Formula 1 Fireworks

[Barton Ostby]

Bluethat's the case with some sabots -- most commonly for some kinetic (non-explosive) AP rounds. But, a sabot is not required to surround the projectile in order to qualify as one; they often trail the round. In fireworks, for some hundreds of years, the traditional term used for your 'piston' in fireworks has been "sabot".

Some use the term 'wad', but that is also not correct, unless the thing used IS a wad... that is, slightly larger than the gun i.d., and compressed to fit into the tube. A sabot is smaller than the i.d. and is often used to cushion a delicate shell against lift force, or to help uniformly lift all stars in a mine to the same height. Those in mines are often perforated to allow lift gasses to mix in with the stars.

Thanks piroart for the D1 comp. I did notice after I asked that you mentioned it already. It's one of the many star comps Ive yet to make. I have made winokur 20 with large flake alum. Not as good as alcoa 120. Needs to get some from hobby chemical supply. Have you tried wino 19? That one uses granular magnal 100-200 mesh and it really flashes big and bright but not as dense.

That'll work excellently and it matches the blue I have made with CuCl2 - But the burning properties are better than mine since I rarely ever used hexamine (I used dextrin, PVC and shellac)! It seems like the hexamine is a bit high but perhaps the paper you lit it on is producing the orange tip in that video.

Good luck with your future devices.

thanks, I don't have Copper(II) Oxychloride and Gum Arabic, but I can change it to Red Gum.. Do you know what Copper(II) Oxychloride doing in this formula ?

I have tryed to find some compositions here, but I can't..

So while I await my application for an Aquire & Keep to be processed (the Greater London ELO said he received over 100 applications after Christmas so it could be a while) I figured I needed something exciting to keep me busy which won't disturb the neighbours too much. Hence I felt some colour experimentation coming on!

Now the supply of perchlorate has basically dried up and I've got to make my left over stock last (so only using it for nice stars for special occasions), I was wondering if it was possible to make coloured stars using old fashioned potassium nitrate, of which I have plenty.

Now to create a hot enough flame using potassium nitrate as the oxidiser is clearly going to require a metallic fuel to get the flame temperature up to a high enough temperature to achieve a colourant in the gaseous phase. The choice of metallic fuel is going to be aluminium, magnesium or magnalium. Some basic chemistry research reveals that the metal with the highest heat of combustion (the heat given off when it is combined with oxygen from its elemental form) is aluminium, so that answers that question. So we have so far:

So for my first test I'm going to simply try to see if I can get the composition to get hot enough to produce the basic colour from an added metal salt (without a chlorine donor). These colours vary slightly from what we usually take to be the classical colours produced by various metals. Thanks to Shimizu's book here are the colours I'm looking for:

Now to the ingredients. I have most things available to me but to make it easy for people to use the formulae, I'd like to keep it down to easily accessible chemicals. Clearly an aluminium flame is necessary so I'm thinking to base the formulae on a basic nitrate flash (relatively insensitive and burns nice and hot). To make the formulae even more insensitive and because it's easily bought from art stores, the aluminium I'm using is the atomised variety. Obviously nitrates and aluminium have the potential to react so I'm adding 2% boric acid (which annoyingly affects the flame temperature but is necessary). The metal colourants I'm going to use are all carbonates as these can be bought from pottery supply stores and they're easy to work with and relatively non-toxic.

I'm simply going to test unconfined piles of composition (I know, making them into stars changes the burning characteristics but baby steps first!) first using the following general formula, by weight, with everything except the aluminium mixed by passing through an 80 mesh screen, then the aluminium diapered in:

The calcium carbonate composition burnt a bright orange colour, the copper carbonate composition burnt a bright white with tinges of very pale green at the edges, the strontium carbonate composition burnt a white with tinges of orange at the edges and lastly the barium carbonate composition burnt a bright white colour. Nitrate based flash on its own of course burns a nice white so can't really say much about the barium, but the others seem to have worked somewhat! Now to work out compositions which include some chlorine donors...

As with any good science, the key to good results is lots of repetition! So if anyone out there would like to give these a crack, then please do, and report back what colour you get (and feel free to change the formula if you need to, i.e. use flake aluminium or copper oxide instead of carbonate etc). Happy experimenting!

