A Heretic's Guide to Roman Candles
Originally published in Best of AFN IV:
There is the so-called "right way" to make Roman candles. Classic pyro writers such as Weingart, Lancaster and Brock tell you how to do it the right way. Other pyro writers follow suit. But "right way" Roman candles are in fact just boring!
Sure there have been many innovations such as exploding stars, color changing stars, and humming stars or "bees". But these have reached (in my mind) the bo-o-ring stage. The classic device which shoots a series of stars which fly to the same height and then extinguish is just one big yawn. Ah - but there are ways to make Roman candles more exciting!
My first thoughts at challenging the orthodox doctrines making came with my early experiments in this area. Watching how low cost Class C performed only strengthened my convictions. These did not perform according to the books which described how "good" Roman candles should be made but they sure did some unexpected fun things.
The "proper" way to make Roman candles is to ensure that the propellant is adjusted in such a way as to project each star to exactly the same height. Ideally each star should extinguish just as it reaches maximum height. We are told by the Roman candle high priesthood that to achieve these goals is a measure of one's skills in the pyrotechnics arts. Failure to achieve such automatically assigns one to the ranks of lesser mortals.
In addition to the above goals, a "good" maker of Roman candles must pay careful attention to the ramming of the "candle comp" or fuse. A mortal sin is to ram in such a way as to cause too short a burning time. There is (supposedly) something just proper and decent about having a respectable pause between each star being shot. And no one has even dared to consider firing more than one star at a time from a single tube.
Well there are more fun ways to make Roman candles and the sky's the limit when you start to consider all the many variations and possibilities.
I must confess that in the early days of my pyrotechnic endeavors I was steeped in orthodox Roman candle beliefs. I got rather annoyed every time I witnessed a Roman candle shooting its stars to different heights. The cheaper Class C candles almost inevitably dropped the first star on the ground. The second star would often extinguish just before ground level. The other stars would improve on this until finally the last star would perform more or less correctly. I really felt cheated by these "below spec" candles.
My own attempts at making Roman candles ended up being better than the cheaper Class C items and this gave me a certain amount of satisfaction. It took me quite some time to more-or-less perfect them and I started asking a lot of questions along the way.
My first question concerned the right type of propellant to use. I had no source of Black Powder in those early days and had to try and find an alternative. I opted for some (shock! horror!) flash powder. With some drawbacks, this worked pretty well. Number one drawback was trying find the right amount of flash. Even a tiny amount would often send the star into orbit and would often cause it to blow out blind. The second drawback was that the flash lived up to its name by producing a blinding flash of light. This would frazzle the eyeballs and thus diminish one's enjoyment of watching the star fly through the air.
A third drawback was flash was good for only two stars per candle. This was partly because, for safety reasons, I opted to press the components gently into each tube, rather than ramming them. I used a less violent flash than that normally used for flash crackers; it was made with potassium permanganate and atomized aluminum powder.
I wasn't too happy with my flash candles and looked around for an alternative. Someone I worked with offered to trade some nitrocellulose used for charging cartridges for some firecrackers. She wanted the firecrackers to scare some pesky bark-in-the-middle-of-the-night-at-nothing dogs belonging to her neighbor. The firecrackers worked better than expected. After a while, she just had to appear at her window to stop the dogs barking. Unfortunately, the nitrocellulose powder didn't perform as well.
Yes, there are many dire warnings about the dangers of using nitrocellulose. Even a tiny amount of this stuff is enough to propel a heavy bullet many hundreds of feet, so imagine what it would do to something projected from a Roman candle! And there is always the danger of the tube bursting! The dangers were highly exaggerated.
Yes, nitrocellulose confined in a tight space will explode violently. Thus only a small amount is needed in a sealed cartridge case to send that bullet flying. In Roman candles, however, the situation is different. Even a large amount packed tightly produces a minimal amount of propulsion. So nitrocellulose in my Roman candles was just one big flop. The remainder of my nitrocellulose was used as a binder for stars.
Eventually I managed to make some Black Powder which did a good job of projecting Roman candle stars. But the question still remains in my mind: are there any other propellants out there which could do the same job cheaper or better?
The next major question is: should all the stars be projected to the same height? My answer: no, not necessarily!
