Part 3

3. Having now cleared our way of these necessary preliminaries, we may at once proceed to speak of the manufacture of ROCKETS; first, of what a rocket is, and then of how it is made. There is nothing like starting with a good distinct notion of what we have to make before we set to work to make it. It is said of a person who was asked by his friend to give him a logical definition of a house, that he at once replied that “_it was a thing with a chimney_;” which definition, being equally applicable to a moderator lamp and a steam-engine, can hardly be considered exhaustive in the case of a house; and, in like manner, if we start with the idea that a rocket is _a thing that goes up in the air_, we shall not have any very tangible model of rocket excellence before us as a guide in our work. It is, however, very true that some rockets which we see can only be properly and faithfully described as things which go up in the air, for they no more deserve the name of a rocket than does a child’s kite or a cock-sparrow, either of which would come equally well under the above definition. But let us see whether we can arrive at something a little more accurate. A rocket we will define as _a species of firework which, when properly fastened to a stick of a certain size and weight suspended with its mouth downwards, and ignited, ascends into the air by the force of its own combustion, rises majestically to its proper height, throwing out, from the beginning to the end of its course, a rich and uniform tail of sparks, and at the extreme range of its flight giving birth to a cluster of stars, or shower of fiery rains, or other decorations, as they are called, which should burn long enough to be well seen, and not disappear almost at the moment of their appearance_. This is what every rocket should be when fired; and let me beg of you not to stop short of attaining this excellence, for perseverance will give you experience, and with the aid of these two you need despair of nothing. When I had been puzzled and misled by all the books and information on the subject that I could procure, and had met with nothing but failure in all my attempts, I set myself to work to make my own experiments in a new direction, on the supposition that I understood, to a certain extent, the principle on which success depended. And well do I remember my delight at seeing a rocket of my own production scramble up into the air in a very undignified and disorderly manner, and there perform certain nervous evolutions which I will defy any pen to describe or pencil to depict. But although its performance was erratic and laughable, I had conquered; the key from that moment was in my own hands; and soon, after careful consideration and a few more experiments, I managed to produce a rocket of which I saw no reason to be ashamed.

I have stated above what appearance a good rocket should present to the eyes of a spectator when fired; I am now about to state what appearance it should present to its manufacturer before being fired—in fact, what it is that he has to make. _It is a strong cylindrical case, made of pasted brown paper and imperial board, contracted near one of its ends in order to form a narrow aperture, and filled with a certain composition in such a manner that a long narrow cavity is left in its centre, extending almost throughout its whole length._ This is what I shall call the rocket, for the ascending power lies solely in this part; the head, being an after-addition, will be spoken of it in its proper place, and not allowed to interfere here. In the annexed woodcut A A represents the exterior diameter of the case; B B, the interior diameter of the same; C C, the long cavity extending from the mouth up the centre of the composition, which cavity is called the “soul” of the rocket; D D D, the composition with which the remainder of the case is filled. The lower of the two C’s represents the mouth, or “choke” as it is called, at which all the combustion that goes on in the rocket has to find its vent. When a light is applied to the mouth of the rocket, the whole surface of the soul of the rocket is set on fire at once, and on this depends its power of ascent; for so large a quantity of fire having to make its escape through so narrow an aperture and meeting with considerable resistance from the external air, makes the rocket recoil in a direction opposite to that of its mouth, until all the combustible material which it contains is consumed. This is a broad outline of the principle upon which rockets ascend. It will be unnecessary for me to dive deeper into theories here, for I am sure that you will be anxious for me to come to practical details without further delay.

Among other things in my prefatory remarks I stated that firework-making need not be an expensive recreation, but you must bear in mind that nothing is easier than to make it expensive, and that we must adopt some strictly economical system of operation. Since rockets are the most scientific of all fireworks, and the apparatus necessary for making them is more costly than that for making any other kind of firework, we must do all that we can to bring their manufacture within reach of the amateur. There are many books, and I dare say many persons, that will tell you that you cannot hope to produce a good rocket unless you have a mould proper for the purpose made either of gun-metal or of some hard wood. I believe that I am right in telling you that such a piece of apparatus varies in cost from 3_l._ to 10_l._, but I also know that I am right in assuring you that a rocket, in every respect equal to many that are rammed in a mould, may be produced without this expensive luxury. I can only say that I _never_ use a mould, and my belief is that the workmen employed by professional pyrotechnists are, for the most part, only too glad to dispense with its use, for it is of importance to them to ram the greatest possible number of rockets in a given time, and if they were to be delayed by having to unscrew and screw a mould before and after filling each case, half their time and its value would be lost to them. I use, and recommend you also to use, a simple steel spindle let firmly into a wooden block, and if your cases are made strongly enough you will be able to produce all that your ambition will picture to you by means of this inexpensive apparatus, and without the help of the mould.

