Does anyone know the chemical equation for KNO3/Al flash?
I am using a 50/50 ratio at the moment, and am just wondering whether it will be possible to optimize it using molar masses and such.
I am asking this becasue I am unsure whether the flash takes O2 from the surroundings, or just from the KNO3, and what it leaves as products.

I just did this on a napkin, but the chemical equation should be:

6KNO3 + 10Al --> 5Al2O3 + 3K2O + 3N2

So you can see that this reaction says you should have a theoretical 6/10 KNO3/Al ratio, so that's about a 60/30 ratio.

6mol KNO3 X 101g/1mol = 606g /10g = 60.6 parts KNO3

10mol Al X 27g/mol = 270g / 10g = 27 parts Al

Redox reactions like those that occur with flash powders NEVER take oxygen from the environment. That's too slow, so that's what an OXYDIZER like KNO3 is used for. The reaction gets oxygen from the oxydizer, and never from the environment.

and the extra 12.4% of your ratio ? :S

seems reasonable, thanks for that.

Some amount of oxygen will come from the atmosphere, how much varies. I have seen VERY fuel rich flashes that definatly had alot of the aluminum burning in the air afterwards.

And again K2O would immediatly start reacting with water forming KOH... which doesn't seem to really happen... and you do end up with some KNO2 and K2CO3... and if you have sulfur present you end up with some K2SO4 and SO2 too...

Generally with flash its more productive to just experiment and derive your formulas from actual tests to see what works best for your use. IE some flash comps might work wonderfully un-confined... but could be greatly optimized when confined. Some are geared for deep loud, some for sharp crack loud, some are geared for brightness, some for lots of power without much light, some are geared to act more like fountains or stars.

And of course the same compositions with different particle sizes will have different effects.

One of my good pyro buddies prefers to use relatively course magnalium and several oxidizers and additives to get the effects he wants... Then again he does big ones with strange compositions that one wouldn't normally think of as flash... and he has been experimenting for probably 10+ years.

So yeah, evaluate what effect your trying to get and try to gear your formula towards that.

and the extra 12.4% of your ratio ? :S

Mehh, I admit it's a genralized and idealized formula; it's the best i could do with a cell phone calculater and a napkin. It's just like bob said, there will be some unacconted for reactions. Also, i did give that in parts per reactant, not nessisarily in %... Like i said, it's genralized. Can you think of any more products that might be formed in the redox reaction?

Stoichiometry really doesn't paint half the picture of deflagrations.

There's a huge variance in temperature and local pressures, and a myriad of possible reactions that can take place under such extreme conditions.

LE composition ratios are determined experimentally to much greater effect than theoretical calculations.

I remembering hearing the actual ratios for KNO3/Al flash powder is 70 KNO3 to 30 Al.

For which use using which aluminum and how fine of nitrate at what altitude with what relative humidity?

Its preference, its always preference.

For which use using which aluminum and how fine of nitrate at what altitude with what relative humidity?

Its preference, its always preference.

Err? You tripping again? Because the first half of that has just been murdered.