The foregoing account concerning the art of pyrotechny, as it flourished in France during the eighteenth century, is of particular interest in connection with a study of present-day conditions by reason of the two contrasting phases shown. One of these has to do with the limitations of the art due especially to ignorance in the matter of many chemical facts now deemed vital to pyrotechnic purposes. The other fact has to do with the actual completeness of the art as thus practised. The narrative demonstrates that the French artificers wrought with a zeal and effectiveness so great that their achievement determined methods which have endured, essentially unchanged, throughout all the tests of experience until to-day.
The progress in the art shown during our own age is due wholly to the advance in chemical knowledge. It is true that the slowness of hand processes has to a considerable extent given way to the rapidity of mechanical operation. But the sole gain from this substitution has been in the matter of the quantity produced, rather than in the quality. The use of machinery for various purposes in connection with the making of fireworks was begun in the last quarter of the nineteenth century. Various mechanical devices are now employed for the commercial making of certain pyrotechnic pieces, but, too, even in the largest establishments, an astonishingly large proportion of the work is still done by hand.
It would be confusing, rather than enlightening, to enumerate separately each step in the advancement of the art during recent years. For the purposes of an historical survey, such as this, it seems advantageous to present, in contrast to the foregoing examination of the past, a summary of the more distinctive features in the situation to-day.
Thus, we may consider at the outset the list of chemical materials now commonly employed in the making of fireworks. It is not necessary here to attempt a precise description in each instance as to the nature of the substance or the facts concerning its discovery and application. Such information belongs to the chemistry of pyrotechny, rather than to its history. Moreover, simply the naming of the various modern constituents is impressive, when these are considered in connection with the materials at the disposal of the French investigators. The reader will remember the lament of the French authority on pyrotechny, who deplored the lack of adequate means for producing a green fire. His hope that some substance might be found to serve the purpose has been fulfilled. And as of this, so of other effects. The contemporary resources of chemistry free the artificer from any serious lack. He has but to avail himself of materials ready to his hand, in order, by the exercise of patience and ingenuity, to accomplish any ambition in the way of spectacular display.
The first use of fireworks in Europe, as has been pointed out, was by the Romans, who brought home with them from their foreign conquests a rudimentary knowledge of pyrotechny. It is, therefore, appropriate that in this concluding portion of our historical study we should revert to the Italians, who have, indeed, greatly developed the art within recent years - even to such an extent that their mastery of it may be regarded as sufficiently indicative of contemporary attainment.
In 1916, the handbook of Di Maio, an Italian authority, included the following materials in its list of requisites for the manufacture of fireworks:
Used for white fires. Crude antimony (sulphide of antimony) is employed in the production of a bluish-white flame.
This is made plastic with water, and molded in any desired shape, to serve for plugging cases, etc.
Used to secure a yellow color in fire.
The effect is to increase the vividness of colors.
Used to moisten various compositions and increase the brilliancy of the fire.
Used with nitrate of strontium in producing violet-colored flames.
This gives to the flames tints varying from red to violet.
There are two sorts - the light, made from soft wood, and the heavy, from hard woods. The first is easily inflammable, and is used in the making of ordinary fires and jets. The second is of slow combustion, and is used in the composition of various pastes for jets, colored flames, stars, etc.
This should be both smooth and pliable, yet strong, not easily breaking or cracking. The paper used for wrappers is of various colors, to indicate the particular contents of fireworks. For port-fires, ordinary writing paper, or press paper, of a lighter and weaker texture may be used.
This is prepared by pasting together two or three thicknesses of cardboard with wheat paste. For incombustible cases, the pasteboard is made up of sheets fastened together with a fireproof paste. For cases of large caliber to spurt fire, strawboard is used.
Employed in the production of green flames.
Used for the sake of its explosive violence, in connection with other substances.
This may be either of rye or of wheat flour. The flour is moistened with eight and one-half times its own weight of water, and boiled slowly about one-quarter of an hour, while being stirred, until it begins to thread. To prevent souring of the paste, a little alum should be added to the water before boiling the paste.
It will be noted here that no reference is made to the virtue of the alum as tending to prevent the inflammability of the paste. The statement of Di Maio concerning the reason for the use of the alum is corroborated by all modern makers of fireworks, who regard the alum simply as a preventive of acid action in the paste. Yet, it will be remembered that the first use of this substance was by French investigators, who employed it as a substitute for common salt, which the Chineses added in order to render the paste incombustible. The French artificers found alum preferable to salt, since it resisted humidity, and served equally well in its resistance against fire. They nowhere show any appreciation of the fact that the alum served also as a preventive of chemical change in the paste.
This forms a part in various compositions, according to formulas hereinafter given.
This should be white, and should leave only a small residuum of ash after burning. It is employed in the preparation of fuses or matches.
Dissolved in an equal part of water, this forms a dense solution, which has strong adhesive power and a neutral reaction. It is used in small quantities, when moistened with water, to give consistency to the composition of stars and grenades. It has the quality of not delaying the combustion of any material into which it enters.
Used in powder form to give consistence to various compositions. It has also the effect of making combustion slower.
This is valuable both for its adhesive qualities and for its impenetrability to moisture.
These are of various metals. They should be fresh, unchanged by oxidation. To secure particularly effective scintillations, bits of iron or copper wire are sometimes used to secure green effects in the fire from fountains, and zinc filings are used to secure a white light which tends toward a bluish tint. The filings are passed through screens, and thus are divided into three sizes, to be used according to the various calibers of cases.
This is secured by combustion of resinous materials. The black powder may be rendered hydrophilous by boiling it for some time in a slightly alkaline solution, while stirring it.
This is used in compositions for green fire, as is the chlorate of barium.
This is used where red flame effects are desired.
Essential in the making of powder.
This serves in producing blue flames, but the color is less vivid than from copper ammonium sulphate.
This, mixed with pitch, is useful for softening certain pastes, so that they may be the more readily manipulated.
This is familiarly known as blue vitriol, and is employed for producing various color effects. The copper ammonium sulphate is most important in securing a fine shade of blue. It has the advantage of not causing spontaneous combustion when mixed with chlorate of potassium.
The color effects are similar to those from the nitrate of strontium.
The uses of this are various according to the composition into which it enters.
These are of various weights and strands, according to the particular purpose for which they are designed.
These may be of caoutchouc, copal, shellac, or collodium. They are employed in coating fireworks, to prevent the penetration of humidity.
The foregoing list of chemicals by no means embraces all the many new compounds which are making themselves important factors in the manufacture of pyrotechnic articles. Other chemicals and materials used in this country will be noted later in the text.
In comparing the formulas recommended by various artificers in pyrotechny, the casual reader will often wonder at the apparent diversity in different formulas used for the same purpose. It must be borne in mind that only a physical comparison will establish the relative efficiencies of various formulas recommended by the artificers engaged in this work. The Italians, French, and English, as well as Japanese, use formulas in many cases quite different from those preferred in this country for producing the same effects. Consequently, the tabulation of these various formulas, as used in the different countries, is given largely for the purpose of comparison and to aid the experimenter engaged in research toward developing an improvement in the art.