823 replies to this topic

[schmoe_is_me]

Hello all. I am relatively new to pyro, but I am however a first-year chemistry major in college. I can make pretty good BP, but being as I am in college (a.k.a. away from where I can do pyro), I'm mostly working on theory of things I don't plan to do soon, if at all. I read a post on page 3 (I know it's an old post) saying that flash can be made with Potassium Permanganate and Aluminum in the ratio 70:30. Seeing this, I felt the need to check if that was stoichiometricly accurate. I came up with this equation:

2KMnO4 + 2Al > K2O + 2MnO2 + Al2O3

According to this equation, the proper ratio would be about 85.4:14.6. Then I realized that if you add up the valence electrons on each side (like I learned in Chem 101), there are 6 extra electrons on the left. Is my equation wrong? If not, wouldn't the stoichiometric ratio be best?

[minalth]

compositions containing potassium permanganate can be surprisingly friction sensitive, it really does not take much to set them off.

Needless to say this is undesirable

I think i am right in saying that they would also be more sensitive to static electricity and anything else that might set them off too.

its really not worth using the stuff, flash powders are (a lot) more than dangerous enough already without adding extra unnecessary risks

EDIT: there are other ways to achive the effect that would be made, lots of which are safer. still not a good idea for someone who is inexperienced, but safer.

standard bp is enough for most applications though, well made bp is not to be sniffed at.

Edited by minalth, 28 January 2007 - 05:00 PM.

[BigBang]

My chemistry isnt up to the required standard to be able to answer the question in theory, but i can answer your question in practise.

Many years ago, I used to make lots of different flash comps. using kMnO4, and in practice, you will get roughly the same results from most ratios from 60:40 through to 85:15 depending on the type of aluminium used.

Im not sure if you are asking this question in theory or if you intend to make it, but my advise is not to make flash using KMnO4, as in certain comps, it can be highly explosive...and will self-confine in amounts as low as 0.5g

KMnO4 is a very powerful, but unstable oxidiser, and is friction sensitive when mixed with various chems such as sulphur. Its use in pyro should be avoided, as there are safer chems that will do the same job.

[schmoe_is_me]

I meant in theory, but yeah I wouldn't use KMnO4 even if I did make flash- which I wouldn't as I have neither the experience or the need for it. But I'd still like to know why my equation isn't balanced properly; and if it is, what about the extra electrons?

[EnigmaticBiker]

I meant in theory, but yeah I wouldn't use KMnO4 even if I did make flash- which I wouldn't as I have neither the experience or the need for it. But I'd still like to know why my equation isn't balanced properly; and if it is, what about the extra electrons?

At a guess, the oxidation state of the Manganese has changed from VII to IV, since there are two moles of KMnO4 in this equation, it adds up to your 6 electrons.

Valency is usually a useful concept but where transition metals such as Iron, Manganese, Chromium etc are concerned it gets trickier. They all show a number of valencies depending on the compounds they are in.

Pretty colours though

[BrightStar]

I'd still like to know why my equation isn't balanced properly; and if it is, what about the extra electrons?

Without specific reference to permanganate, the simple explanation is that empirically, the best formula for the job is often not stoichiometric.

Magnesium based flashes, particularly coloured flashes, are often under-oxidised. The excess metal burns rapidly in the surrounding air and the slower burst gives a brighter light and more colour. Standard 70/30 Perc/Al flash is slightly over oxidised (66/33 is closer to balance), as this ensures complete combustion in its common applications - eg. confined for breaking crosettes.

In the opposite case, in some common lance, portfire and delay compositions, a greater excess of oxidiser is used to slow down the burning. The idea here is that the excess oxidiser will not be affected much by the environment, whereas an excess of fuel would burn and hence be unpredictable.

Edited by BrightStar, 06 February 2007 - 02:03 PM.

[pyrotrev]

I would also suspect (though I've not done any experiments to confirm this) that the over-oxidised 70/30 Al flash gives a better bang than the stoichiometric mixture on account of generating more gas: the stoiciometric mix should have all solid(well actually liquid at the temp) products. The low vaporization temperature of magnesium means that with excess fuel you'll likely generate a fair bit of gas and hence bang.