Colours largely came into fireworks with the development/discovery of chlorates, then perchlorates. However there are just a few comps listed in which use nitrate for colours, some as you say needing magnesium -a hot burning metal- to be hot enough to make colour.

Now for the chlorine donor tests! I've made up some formulae utilising a base of nitrate flash plus some extra oxidiser and parlon as a chlorine donor to give the following formulae for basic colours (plus I swapped to using copper oxide for the blue because the chemistry is a bit simpler):

I'm going to try and substitute in some magnalium for the aluminium and see if that takes away some of the white from the flame (magnesium doesn't add a white colour to flames), although I suspect the barium star won't be hot enough to produce a green colour regardless of ingredients.

Hats off to anyone who is prepared to tackle a project like this, which may prove to be both long and challenging. Given the current UK need for an explosives precursors licence in order to purchase (and, within a year, to possess) potassium perchlorate, coupled with increasing concerns in the USA and elsewhere regarding the environmental impact of perchlorates, it seems to be well timed.

From general considerations of the physics and chemistry of pyrotechnic mixtures, reasonable reds and greens should be possible. Blue may prove more difficult, if only because there are so few suitable copper-containing compounds.

So an update on how this is going. I have some formulae which when I finally get them ignited, burn with a very small but coloured flame - interestingly the blue being the easiest to get to give some colour. They still need a little tweaking so once I'm happy I'll post them for everyone to have.

My current problem is that the ignition temperature has to be very high (Black Powder prime isn't quite cutting it and a loose pile of composition doesn't seem to ignite full stop). The formulae currently contain Potassium Nitrate, Sulphur, PVC, Aluminium and metal carbonates. I think the best call would be to incorporate some Red Gum but without an empirical formula for it, I've no idea where to start working out the ratio between Nitrate and Red Gum I'm going to need to have it burn adequately. I know Red Gum is a very complex mix of compounds so an empirical formula would be a massive over simplification, but it's at least a starting point, if anyone knows a close enough formula?

Anyone have any other ideas how I can reduce the ignition temperature without adding too much extra fuel to the stars? I'm starting to get the feeling maybe I'll just have to settle for having to prime stars with a silicon prime to get them to ignite.

It was mixed by passing through an 80 mesh screen. The composition burned an orangey-red colour with a pretty good flame, however it did burn very sluggishly and sort of stopped and started (a bit like a strobe mix?). I get the feeling this is mainly due to the PVC, which isn't melting during the reaction and so heat isn't propagating through the composition. I'm going to try and mill the PVC powder I have with some Charcoal or some Red Gum and see how this affects its ignitability in a Potassium Nitrate mix. I'm also aware there's a high carbonate content which is going to be a flame retardant so I'm going to try a formula with less Strontium Carbonate and more oxidiser and see how that affects it.

An update on the Aluminium experiments. I tested a bunch of formulae containing different proportions of Aluminium to ascertain what gave the best burning characteristics and lowest ignition temperature. So far my best formula has been:

It was mixed by passing through an 80 mesh screen and diapering in the Aluminium. Of all the formulae I tried this gave the best flame envelope burning quite bright but still retained an orangey-red tinge to the flame. I suspect the carbonate is only decomposing to Strontium Oxide in the flame and no Strontium Monochloride is forming, hence no deep red is seen. I'm going to see what happens if I make adjustments to this formula to try and increase the temperature by lowering the Charcoal and Sulphur content and keep you all posted. I'm also working on some Copper Oxide containing formulae so I'll let you know how that goes.

I've been working on the Copper Oxide blues formula and I've been having a lot of trouble with it. The formula is based on Copper Oxide thermite to attempt to get enough heat into the mix to produce some colour. However, regardless of what organic fuel compositions I mix it with, I can't get it to reliably ignite and burn through. In fact in half the tests I've done, the Aluminium doesn't seem to have ignited at all. I'm going to see if I can work out a formula based on Nitrate Flash which might burn hot enough to decompose Copper Oxide and allow it to react with Aluminium, thus producing some Copper in the flame which I can try and get to react with some chlorine. If anyone has any suggestions, that would be lovely!

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