Testing Reactivity of Aluminum

[Shunt]

OK, I know I may be walking on thin ice here, but I want and need some of the more experienced members to comment in the hope it may keep myself and others "safer" in our hobby.

 

There are SO many varieties of AL out there from different vendors. Slylighter for instance has 5 different flake varieties offered for sale. Not to pick on Skylighter, I have researched vendors for years and they are one of the most respected, and have a great website for beginners to learn and do pyro safely.

 

I know that atomized in what ever mesh/uM size is not as reactive as flake. But there is where I need help. Since the "reactive target" craze started, I started looking at sellers there, and have found good prices, but there is no specs for what they sell. I had a friend who is a gun shooter, not a pyro, bring over a lb of AL he bought at a gun show and ask me...Is this the "good stuff"? It looked like Eckart #5413-H to me, but how the hell do I know?

 

How would you test unknown AL flake, and feel somewhat safe in using it in your comps?

[Mumbles]

Based on density, and often odor, it's fairly easy to tell atomized from flake apart. Most flake varities will be much less dense and fluffier, and often have a stearin coating which has the tell-tale odor of wax/crayons.

 

If it's flake, and dark in color as you describe, it's almost certainly some variety of dark flake. All the dark flakes I've come across will make fine reactive targets. If you have authentic samples of 5413 and probably Eckhart 10890, you can probably differentiate them visually. They're different colors, and 5413 will be denser.

 

It'd be hard to find a good composition to do a test with. The easiest, and probably most telling, would likely be 70:30 flash. I'd want to have some controls of known materials to compare against. Keep the batch sizes small. Atomized will likely be hard to light, and just burn in the open. A dark flake of double digit micron size will probably burn more flare like. Something like 5413 or indian blackhead will burn very rapidly.

[Shunt]

Thanks Mumbles, good info as usual.

 

My old 5413 is long gone, but I do have a couple varieties of single digit micron that work well in 70/30, one a bit better than the other I will get a sample of my friend's new stock and do some unconfined burn comparisons with the same KClO4. I noticed you used the word "density" twice in your reply. That got me thinking. I might first fill a small container to the brim with each sample, being careful to handle each with care and not unduly consolidate the contents by tapping or other mechanical means. Then weigh the contents of each on an accurate scale. That might give me some rough numbers to determine the "fluff factor" so to speak.

 

I am an old measurement and metrology technician by trade, but mainly worked with systems that measured natural gas, water, and tanker truck weights by the millions of cubic feet, millions of gallons, and tons. Never had much lab experience in the small stuff except for pressure and temps. There, I could split hairs with the best of them.

 

Honestly I do not have that much experience or interest in 70/30 except in very small amounts used as a booster for small shell break charges. Even then I prefer a variety of whistle mix booster, as then I at least have some reasonable assurance of repeatability in the future. With 70/30 the outcome all depends how reactive the Al is.

 

Sorry if I got off topic a bit, maybe this thread should not even be in the Safety section of the forum, or even this forum at all. I am mainly trying to keep a old and dear friend safe, and keep him from sticking his head into a five gallon bucket full of N2H4O3 and mixing unknown Al into it and getting his ignorant ass as well as the others around him maimed or killed trying to outdo others on the rifle range.

[FlaMtnBkr]

Mixing with KClO4 is probably a pretty good way without a decent microscope. My 325 mesh atomized won't burn in the open much less explode in a tube. Though in enough mass and with enough heat it might. Unless it's very small micron atomized which isn't very common.

 

But all that doesn't really matter because 325 mesh atomized is all that's needed to sensitize NH4NO3 for exploding targets. Since it goes high order and isn't deflagrating or burning fast like flash powder a small particle that will burn super fast isn't needed. I have tried a lot of different aluminums and as long as it's about 300 mesh or finer it will work.

 

Since this is in the safety section, I really hope your friend isn't shooting at 5 gallon buckets full. That is over 40 lbs and enough to hear a few counties away and will level a house. Heck, a lb is enough to hear a few miles away through woods.

[Richtee]

About 300 grams will dis-assemble a washing mahine too

[FlaMtnBkr]

200 grams will cut down a 4" pine tree it's hung from and will remove about a foot section of a 3"-4" fence post.

 

Supposedly 100 lbs blew the bed of a large dump truck (Probably more than a few tons) a quarter mile away and got a LOT of unwanted attention.

