of its manufacture will assist in the consideration of a large number of other fireworks which are either modifications of or based upon the underlying principles of the rocket, as well as the several principles governing all fireworks.

The ingredients of rocket composition are those of gunpowder in approximately similar proportions, but the resultant composition is not gunpowder, the reason being that the ingredients are less intimately mixed, with the result that the combustion is spread over a longer interval of time. Instead of the whole mass deflagrating instantly, only the exposed surface is consumed. It is the recoil produced by the rush of gases, and partially consumed matter, from the violently burning composition which projects the rocket forward. The obvious form for the case containing the composition is cylindrical, both on account of ease of construction and of charging. In order to get the greatest possible reaction from the burning composition, the case of the rocket is constricted or choked, so that the fire may issue as it were in the form of a jet. This choke has one obvious disadvantage, it reduces the surface of composition to the area of the opening, thus restricting the initial burning surface at the time when the maximum of effort is required to force the rocket into motion. This defect is overcome by having a tapering hole up almost the entire length of the composition, thus giving a large burning surface with a consequent discharge of gas through a small orifice and a resultant powerful jet of fire and gas.

The rocket case is of stout paper rolled on a former consolidated by rolling under a board. The choke is formed by inserting into the bore of the rocket two wooden tools with rounded ends, the shorter tool having a peg projecting which is equal in diameter to the bore of the choke. The tools are of such length that when they are inserted the peg takes up the position where the choke is to be formed. The case is then constricted at this point by a strong pressure with a stout cord wound round the case and soaped to allow it to slip round easily.

The case is then dried and charged by placing on a “spindle,” which is a strong gun-metal base with a nipple fitting into the vent of the rocket and having a tapering spindle which fits tightly in the choke and projects up into the bore of the rocket. The composition is poured in in small quantities measured in a scoop, each scoopful being consolidated by blows with a wooden mallet or a wooden “drift” hollowed to take the spindle. Before the first scoop of composition is introduced, the rocket is “set down,” that is, several blows are given on the drift to consolidate the paper at the choke and give it accurate shape. Next, a scoop of ground dry clay is poured in and charged firm as a protection to the paper of the choke. The charging is then proceeded with as detailed above. Varying drifts are used in order that the hole may approximately correspond with the diameter of the tapering spindle as the composition rises in the case.

A short portion of the case above the spindle is charged solid; this is referred to as the “heading,” and is usually about one and a half times the bore in depth.

Large rockets are charged in a mould which fits tightly round the outside of the case and prevents the case being split under the pressure of the blows whilst being charged.

In early times these moulds were used for all sizes and were of cast metal, and it is from them that the classification of the sizes is derived. Rockets are designated by the weight of a ball of lead which fits the bore of the corresponding mould. Thus we have rockets varying in size from ½ oz. to 6 lbs. and over, war rockets being made up to 9 and 24 lbs., but their use is now almost extinct.

This classification, although it serves its purpose well enough, is somewhat misleading, as the thickness of the case varies in practice, at any rate under modern conditions. In the seventeenth and eighteenth centuries pyrotechnists seem to have had a standard proportion between the case and bore, _i.e._, the thickness of the case was one-quarter the internal diameter of the rocket.

In modern commercial practice a rocket—say for example of 1 lb.—is a rocket rolled on a former whose diameter is that of the bore of a 1 lb. rocket of standard thickness, but whose outside diameter is governed by the strength of the paper employed in the case.

Several writers on pyrotechny, one Frézier writing in 1747 in particular, have endeavoured to supersede this classification of rockets by replacing it with a series of internal diameter measurements, so far without success. It is hard to supersede the traditions of centuries on a plea of mere rationalism.

Rocket compositions, although containing the same ingredients, namely, saltpetre, sulphur, and charcoal, have them in differing proportions. Broadly speaking, the larger the rocket the greater the proportion of charcoal and sulphur, the variations in proportion being considerable, from the half-ounce rocket mixing of 13 saltpetre, 2 sulphur, and 5 charcoal to the 9 lb. and 24 lb. war rocket, with 13 saltpetre, 3 sulphur, and 4 charcoal approximately, and even higher proportions of the second and third ingredients for special purposes. A larger proportion of charcoal gives a larger tail—a desirable feature in display and signal rockets. Some compositions have a proportion of mealed gunpowder to produce fiercer burning.

