|Photo by StarrGazr, used under Creative Commons|
We live in an age where the eye is constantly bombarded by visual stimuli. The survival of a television producer, as well as some very important economic results to a number of people, depends on his being able to dazzle the eye of the viewer to a greater extent than his competitors for the viewer's time.
Thus, it should come as a surprise, perhaps, that in our house on a certain night in January, and I suspect our house was not alone in this respect, the family was not to be found at its usual place before the TV set. Instead, they were crowded around the southeast windows watching, at a distance of about three miles, that part of a display of pyrotechnics which was not obscured by South Mountain. To this enduring fascination which fireworks seem to hold for the human imagination, I would like to turn our attention tonight.
Fireworks are usually considered to be any combination of chemicals capable of combustion without necessarily obtaining oxygen from the atmosphere, and intended primarily for either noise or visual effects arising from that combustion. The first fireworks, then, by this definition, were probably those used in China in the eleventh century, A.D. Note that this definition rules out the earlier use of what was called "Greek Fire" in Byzantium around A.D. 676, where the visual and audible effects were secondary to the primary goal of setting fire to the enemy.
It is interesting, however, to compare the formula for Greek Fire with that for the Chinese fireworks of four centuries later. Greek Fire consisted of rosin, sulfur, bitumen, and (almost certainly) saltpeter, although the early formulas do not mention it. This mixture was rammed into a copper tube and ignited, the resulting spurt of fire directed for military purposes. Although the two may have arisen independently, it is not unreasonable to hypothesize a historical connection with the Chinese fireworks reported by Marco Polo to have been used for amusement, not military purposes, and which consisted of powdered charcoal, sulfur and saltpeter, rammed into a tube of bamboo. Making allowances for the different materials native to the two regions, the formulas are about as close as they could be.
Saltpeter is a key ingredient in both formulas, since firework devices will not work properly unless they have some means of obtaining oxygen other than from the air. It seems curious that the ancient formulas for Greek Fire do not mention it, but speculation suggests two possible reasons for this. First, it may have been that the true formula was a well kept military secret, and the one essential ingredient was deliberately left out by the recorder. It also seems possible that the ingredient bitumen, which even today is not a well defined mineral chemically, consisted in some part of potassium nitrate, the principal constituent of saltpeter, and about the only good oxidizing agent for fireworks purposes that occurs naturally in any reasonable proportions.
When the technology of pyrotechnics reached Europe from China, it was the military potential, of course, that appealed immediately to Europeans. Fireworks for amusement purposes do not seem to have had much existence independent of the military, although it was not uncommon to celebrate a victory with a fireworks display. At first, these displays almost certainly consisted of a firing off of some surplus shells unexpended in the battle, but they later came to be quite elaborate, and specially designed for visual effect. Special military pyrotechnicians were retained for the purposes of designing victory displays, although I'm sure there was no objection if these pyrotechnicians discovered, in the course of designing a victory display, an effect that was also militarily useful. It might seem at first that retaining a technician to help in celebrating a victory before the battle has been fought is somewhat bold, but if so, this is a boldness not unknown to politicians in our own time.
The art of fireworks construction as carried on in our own times (and there has been very little change since the late 19th century) consists of finding ways to combine and control the timing and direction of a relatively limited number of basic fireworks effects. The first, and perhaps most important of these effects is the force that arises from expanding gases when ignition takes place in a confined space, and for this purpose, the centuries have permitted very little improvement on the classic combination of charcoal, sulfur and saltpeter, which is still effective enough that it is commonly used today, since the ingredients are relatively inexpensive and easy to obtain. There is some advantage in substituting a metal such as powdered aluminum or magnesium for the material being burned, and potassium chlorate for the oxidizing agent, but these ingredients are hard to handle in some ways, and the relatively slight improvement over the classic formula is often considered not to justify the extra expense.
The second important fireworks effect is sparks, which may be obtained from the classic mixture, but here substantial improvement may be gained by adding a powdered metal. Iron will generate large bright yellow sparks, and the intensely bright light generated by the burning of powdered magnesium or aluminum needs no description to most of those here.
The final important effect for visual fireworks displays is the colored fire effect. Here the classical mixture leaves much to be desired. The combination of charcoal, sulfur and saltpeter burns with a dull yellow light, not unlike a wood fire, and except as noted for sparks, it is not often used as the colored portion of a fireworks device. A huge variety of colored fire recipes exists, usually relying on a metallic salt to impart color to the basic mixture, Thus, substituting strontium nitrate for the potassium nitrate leads to red fire, addition of boric acid leads to green fire, etc. Usually, these colored fire combinations do not burn quite as well as the basic mixture, and they are always more expensive, and therefore used only when necessary and where they will be seen.
About six basic fireworks types result from a combination of these basic effects:
- Stars are basically just bits of colored fire. In the elaborate commercial displays stars may be used as the terminal effect of some other type such as a rocket or shell, or they may be arranged to spell words or show some symbol of the celebration such as a flag.
- Shells involve a charge placed in a hollow tube with the force resulting from ignition used to propel some sort of payload into the sky. An important distinguishing characteristic of the shell is that the charge itself is not propelled, but remains in the tube.
- Roman candles are similar to shells, in that a retained charge propels a payload, but distinguished by the fact that the payload in this case is an already ignited star. (The payload in a shell is controlled by a fuse that does not ignite it until sometime after it is aloft.)
- Rockets depend on the expanding gases in a charge to propel the charge; and sometimes a payload as well, into the sky.
- Fountains are basically rockets pointed toward the ground, so that the shower of sparks is propelled into the air. Usually the sparking power is improved by the addition of some powdered metal.