[gregh]

The mythbusters made a concrete truck disappear with it!

 

https://www.youtube.com/watch?v=Gxm_qpKh7Jw

[Shunt]

Thanks for the replies guys.

 

It is indeed a very powerful comp. That is why I was trying to find out what my friend bought and compare it to what the commercial vendors use. I seriously doubt that they use single digit micron after the comments above. Just wonder about the sensitivity if single digit micron was used. I sure don't want to try it.

 

PS - The "5 gallon bucket" comment came to mind after seeing a Youtube vid of some 'Billy-Bob-Gobstopper' doing just that with airfloat Al flying all around without so much as a bandanna wrapped around his snozzle. Not that it would have helped him much if a spark decided to take interest in the experiment

[FlaMtnBkr]

NH4NO3 is actually a fairly lazy oxidizer and probably wouldn't do much especially in the standard 95/5 ratio that is so oxygen rich. It probably won't burn much less act like flash powder, even in a optimum ratio with far more aluminum than will be used for exploding targets.

 

Exploding targets are now sold in chain stores all across the country. Any yahoo can walk in and buy high explosives. They wouldn't be allowed to do that if they weren't fairly safe to mix and handle. If there was a chance a spark could cause an explosion they wouldn't be sold. Even with very fine reactive aluminum, the only way to cause an explosion is with a high velocity shock from a bullet or blasting cap.

 

He should be safe as long as he doesn't do anything stupid when shooting it.

[MrB]

The mythbusters made a concrete truck disappear with it!

 

They used "commercial blasting agent", but in the episode they don't specify exactly what, only that it's used for quarrying. Now, that's nothing KClO4 based, thats ANFO. In later episodes they refer to it as ANFO as well.

Now, i'm sure you could make a cement truck go away with KClO4 based explosives,, but i don't know of it ever being done.

 

For quite some time that failed shot of the cement-truck explosion was the biggest explosion on tape Mythbusters had, but they beat it when they went and made diamonds. And they got a highspeed shot of it to boot.

Yet, the cement-truck explosion remains the most popular one. Weird, but i think it's about the scale of things. A drum of whatever that explodes, vs a truck going away. A lot easier to get a sense of whats going on with a "known" object, and everyone knows what a cement-truck looks like... Guess were stuck with watching the frame by frame stills of the cement-truck vanishing trick.

B!

[Shunt]

NH4NO3 is actually a fairly lazy oxidizer and probably wouldn't do much especially in the standard 95/5 ratio that is so oxygen rich. It probably won't burn much less act like flash powder, even in a optimum ratio with far more aluminum than will be used for exploding targets.

 

Exploding targets are now sold in chain stores all across the country. Any yahoo can walk in and buy high explosives. They wouldn't be allowed to do that if they weren't fairly safe to mix and handle. If there was a chance a spark could cause an explosion they wouldn't be sold. Even with very fine reactive aluminum, the only way to cause an explosion is with a high velocity shock from a bullet or blasting cap.

 

He should be safe as long as he doesn't do anything stupid when shooting it.

Thanks for the reply.

 

I know commercial targets instruct the user to open the packet of Al, dump into the plastic container, close container and shake. There should be very little risk of "flash fire" if those instructions are followed, especially outdoors.

 

My concern was not about an explosion, as I know that is almost impossible, but a "flash fire" from the cloud of airborne Al when mixing large amounts. Sorry I was not more clear in my question.

 

Thanks again for all the replies!

[gregh]

NH4NO3 is actually a fairly lazy oxidizer and probably wouldn't do much especially in the standard 95/5 ratio that is so oxygen rich. It probably won't burn much less act like flash powder, even in a optimum ratio with far more aluminum than will be used for exploding targets.

 

 

 

I agree and disagree... Yes, it might be hard to light and not want to deflgrate which makes it seem lazy, but put a blasting cap and a booster in it and it will detonate in a hurry (not lazy).

 

They used "commercial blasting agent", but in the episode they don't specify exactly what, only that it's used for quarrying. Now, that's nothing KClO4 based, thats ANFO. In later episodes they refer to it as ANFO as well.

 

Yeah I know they used Anfo, an ammonium nitrate/fuel oil mixture typically with a 94/6 ratio, but they were discussing AN mixtures so I thought I'd throw that funny clip in there.