[Mehofjack]

From what i ahve heard Flash Powder is a very pwoerful mixture but my main question is........

Can it be bought from somwhere

ive been making some pretty sweet fireworks latly (small) and i heard that even for a small (water dynamite size) that this Flash Powder increases the power and shock by a high standard

[Asteroid]

No, is the short answer, due to its sensitivity, and the likelyhood of it being used illegally. Good BP will acheive the effect you're looking for, without hugely increasing the chance you'll blow your hands off.

[Mehofjack]

ok that helps me very much , thank you and also i got a new can of BP but i need to know if it it the best kind i can get

i got Pyrodex

it seems to work very well but i dont know if it is what i am looking for.

it is a muzzleloading propellant but i use if for my fireworks.

any tips.

thank you

[Mumbles]

Pyrodex isn't blackpowder in any way shape or form. It is a BP replacement.

[Frozentech]

ok that helps me very much , thank you and also i got a new can of BP but i need to know if it it the best kind i can get

i got Pyrodex

it seems to work very well but i dont know if it is what i am looking for.

it is a muzzleloading propellant but i use if for my fireworks.

any tips.

thank you

Pyrodex is not black powder ! Actually for most fireworks pyrodex works very poorly compared to BP. It's worthless as lift powder, for instance. Pyrodex is a 'synthetic' BP sub for BP in muzzleloaders, but it has a much steeper pressure exponent than BP. I.E. the burn rate is much more dependent on the pressure of the confinement.

If you must buy your BP, look for Goex, Wano, Elephant, or Swiss brand Black Powder, and get the coarsest you can find, as what you buy will be rifle or pistol powder, i.e. FFg ( the number of "F" = the grain size, the more F's the finer the powder. If you can find 2FA ( FA = fireworks powder ) all the better ) Fg, or cannon grade BP should be ok too. You can look up the grain size equivalents between FFg and 2FA online.

[cplmac]

No, is the short answer, due to its sensitivity, and the likelyhood of it being used illegally. Good BP will acheive the effect you're looking for, without hugely increasing the chance you'll blow your hands off.

I've heard this a few times, and I would like to chime in that BP in no way shape or form bears any similarities to flash powder. The only thing they have in common is that they deflagrate. I can't think of any way in which you can get BP to perform like flash powder. And Pyrodex like mumbles and Frozentech said is not BP. I tried pyrodex when I was first starting out as well, it just burns very poorly compared to BP for any real fireworks uses. I also heard that Elephant is going to become very scarce here pretty soon. Guess the factory was never rebuilt after it got trashed a few years ago and the supplies are starting to run out. Who knows.

[fishy1]

I've heard this a few times, and I would like to chime in that BP in no way shape or form bears any similarities to flash powder. The only thing they have in common is that they deflagrate. I can't think of any way in which you can get BP to perform like flash powder. And Pyrodex like mumbles and Frozentech said is not BP. I tried pyrodex when I was first starting out as well, it just burns very poorly compared to BP for any real fireworks uses. I also heard that Elephant is going to become very scarce here pretty soon. Guess the factory was never rebuilt after it got trashed a few years ago and the supplies are starting to run out. Who knows.

I disagree. Flash can and will detonate under the right conditions. BP can also, but only in very very large quanties. I agree with you though that flash and BP are not interchangable. Switch with BP.

[Frozentech]

I disagree. Flash can and will detonate under the right conditions. BP can also, but only in very very large quanties. I agree with you though that flash and BP are not interchangable. Switch with BP.

An old old topic for endless argument I guess it depends on your specific definition of detonate vs deflagrate. I have never seen studies proving that the burn front and shock wave in flash was greater than mach 1 though. It definitely behooves the hobby pyrotechs as a group to stick with deflagrate, because as soon as it becomes 'detonate' we are done with it, legally. Anyhow, you don't need detonation to make a loud explosion, just fast deflagration and some confinement. (self confinement =/= detonation ?)

P.S. I would love to see a long train of flash burn though ! ( like 100 feet or more long), with a goodly pile of the stuff laid out, maybe a few inches high in cross section. Would it confine, or just race at several 100 ft/sec ? Hrmmmm.....

Edited by Frozentech, 17 February 2007 - 10:34 PM.