But before we speak of the size and proportions of this spindle it will, of course, be necessary for us to determine the size of the rocket which we intend to produce. Now, the rocket that I recommend you to make, as being the most generally useful and economical, is that which the professionals call the _¼lb. rocket_. You will bear in mind that this name is not intended to signify that the rocket when finished will weigh a quarter of a pound, but that its interior diameter is equal to the exterior diameter of a leaden ball weighing 4oz. You will find, I am sure, that the capabilities of this size of rocket, when properly made, will satisfy you for all ordinary purposes, and, taking this for granted, I shall now proceed to speak of this particular size only, in order to prevent the possibility of confusion.

ROCKET-CASES.

4. The first thing that you have to do is to make the case. Do not hurry over this part of the process, for more depends upon it than is generally supposed. It is made in the following manner:—Procure some imperial board (which is a kind of thin pasteboard made of two sheets of brown paper pasted and pressed together); also some stout Kentish brown paper of such a substance as will weigh 70-lb. per ream. Now fold a sheet of the imperial board down the middle of its length, thus:—

Cut it along this fold, then divide each of these halves crossways into five equal parts and cut them apart. Each sheet will thus furnish enough board for ten ¼lb. rocket-cases. This board is only made in one size. Now take a sheet of the 70-lb. brown paper, divide it into halves at its natural fold, and then divide each of these halves crossways into four strips. One of these, together with one of the strips of imperial board, will be sufficient to make one case. I have given you above the directions for cutting your paper and board without waste; you will, however, find it more convenient to buy them ready cut up; it will save you time and trouble, and will occupy much less space among your stores. They can be procured of Mr. W. H. Darby, 98, Regent Street, Lambeth, London, and he will supply them ready cut if you only state for what purpose they are intended.

The “former,” on which the board and the paper are to be rolled, is simply a piece of brass tubing, about 12 in. long, and ¾in. in diameter. This you had better procure of the person whose name I shall mention presently, when I speak of apparatus, and to whom I recommend you as a maker of all pyrotechnic _tools_, except such things as the sieves, &c., above mentioned.

I must not speak about the pasting and rolling of the cases until I have said a few words upon the subject of the paste itself. It is a great mistake to have your paste made thick; you will gain nothing by doing so, and you will find it very troublesome to use. It should be made of such a consistency as will admit of its being spread very readily upon the brown paper, &c., and by being tolerably fluid will saturate it much more thoroughly; and this, after all, is what you want to do, for the hardness of the finished cases depends far more upon the complete saturation of the paper than upon the thickness of the paste between its layers. The brush, which you will find convenient, is one about 2in. in diameter, and can be procured of Mr. Darby. Into each pint of paste, while boiling, put a large teaspoonful of powdered alum; this will have the effect of keeping your paste sweet and free from mouldiness for weeks, and will also prevent it from becoming watery, which it would otherwise do in a few days.

I will now suppose you to have your paper, imperial board, paste, and brush ready to hand. You will next require some kind of slab on which to paste and roll your cases. For this purpose I use one of the largest common roofing slates that can be procured: its size is 24 by 12in. This makes a cheap and very serviceable pasting slab if its surface be only moderately smooth.

