823 replies to this topic

[damocov]

I seem to remember that the main danger of AN is that it can "cake" or clump and it's when these cakes are broken up that the fracturing of the crystals can cause an ignition, not technically a spontaneous decomposition.

I think wikipedia has a number of AN related accidents listed, the two classics from memory are a boat in texas and the BASF factory in germany.

[Plays with Fire]

Okay, first please don't take this question the wrong way; i am in no way suggesting that i dont believe you, that you're wrong, or that i wont take your advice. I will definately *not* attemp any of this, im just hoping one you can tell me why my logic (or lack thereof ) is flawed as so I can learn for the future...

I read in Wikipedia that AN has a 20% oxidation balance (i know now that means for xplsvs, but bear with me) so it produces 20% of its weight in free oxygen. I also read that a a thermite reaction (iron-oxide + aluminum = molten iron + aluminum-oxide) is highly exothermic, and I assume thats because of the aluminum combining with the oxygen. So, me in my slightly schizophrenic head , firgured that if they were mixed in the proper proportions that the AN would give it's excess oxygen to the Al creating a combustion much like flash.

Please tell me where my logic is flawed as so I can become ever-so-slightly more of a learned person.

With shame,
Plays with Fire


P.S. I've read a little more and I see what your saying about the hygroscopicity (possibly a word) of AN and its affect on the Al, and the dangers/reputation on any AN mixure, but, *purely* curious (i like my limbs ), what would happen...if anything, or would it just be diasterous?

[fishy1]

Okay, first please don't take this question the wrong way; i am in no way suggesting that i dont believe you, that you're wrong, or that i wont take your advice. I will definately *not* attemp any of this, im just hoping one you can tell me why my logic (or lack thereof ) is flawed as so I can learn for the future...

I read in Wikipedia that AN has a 20% oxidation balance (i know now that means for xplsvs, but bear with me) so it produces 20% of its weight in free oxygen. I also read that a a thermite reaction (iron-oxide + aluminum = molten iron + aluminum-oxide) is highly exothermic, and I assume thats because of the aluminum combining with the oxygen. So, me in my slightly schizophrenic head , firgured that if they were mixed in the proper proportions that the AN would give it's excess oxygen to the Al creating a combustion much like flash.

Please tell me where my logic is flawed as so I can become ever-so-slightly more of a learned person.

With shame,
Plays with Fire
P.S. I've read a little more and I see what your saying about the hygroscopicity (possibly a word) of AN and its affect on the Al, and the dangers/reputation on any AN mixure, but, *purely* curious (i like my limbs ), what would happen...if anything, or would it just be diasterous?

well, it's hydroscopic, like you said, it would probably get wet and unusable within a day or two, so you couldn't keep it for long, and i'm sure thier's incapibilitiles.

[karlfoxman]

Not just wet and unusable, aluminium will react with moisture too so it is a dangerous mixture when the two are added. Just stay away from it end of story. Stick to the good old blackpowder, this in itself is an art to make and well worth alot of time. Good luck with your pyrotechnics and play safe, common sense and a good head is needed.

[Frozentech]

Not just wet and unusable, aluminium will react with moisture too so it is a dangerous mixture when the two are added. Just stay away from it end of story. Stick to the good old blackpowder, this in itself is an art to make and well worth alot of time. Good luck with your pyrotechnics and play safe, common sense and a good head is needed.

Thanks for saying that Karl, I was going to say the same thing. As the mix gets wet, it could result in the classic nitrate/aluminum reaction, beyond wrecking itself for any effect.

[Rhodri]

Guys - good replies re: AN and moisture incompatibilities etc.

However, the 'landlord' would like to call 'time' on this thread.

Thanks.

[al93535]

This is from a skylighter article:

SOUPED UP FLASH

This one from Ed Defoor. Thanks, Ed.



?I thought I told you about my mixing black powder with flash. I find it doubles the boom. I mix 4fg about one to two of flash. In smaller crackers, I grind up the 4fg and mix it about one to two also. I think the increase in bang is probably because the flash is fluffed up, so to speak, but in using meal powder, I think the sulfur content also adds to the enhancement of the explosion. However it works, the addition of black powder does soup up the report.---Ed D4?