Early makers appear to have used mealed gunpowder and added charcoal and other ingredients to, as it were, dilute the powder and render the deflagration less fierce. Babington (1635) adds charcoal in the following proportion:

1 oz.—4 oz. rockets, 1 lb. of mealed powder to 2 oz. charcoal 4 oz.—10 oz. „ 1 lb. „ „ 2½ oz. „ 10 oz.—1 lb. „ 1 lb. „ „ 3 oz. „

John Bate’s compositions are rather erratically arranged; in some cases he adds the saltpetre, charcoal, and sulphur, and a further addition is “yron scales,” presumably to increase the effect of the tail, for which purpose later pyrotechnists used iron filings.

The rocket having been charged to the top of the heading, clay is charged in, forming a diaphragm above it. Earlier practice was to turn down the top edge of the case on the heading composition to form a diaphragm.

The best-known form of rocket is the sky rocket, which is fitted with a stick held in position by having a dowelled end introduced into a rolled paper or metal tube secured to the side of the rocket. The object of the stick is to direct the flight of the rocket, and further serves to hold it in position for firing, being passed through two rings at a suitable distance one above the other on a stake, through which it slides easily.

Sky rockets are fitted with a “cap” containing the “garniture” of the rocket, which may take the form of “stars” or other pyrotechnic effects, or a gun-cotton wad, or similar explosive to make a sound signal, or small cases charged with picrate of potash, producing the well-known “whistling rocket” effect.

The “cap” is either cylindrical or in the form of a truncated cone, with a conical or other top. The cap is burst open and the contents ignited by an opening charge of powder lighted through a hole bored in the clay diaphragm above the heading, so that when the heading is burnt through the fire may be communicated to the opening charge.

From earliest times the rocket has been the chief item in recreative fireworks; either the sky rocket as we know it to-day or its many modifications and derivatives was the chief constituent of the early displays.

During the sixteenth and seventeenth centuries a display would contain the following items—dragons or similar figures issuing from the scenic castle provided for the display; these would be moved by line rockets. A line rocket has no cap or garniture, the socket usually provided to hold the stick being lengthened, and of sufficient diameter to allow it to slide along a tightly stretched cord passed through it. Pieces of a similar nature to the modern fountain and gerb would be represented by “ground rockets.” This is a rocket less fiercely burning, charged solid, fixed to a support so that it remains stationary whilst burning, the fire being thrown out in a jet. Rockets would also be used to turn such primitive wheels as were exhibited, and to actuate mechanical scenic devices, which are in effect the “turning cases” of the present day. Serpents of fiz-gigs were much used, both as a garniture for rockets, and to give animation to wheels and similar pieces. These were made on the rocket principle, similar to the squib, but slightly more elaborate. A choke was formed between the composition and the “bounce” or powder giving the report.

To-day the ground rocket has developed into the gerb or Chinese tree, fountains of various kinds, the flower pot—of the larger kinds; and among the smaller varieties, the squib with its variations, such as Black Jack and Blue Devil, and the golden rain with its variations.

The modern, or rather more recent, method of heading the rocket with a clay diaphragm evidently suggested that the choking of the case might be dispensed with where the composition was less fierce, the necessary reduction of the orifice being produced by a clay diaphragm with a central hole of sufficient size. This method is followed with the gerb, fountains, and flower pot, and in the firework known to pyrotechnists as “fixt”; this unit is largely used in display work to form the fringe frame or lattice effect of a set piece. “Fixt” are made in 1 oz. and 2 oz. sizes, and contain a composition of approximately one part of steel filings to four of mealed gunpowder and finish with a bounce. The origin of the name is uncertain: it may refer to their use on fixed pieces in contradistinction to one revolving, or—as is most probable—was first used to distinguish between a fixed and a moving rocket.

The time of the introduction of the clay choke is uncertain. Jones, writing in 1765, although using clay in the heading of rockets, still choked all cases, but Mortimer (1824) uses it, although Ruggieri (1821), whilst doing the same, appears to think choking preferable.

The former gives instructions for charging the clay solid and boring the central hole; Ruggieri, however, uses a nipple like a much shortened rocket spindle, in which he agrees with the modern practice. This method is also utilised at the present time for small-sized rockets.

Of the fireworks of the fountain class, probably the first to develop from the crude rocket form were the gerb and flower pot. The gerb, or Chinese tree, contains a composition of saltpetre, sulphur, charcoal and iron borings, with the addition—if more force is required, as for instance to turn a device—of mealed gunpowder. Early makers used mealed powder alone and “iron sand,” or cast-iron reduced to powder by hammering. This composition is known as Chinese fire, and, as its name implies, was introduced into Europe from the East. An interesting article appeared in the “Universal Magazine” of 1764, written by a Jesuit missionary on the subject of Chinese fireworks. In it he describes the making of iron sand as follows:

“Old broken or useless pots serve generally for making this sand; they are broken into pieces of the breadth of the hand, after which, being made red-hot in the fire of a forge, they are thrown in that condition into a trough filled with fresh water, where they are left to cool. Thus calcined, the rust falls off in scales, and they are easily reduced into sand, being first broken into parcels of a finger’s breadth. The anvil and hammer used for this purpose must be also of cast-iron, because steel flats the grains of sand. It is necessary that the angles of those grains should be sharp, as it is the angles that form the flowers.”