Now we come to the actual rolling of the cases. First paste all over one side of one of the strips of 70-lb. brown paper; then take one of the strips of imperial board, and fold one end of it once round the brass tubular “former.” Hold this, thus folded, with your left hand, and paste over all the rest of the upper side of the strip with your right. Then roll it up, as straightly and as tightly as you can, till all but about 3 inches of it is wound upon the “former.” Upon these projecting 3 inches lay the end of the strip of brown paper, with its pasted side upwards, and then roll it till both board and paper are neatly and closely wound round the “former.” You will find at first a little difficulty in getting the strips to roll up straight, but a little practice will overcome this. You will now require what is called a “rolling board,” that is, a piece of common smooth deal board about 20 inches by 8 in size, with a wooden handle screwed on its upper side at one end (see fig. 3). Then with the left hand take hold of the end of the “former,” which projects out of the case, loosely, so as to allow it to revolve in the hand, and with the right hand roll case and “former” from one end of the slate slab to the other between it and the rolling board, pressing upon the latter, and using it as a carpenter does his “trying plane;” and by this means the same effect will be produced upon your newly-made case as is produced upon linen, &c., by a mangle. These directions read, no doubt, as if they belonged to some very complicated operation; but let me assure you that it is one far easier to perform than to describe. Some modification of this plan will in all probability suggest itself to your mind as an improvement upon it; for there are few people who do not after a few trials fall into some method of working which, besides answering their purpose, has the additional merit of being peculiar to themselves. I may as well mention here that the quickest way of making cases is to paste all your strips of paper and board before you begin to roll any of them, taking care not to paste that part of each strip of board which is to make the first turn round your “former.”

In the next place, when you have made as many cases as you require, the operation of “choking,” or forming their mouth and neck, remains to be done, and is to be accomplished in the following manner:—Procure some strong close string about one-eighth of an inch in diameter; take about one yard of this, and tie one end of it to a ring or nail which has been driven very tightly about 3 feet from the ground into a wall, beam, or tree, and the other end of this string tie firmly round a stout piece of stick or ruler about 18 inches long. Now take the round-ended drift (fig. 4), and insert this into one end of your cases till its rounded end appears about an inch from the other end, leaving, in fact, an inch at one end of the case unoccupied by the drift. Then take the little “choking piece” (fig. 5), and insert its metal point into the hollow end of the drift. This operation is illustrated at fig. 6. Now rub your string well over with yellow soap; the more thoroughly this is done the better. Then pass the stick or ruler between your legs in such a manner that by leaning backwards you can make the string very tight; but before tightening it give the soaped part of the string one turn round the part of the case marked _e e_ (fig. 6), then by leaning backwards you will contract that part of the case until you leave an aperture only large enough to admit the point of the “choking piece.” As soon as this is done tie some string tightly round the neck thus formed, to prevent its becoming larger. The best knot for this purpose is the one given at fig. 7. Then, when you have drawn out your choking piece and drift, the proper name of which latter is “_the setting-down piece_,” your case must be put by to dry thoroughly before use. The apparatus given at fig. 8 is very convenient for choking cases quickly, and is given in case you should think it worth while to make such a thing. Any boy with a fair notion of carpentering would find no difficulty in making it. It is simply a string passed over a small wheel and fastened to a pedal which works on a hinge close to the ground. A glance at the diagram will show you that by putting your foot upon the pedal _f_ the string may be drawn very tight. The case is choked at the point marked F. No choking can be done except while the cases are wet.

Now, supposing that you can do nothing else until your cases are dry, I will, meantime, introduce you to some of your tools. Fig. 9 represents the block and spindle over which your rockets are to be rammed. The case of the rocket is forced, mouth downwards, over this spindle by inserting into it the setting-down piece (fig. 4), which you have used before, and giving the handle of this some blows with the mallet (fig. 10). This operation has the effect of enlarging the choke to its proper size, and of making the mouth of the case very smooth and hard. The diagram (fig. 11), represents the steel spindle and nipple in its proper size. The part marked _g g_ is driven into the wooden block which forms its foot. Fig. 12 represents the rocket-case driven down upon the nipple when ready to be filled with its composition. Figs. 13, 14, 15, are three drifts of different lengths, pierced so as to admit the steel spindle, and to be used for driving the composition into the cases round the spindle. They are used in the following manner:—A ladleful of the composition is put into the case, and then driven down with the longest of these drifts by the mallet; then another ladleful driven with the same. Then a shorter drift is taken for the next few ladlefuls; then the shortest, till the case is full up to the top of the spindle. Then the unpierced drift (fig. 15) is used to ram in some composition solid, and to drive some clay upon the top of this. This operation will be described much more minutely in its proper place. Fig. 17 represents the “former” on which the cases are rolled.

These tools may be procured at a very reasonable price of Mr. Newman, 4, Augustus Street, Regent’s Park, London.