Projecting the stars to different heights creates a certain delightful diversity for the audience. Having each star travel higher than its predecessor creates the feeling of something getting better and better. Is it a sin to let the star fall before it has extinguished? Well, this happens with other fireworks so why not with Roman candles. It can be quite fun to watch flaming stars hit the ground, being sure of course that no other ignitable materials are around. You can naturally opt for stars which extinguish just before hitting the ground.
Here's another thought. Why not add to the diversity by having stars of different sizes?
Brock describes some pyros who did just that but finally abandoned the idea. The thought behind this idea was to make stars of different sizes and keep the Black Powder projecting charges the same size. This, in theory, would result in all the stars being projected to the same height. Manufacturing practicalities aside, a perceived disadvantage with this scheme is each flaming star differs in size from the others.
To a heretic a perceived disadvantage can actually be an advantage, and a good one. Stars of different sizes create different flame sizes and have different burning times - two interesting diversities. One can naturally combine these two diversities with each star being projected to a different height. So you see where just a little bit of heretical lateral thinking can lead us!
While popular folklore accepts the concept of having different size propelling charges, it hasn't gone as far as entertaining different burn times. Why not progressively shorten the fuse after each star? Here the candle will start off at a leisurely pace and quicken as time goes by. Figures 1 and 2 illustrate these two conceptual differences.
For clarity, these drawings show only the stars and omit the fuse and propellant. A variation on this theme is to add a dramatic climax such as having the last star behave differently. For example, this could be an exploding star where the others are not. Another surprise variation is to make the fuse time for the last star longer. Here the audience thinks that the Roman candle is finished when suddenly a surprise last star is shot!
It's great fun having the stars being shot in quick succession. This "machine-gun" effect first came to my attention with a Chinese Class C candle - all stars were out of the tube before the first star extinguished! Unusual, but great. This has given me a few good ideas.
Idea number one was to replicate the performance of the device which gave me the machine-gun candle idea. Here the stars are packed tightly together and the aim is to fire them all in one quick burst. The effect is a ra-ta-ta-ta-ta-ta-ta-tat, just like in the gangster movies. (see Fig. 3) Idea No.2 calls for a slower firing rate, a pom-pom-pom-pom like an anti-aircraft gun. (see Fig. 3)
Idea number three has a more purist infantry outlook. Here it is not proper to fire long bursts from an automatic weapon but rather short three-round bursts. A Roman candle can be modified to do just that by firing stars in groups of three, as shown in Figure 4.
Of course, one can experiment with the three concepts I have outlined above by combining two or all three of them in a single candle.
Doctrinal purity in Roman candles demands that only one star is fired at a time. Even our deviant machine-gun candles conform to this dogma. Well if we can have candles which behave like machine-guns, we can surely have shotgun type candles. The fireworks world already has these in the "sawed-off single shot" variety we refer to them as mines. Now imagine a mine which has a longer tube and can fire more than once. Voila! A mine which evolves into a special type of Roman candle a shotgun candle! Fig. 5 shows one shot of such a candle.
A final word about a heretic's approach to Roman candle stars, and good news for many pyros. Yes, you can use cut stars in Roman candles! You don't have to restrict yourself to pumped or laboriously made round stars. Cut stars will work with a bit of extra propellant. This extra propellant is needed to make up for the loss of efficiency due to the cut stars not sealing properly in the tube. But if you can afford the extra propellant, cut stars might be your way to go.
So much for stars. On now to tackling the next sacred cow, the revered "candle comp".
Candle comp is treated by most manufacturers of Roman candles as just another type of fuse. In many Roman candles that's all it is, fuse. As such, with few exceptions, the burning of candle comp is boring. A few makers of Roman candles have, however, by accident or design, created candle comp which actually burns in an attractive manner. I have noted some candles which have been pretty little fountains as well as projectors of stars. This is really the way to go - and it shouldn't be too difficult to achieve.
A lot of attractive fountain effects can be achieved with variations in just the three main candle comp ingredients: potassium nitrate, sulfur and charcoal. Here the most important ingredient is the charcoal. Different types of charcoal can give different effects. One can cautiously venture further by adding other ingredients to the candle comp. I say cautiously because many fountain compositions are not suitable for ramming. And the ramming process in Roman candles has its dangers under even ordinary circumstances. But does one always need to ram Roman candles? Here is even more food for deviant heretical thought.