The word “gerb” is derived from the French word meaning a sheaf of corn, and was first applied to water fountains.

The flower pot is charged with a composition formerly known as “spur-fire,” from the resemblance in form of its coruscations to the rowel of a spur. The effect produced is one of the most effective when successful, but has the disadvantage for display work that the effect is only appreciated at close quarters. The ingredients used are lampblack, sulphur, red arsenic, saltpetre, with sometimes the addition of charcoal and mealed gunpowder.

Of the smaller works of this division the squib and golden rain are too well known to need description. The squib and its variations have a choked case; the golden rain and similar works are left with an open bore.

Squibs are generally filled with a composition of sulphur, saltpetre and charcoal, sometimes steel filings, with a bounce of fine-grain powder.

A curious firework, now almost obsolete, for which it is difficult to find a class, is the five-pointed star. This work consisted of a case having a diaphragm of plaster of paris or clay above the filling, below which five holes are bored equidistant and at right angles to the axis. The case is fired in the unusual position of horizontal with the end towards the spectator, the fire playing all round the case, forming a star. The composition used was mealed powder, sulphur, saltpetre, and sulphuret of antimony. Ruggieri mentions this firework under the name “Etoile fixé,” and it is mentioned by Jones, writing in 1765, but not by Frézier.

It is hard to believe that this unit was successful, so many factors militating against success, which depends upon the exactly similar jet from each of the five holes. But it is possible that in large geometrical pieces it was at least of use to give an additional effect in what, owing to the lack of variety of the fireworks of the time, must have been rather a monotonous repetition of a few effects. It also would enable small blank spaces to be filled in on set pieces. In a sun or star of the ordinary type, that is of radiating cases, the commencement of the jets must be as far apart as the length of two of the cases, which length is governed by the required time of burning. This leaves a blank centre; the five-pointed star, however, if working correctly, has the jets radiating from a point.

Many of the earlier writers classified fireworks under the heads:—Fireworks for the ground, for the air, and for the water. Those falling in the latter division are only variations of those for the ground, that is to say, a gerb, fountain or other firework is fitted with a float, such as a block of wood, and functions floating on the surface of the water, the effect being greatly enhanced by the reflection.

It is not proposed to deal separately in this work with aquatic fireworks unless they have some essential difference from their parallel type for land display.

One unit, of the rocket class, which is so distinct is the “skimmer.” This is in effect a stickless rocket with the cap (which is empty) fastened at an angle to the line of the main case. When fired the skimmer, as its name implies, skims over the surface of the water, with occasional dives under the surface in an erratic course. It requires for its safe display a considerable area of water. These are known by French pyrotechnists as “genouillères,” from their shape.

Ruggieri and Frézier describe what they call “plongeons.” These are gerbs charged in the ordinary way, except that before each scoop of composition a small quantity of mealed powder is added. This produces a jerky burning, the recoil of each puff of powder driving the gerb beneath the surface of the water; the jet of fire, of course, is sufficient to prevent water entering the case while so submerged. These, and other earlier writers, in their section devoted to aquatic fireworks, give directions for firing ordinary land fireworks on the water, which would almost appear to have been included with the idea of filling space. One item which is generally included consists of directions for firing rockets under water. Jones, under this heading, gives the following directions:

“TO FIRE SKY ROCKETS UNDER WATER.

“You must have stands made as usual, only the rails must be placed flat, instead of edgeways, and have holes in them for the rocket sticks to go through; for if they were hung upon hooks, the motion of the water would throw them off: the stands being made, if the pond is deep enough, sink them at the sides so deep that when the rockets are in their heads may just appear above the surface of the water; to the mouth of each rocket fix a leader which put through the hole with the stick; then a little above the water must be a board, supported by the stand, and placed along one side of the rockets; then the ends of the leaders are turned up through holes made in this board, exactly opposite the rockets. By this means you may fire them singly, or all at once. Rockets may be fired by this method, in the middle of a pond, by a Neptune, a swan, a water-wheel, or anything else you chuse.”

It will be seen that the rockets themselves are above the surface, which seems more reasonable than the instructions of some writers, who, to get the effect of a rocket rising from actually beneath the surface, give themselves an infinite amount of trouble to render the case and connections waterproof. The effect seen from a short distance is identical.