Has anyone tried this? I would assume if you were to use corned grain powder the sulfur should be kept away from the flash enough to keep it from becoming more sensitive.

[Frozentech]

Does anyone have any experience substituting -325 Bright Flake Al for -325 dark flake in Ofca flash comps ? I am looking for some 'slow' dark flash as a burst charge booster, about 2 grams added to KP/rice hulls in 3" plastic shells. Something between whistle and 70/30.

The original Ofca formula :

Burst Charge Explosive:
Name: Ofca Flash
Source: Bill Ofca

Aluminum, flake, dark, American dark. -325 mesh - 2
Potassium Perchlorate - 2
Potassium Nitrate - 2
Sulfur - 1
Barium Nitrate - 1
Antimony Trisulfide, Chinese needle - 1


NOTES:
The author states that it is important to use the 809 American dark aluminum, as other types of dark aluminum will make the mixture too hot and cause it to behave like standard flash. The theory here is that droplets of a molten mixture are driven into the stars when the flash ignites, reducing the blind star problem often encountered when flash breaking shells.

[Yugen-biki]

My experiense tells me that dark Al is stronger than bright Al in flash.
If you seek to use it in flash bags, I suggest that you substiute some of the fine flake Al with atomized. Atomized Al is really slow in comparison and forms molten droplets. And there for used in flash bags.
I have little experiense with flash bags but more with flash used as a booster in combination with another charge like H3, KP or BP. And I don't think you will blow any stars blind if you substitute the Al. But it will be much more important which Al is used if only flash is used as burst charge.

[karlfoxman]

The Antimony is used to force molten droplets into the surrounding area, i too use flash only as a booster and in flash inserts. I never had a star blow blind in the few shells i made using it.

[shadowpyro]

Would anyone be able to supply me with an accurate weight ratio and a stoichemetric formaula for an Mg + Al + KClO4 flash powder?(i wanna know this as i have some 400 mesh AL powder and its totally useless on its own, therefore an addition of Mg powder should sensitise it enough to light) For anyone out there id only suggest trying this if you can only get hold of courser mesh Al. Mg flash powder are very powerful and can be very sensitive even if course meshes are used.

thanks

[alany]

You could do the math youself...

Magnesium forms MgO, Aluminium Al2O3. So Aluminium has 1.5 times the molar Oxygen Demand of Magnesium. Hence, to replace a fraction of Aluminium with Magnesium and maintain the same Oxygen balance you have to use 1.5 moles of Magnesium for each of Aluminium. The molar masses of Mg and Al are:

Mg = 24.305
Al = 26.982

This is a mass ratio of 0.901 giving a substution ratio of about 1.351:1 Mg:Al.

So, if you start with conventional 7:3 flash and replace 1 part Aluminium with 1.351 parts Magnesium the Oxygen balance will be preserved. Of course oxygen balance isn't everything, and anything from 1:1 and 3:1 will probably work just fine.

[Rhodri]

Alany, as always, a perfect post with an excellent understanding of pyrotechnic chemistry.

Shadowpyro, may I ask why do you need a hybrid of Al and Mg? Many of the standard ratios for flash are more than 'fit for purpose'.

If your flash is not up 'to scratch' then maybe one should change the pre-cursors?

[gilbert pinkston]

i once did an experiment
made a little magnalium KClO4 flash test
had probably less than a tenth of a gram of perchlorate clinging to the sides of my mortar and pestal threw in some Mg/Al and applied a little pressure not much
POP!!!
it went off so easy
unless i think i cant do without it i will never make it again it is way too sensitive
i would put on my thinking cap and try to improve my aluminum
plain Mg may be even worse

[pyrotrev]

plain Mg may be even worse

Mmmmmm .....on the other hand it might not be. Remember that magnalium is harder and more brittle than either pure Mg or Al, hence forms sharp spiky fragments which are more likely to cause mechanically initiated ignition.