- Pinwheels are rockets mounted on a revolving wheel so that the propelling force and shower of sparks are resolved in a circular direction. As with fountains, powdered metal sparks are a usual addition to enhance the visual effect.
Be that as it may, fireworks have, for some time, been subject to considerable legal restriction. A 1731 colonial Rhode Island law forbade the “unnecessary firing of guns, pistols, squibs and other fireworks." Pennsylvania adopted a similar law in 1751, and the Massachusetts law on the subject dates from at least 1836, although it has been strengthened at least once since then.
All told, 42 states and the District of Columbia now have laws restricting or prohibiting the use of possession of fireworks within their borders.About fifteen of these, including California and the District of Columbia, permit the use of fountains and stars, but prohibit the other types. The Massachusetts law on the subject is a classic example of legal overkill, and bears quoting for that reason: “No person shall sell, or keep, or offer for sale, or use, explode, or cause to explode, any combustible or explosive composition or substance, or any combination of such compositions or substances, or any other article, which was prepared for the purpose of producing a visible or audible effect by combustion, explosion, deflagration or detonation..." If I interpret that literally, it means that if I light a match, and decide to watch the flame instead of lighting my cigar, not only am I in trouble, but so is the tobacco store that gave me the matches.
I want to conclude this with a consideration of some of the psychological factors that make fireworks appeal to us, but before I do, and perhaps by way of illustration, I want to recount some of my personal experiences with fireworks. When I was fifteen, my parents indulgently permitted me to mantain a chemistry lab in a spare room in the basement of our house. The lab started out with honest and honorable intentions, and I did learn a lot of chemistry as a result. Chemlcal experiments fall into two categories, however, those that are interesting enough to repeat, and those that are not. Even today I have no desire to again observe the fact that litmus paper turns blue in the presence of a base, and due consideration for the limited attention span of a 15 year-old boy makes it easy to see why I soon became sated with experiments of that type.
For that reason,those expermments which were repeated tended to be those with the more spectacular effects, and I began concentrating more and more on fireworks. At first, these were confined to the very limited formulas which could be set off in the lab, but gradually I began to increase the quantity of the ingredients to the point where it was necessary to make use of the main part of the basement to fully enjoy the effects. Finally, even that became inadequate. A surprisingly small quantity of fireworks materiel can make enough smoke to completely fill a fairly good-sized house, and my parents absol-
utely forbade the further detonation of fireworks indoors.
For that reason, I arrived at the penultimate event of my career as a juvenile fireworks manufacturer under some severe restrictions. It was a mi-April day in 1954, almost exactly 20 years ago, and the weather in the Hudson valley at that time of year tends to confine itself more or less to cold and unremitting rain — exactly the kind of weather absolutely prohibitive to an outdoor fireworks display. I had as my guest a contemporary fellow experimenter, and the two of us having recently perfected our manufacture of rockets, were attempting to adapt that knowledge to the manufacture of a roman candle. We developed several trial models, and began to give consideration to the search for a suitable testing ground. Clearly, both the house and the great outdoors were out of the question, but at the back of our yard was a large outbuilding, intended as a garage, but now used mainly for storage purposes. This, we concluded, if not the ideal spot, was at least adaptable for use as a test site.
We adapted it by opening the two swinging doors to their widest, and placing the roman candle on a table with the business end pointing out the open end of the garage.
It is unwise to be satisfied with a partial scientific education. Learned as we may have been in chemistry, we were ignorant, or at least forgetful, of the practical effects of Newton's first law of motion. The proto-roman candle turned into a rocket, and instead of firing balls out the door, it fired itself into a mattress at the closed end of the garage. Dousing the matress with water did not succeed in extinguishing the sparks, and that night the garage burned to the ground in a conflagration still quite well remembered in that neighborhood.
That was not quite the end, although it should have been. Ordered by my parents to rid myself of all chemicals and supplies in any way related to fireworks, I began searching for a buyer. To facilitate this, I included in the purchase price an offer to mix the ingredients purchased to the buyer's specifications, and on this basis, I was able to sell the entire quantity quite quickly. The buyer's specifications, in this case, happened to be that we would make a giant roman candle out of a well pipe that had been sunk in his yard, but had reached rock before it ever reached water. Our intent was to use up all the chemicals in such a way as to create a varied and memorable display. It was at least the latter, if not the former.
For reasons that are still not entirely clear to me the gigantic experiment did not go at all as we planned. After filling the pipe with the ingredients, we poured down a combination of chemicals that will ignite spontaneously in about 6o seconds, and drew back some distance to witness the display. It is fortunate that we did; in about 60 seconds there was a single tremendous roar, and the pipe spurted into the sky, spraying mud on all buildings in the vicinity, and leaving a crater about five feet wide and equally deep.
I never attempted such an ambitious experiment again. I hope that these anecdotes are useful in illustrating why fireworks have endured as human amusement in spite of danger and legal restriction, and even lately in spite of better endowed and more commercially profitable entertainment. I note several psychological elements that seem to me to explain the appeal.
First, and perhaps most basic, is the natural attraction that light has for humans, and all living things. For most of mankind's history combustion was the only source of light known to him, other than the astronomical bodies, most of which he showed his admiration for by literally worshipping. If this was the basic, and original element, it came to be joined by another, that of danger, and, more recently, outright prohibition. The same argument which holds that open availability of narcotic drugs would lessen their appeal can be applied to fireworks, although I would agree in both cases that human judgement cannot always be trusted to be the controlling factor in the avoidance of excesses. In fact, in my own case at least, I consider myself fortunate not to have been exposed to the temptation of open availability of fireworks any more than I have.