43 replies to this topic

[bigtonyicu]

No worries… I'm OK somehow…

KIDS THAT WHY YOU DON"T MESS WITH FLASHES and WHY YOU USE A VERY LARGE SHEET WHEN YOU MIX THEM (36x36 inches) other wise… I'd be more then likely be without a hand.


Due to the difficulties of obtaining KClO4 in Canada most of my flash use KNO3 and KClO3, I have a very small supply of Eckart 5413 and for most of my flashes I use flake 400-mesh, I try to avoid the chlorate based flashes as much as possible (but NEVER had any problems with them. Just treat it like a live, primed high exp. and FEAR it; you SHOULD be safe).

I was trying a composition of my own and it Auto Ignited any clue what happen

67% KNO3
24% Al (400- mesh)
4% Lamp Black
5% Sb2S3

(Basically a 70/30 Nitrate flash w/ Lamp black for IR absorber and Antimony trisulfide for a sensitizer)


Procedure used:

Diaper mixed Potassium nitrate and aluminum (50 folds)
Added lamp black (50 folds)
Added antimony trisulfide a few folds and BANG (Sorry… it scared the crap out of me…. I lost count of the folds on that one)

I use butcher paper plastic side up

Any clues what happened… I know there was no trace of KClO3 any where. All new measuring vessel and obviously sheet.

On the plus side… if I can fix it… WOW did that have power, I only did 5g and it had more kick then my Eckart with chlorate.

Any feed back would be appreciated.

Edited by bigtonyicu, 02 September 2008 - 05:18 PM.

[wjames]

i remember seeing a very similar composition, but it included 2% of boric acid.......

[bigtonyicu]

i remember seeing a very similar composition, but it included 2% of boric acid.......

Might be worth trying, I've never seen a Flash comp. using Boric acid, I thought the acid would reduce the reaction rate

[Bonny]

I don't think boric acid will do anything for you as it is added to Al/nitrate comps to prevent a reaction when wet.
The comp may have ignited from static, and the plastic on the butcher paper could have contributed to this. In any case, the comp is obviuosly much to sensitive to continue working with.

I've read to stay away from plastic when working with flash powders. I use newspaper personally when diapering (bonus no cost). I've never actually counted how many folds I do but probably around 15, or no more than 20 for sure.

[portfire]

First-bigtonyicu I'm glad your ok and you've come away from this experience unharmed.

Now I'm no expert, but this doesn't sound like a NO3/Al reaction. Is it possible that adding Sb2S3 sensitized the comp and maybe friction, static caused the ignition?

The only flash I make is KNO3/S/Al and I always add 1% boric acid, bear in mind I've only made around 20g in nearly 3 years of practicing the art.

[dr thrust]

agreed, adding an excellerant like sulfur/ antimony ect will make the comp very friction sensitive a tiny sub gram amount under pressure pops violently

Edited by chris m, 02 September 2008 - 10:48 PM.

[MDH]

Well he said it was spontaneous.

although I agree with everyone else here, the trisulfide is probably responsible. I HAVE NEVER had a spontaneous reaction with nitrate/al compositions.

[bigtonyicu]

Actualy I never gave the paper any thought, but it could act to creat a static charge that when conducted in the Sb2S3 might create enough of a hot spot to ignite... I'm going to add 1% boric acid and mix on kraft... see what happends...

I've made several 100gs if not kilos of flash over the years on that paper and never had any reactions like that kind of scary looking back on it... let me mix up a new batch and see...

Edited by bigtonyicu, 02 September 2008 - 08:43 PM.

[pyrotrev]

Actualy I never gave the paper any thought, but it could act to creat a static charge that when conducted in the Sb2S3 might create enough of a hot spot to ignite... I'm going to add 1% boric acid and mix on kraft... see what happends...

I've made several 100gs if not kilos of flash over the years on that paper and never had any reactions like that kind of scary looking back on it... let me mix up a new batch and see...

Almost certainly the paper IMHO - plastic both generates and stores static. What was the weather like? Both the sheet and powders will be much more likely to generate static if they're really dry.

[Bonny]

I'd ditch the butcher paper and watch the relative humidity as pyrotev mentioned, minimum 50%.
I really see no reason in wasting your time adding boric acid as I don't think it will do anything to prevent this from happening again.
See here for more safety tips: http://www.apcforum....?showtopic=2852
There is someone on APC who mixes by GENTLY pouring between 2 paper cups (no plastic).

[bigtonyicu]

Well the weather was very humid, in the 70-80% range (like every day in Ottawa sticky muggy awful summers).

As for the paper I'll just use it plastic side down as a bench protector.

I say plastic, but it could be a wax coating I'm not sure, it's standard red kraft butcher paper (the coating is there to make it water proof)

I mixed a 2g batch last night (on brown kraft) and this time nothing, I split the batch in 2; I'm leaving one half sit for 1 week (stability testing) the other I drop tested (impact test) last night up to 2m with a 10KG weight (max my remote rig can handle) and NOTHING. I manage to recover 0.6g off the anvil and thought the best way of disposing of it was to light it... VERY impressive. So if the 1 week turns out good. It’s a very powerful flash but it is highly static sensitive.

[Bonny]

It’s a very powerful flash but it is highly static sensitive.

Then why bother? You learned first hand that it is obviously not a good comp to work with. For safety's sake, I'd toss that comp into the "tried and failed" list.

[pyrotrev]

Or keep it for in container mixing - IMHO by far the safest way to mix flash.

[Creepin_pyro]

Or keep it for in container mixing - IMHO by far the safest way to mix flash.

I'll second that! No need to diaper if you're tumbling the finished units remotely.

[wjames]

that was suggested to me.....using paper cups, of the type without a lining...like you see on water dispensers.....

seems a sensible idea to me.