Having made you slightly acquainted with the various tools and apparatus to be used in making and filling rocket-cases, it will now be necessary for me to say a few words about their size and proportion, for much will depend upon accuracy in this particular. I have given you a sketch of four drifts to be used in loading your cases with composition. The longest of these I shall call _the first_; and the shortest, which is the solid one, _the fourth_; this being the order in which you will have to use them. The measurements that I am now about to give have reference only to _the straight part_ of the drifts, not taking their handles into consideration. The length of the first drift is 6 inches; second, 4½; third 3¼; fourth 2¾. The first three of these drifts are pierced or hollow, in order to admit the steel spindle over which the rocket is rammed. The first should be pierced to the length of 4 inches; second, 2½; third 1½.

Taking the exterior diameter of ¼ lb. rocket to be about 1 inch—and this measurement is near enough for our purpose—the former on which the cases are rolled should be ¾ of an inch in diameter, and the drifts about ¼ of an inch in diameter. The “former” should always be slightly larger in diameter than the drifts, because the paper that is rolled upon it is thoroughly wetted with the paste, and in drying will shrink a little; and, therefore, if your drifts be of the same size with your former, you will find considerable difficulty in getting them in and out of your cases; they ought to be a good easy fit. Twelve inches you will find a convenient length for your former.

In case you should wish to prepare rockets of other sizes, and in order that you may readily see the relative magnitude of cases of such sizes as are generally used in the art of pyrotechny, I here append a table:—Those which are called

1-oz. cases are about ½ inch bore. 2-oz. „ „ ⅝ „ ¼ lb. „ „ ¾ „ ½ lb. „ „ 1 „

In following the directions which I gave in my last paper for cutting up your imperial board and 70-lb. brown paper for rocket-cases, you will find that the case produced will not be a very stout one. Although I have made an excellent rocket in a case of such a thickness, you will, perhaps, find it advisable to use more paper and board, and prepare a thicker case. For this purpose cut your board in the manner that I have described before for your 70-lb. brown paper—that is, into _eight_ equal strips—and then cut each of your sheets of brown paper _lengthwise into four_ equal strips. By this plan you will be able to make very stout cases, which will not be at all liable to injury during ramming; and thus one sheet of board, with two of brown paper, will furnish eight ¼ lb. rocket-cases. You must bear in mind when choking them to contract the aperture till it is considerably smaller than you will eventually require it to be. The setting-down piece (fig. 4) has two uses: it is employed first in choking the case, and afterwards in driving or setting it down, when choked, over the steel spindle. The reason for driving the case thus down till the mouth is brought close to the nipple at the foot of the spindle is that the choke or aperture may thus be left of the proper size. This proper size is about two-fifths of the inner diameter of the case; and the aperture left immediately after choking should not be much more than one-fifth of the same inner diameter. The operation of “setting down” the cases is performed best, in my opinion, when they are perfectly dry and immediately before they are filled.

ROCKET COMPOSITION.

5. Now supposing your cases to be thoroughly dry and ready to be charged, the next thing that we must consider is the composition with which they are to be filled. Judging from the effect produced by rockets prepared by different makers, I should imagine that the formulas for their compositions are of almost endless variety. Some seem to prefer a very quick composition, which will raise the rocket to a great elevation in a very short time; others, one which will produce a large and rich tail of sparks not ascending so fast or so high. In my opinion, the mean between these two extremes is decidedly preferable: that which I aim at in rocket manufacture is to produce a very high, but not a very rapid, ascent; and when this my object has been properly gained, I have never had any fault to find with the tail of sparks which is thrown out. I may say, without any exaggeration, that I have experimented upon several hundreds of different compositions, varying first one ingredient and then another, increasing or decreasing them by very gradual steps, until I have come to the conclusion that the two following are the only ones worth retaining. But it must be remembered that it is not enough to have a good formula or two in order to be successful, for much will depend upon _the manner in which_, and _the care with which_, these are made up:—

No. 1. Nitre 16 parts. Sulphur 4 „ Charcoal 8 to 9 „

This, I believe, is a very old formula, and, provided the charcoal be properly prepared, may be found very useful and effective. I used this receipt for a long time, and thought it incapable of improvement, until, from a wish to try the effect of the addition of a little meal-powder, I came by chance upon the following, which I do not think can be surpassed:—

No. 2. Nitre 16 parts. Sulphur 3 „ Meal-powder 4 „ Charcoal 8 „