Testing of unknown explosives

[chemoleo]

Hello all,

I am going to try out a number of peroxides and organic nitrates and more over christmas holidays, if there's enough time for all this.
If it works, I will give you proper details of the compounds made.
For starters, I'd like to know how I should best go about that.
Obviously I start with small batches etc, to limit any damages of runaways/overly sensitive compounds.
Let's just assume I manage to obtain a liquid/solid that doesnt blow up while drying/mixing/storing it.
1. First test would be heat. A fuse to see how it deflagrates/detonates.
2. Thermite to see how it acts on heat shock
3. The good old hammer test - see if it makes a loud sharp report.

Say, I find they are all between primary and secondary, i.e. a flame doesnt always cause det, thermite does (as I found with HMTD), and hammer does (or does not).

At that point, I would go about evaluating the explosive force.
Thats where I would like your advice:

Say I make a crude homemade blasting cap, primer HMTD, with a bit of the unknown Explosive at the bottom. Preferably not in a metal container, as I wouldnt like to test the sensitivity of peroxides in the presence of metals.
I use a straw or similar plastic tubing, filled with 3 g of HMTD and below the unknown E.
How would I best go about of deciding whether the unknown E. detonated (i.e. I wouldn use a huge exess of primary over unknown E.)
Of course I could do the control, i.e. primary + the putative secondary unknown, and the other time primary + a random chemical, such as sugar. However this would be time consuming, and unless I use a big excess of secondary (i.e. more than 2x as much as the primary), it is hard to judge, i.e. in terms of the amount of soil obliterated.

Basically, I would just like to tap your knowledge/experienece on how I would best go about evaluating explosive force (in relation to other known explosives) of unknown explosives without doing extensive test series, without using heaps of the unknown explosive, and without using fancy equipment (i.e. the ones being used for determining VOD)

Advice anyone?

Thanks, chemoleo

[blindreeper]

Instead of a hammer which isn't constant (type fo hammer, how much you decide to hit it) make a drop test rig. Axt has a brilliant video of his on his website. I am in the proces of making a smaller one. probably only 5g or less explosive could be used and it has a 600g hammer. It is accurate to a cm and goes from 1cm to about 40cm. I hope to test some explosives like this int he holidays aswell.

The good ol' lead block expansion test is very good for measuring explosive power. A lead cylinder with a hol in it is filled with a know amount of explosive and detonated. The cavity it makes is recorded. I have a 6kg lead block which is about 10cm high and 7cm round with a 10mm dia. hole in the center with about 1-2cm space from the bottom of the block. I don't know what I should use in it because it takes a bit off effort and gas to cast a block that size.

The other test for explosive power is aluminium plate test. It involves detonating a know amount of explosive in on an aluminium plate, usually 3-5mm. A good explosive will make a clean hole. They also do this with lead plates.

The is a lot on explosive testing in "The Chemistry of Powders and Explosives" or COAPE if you will. It has detailed explainations on all the things I have mentioned above.
Happy testing. Be sure to take lots of movie and pictures. Its better than reading a bunch of text!

EDIT: Just thinking about your tests, the thermite one isn't very good because if the explosive is flame sensative it isn't very good because thermite produces a great deal of fire.

The heat test as you call it should be called a flame sensativity test. If you have a flame on the end of a long stick and expose the explosive to the flame you are looking to see if it detonates or whatever it does. If it burns calmly it would be counted as not flame sensative or whatever. But taking a movie of it is the best way.

[Axt]

Didnt I just recently start a topic on this :rolleyes:

http://www.roguesci.org/theforum/showthread.php?s=&threadid=3427

[blindreeper]

Sorry Axt didn't even see that thread :confused: Wasted 10 minutes writing up a decent post :mad:

[chemoleo]

Thanks guys.
What I meant by the thermite test is that I'd use that once the ordinary flame test failed.
Sorry for partial overlap Axt.
What I was looking for specifically is to test as many variables of an unknown explosive with as little explosive/machinery/material/effort and money of course as possible. Yepp, the cheap and easy way :)

I am aware of the lead block expansion test, but as you say yourself, it's a pain melting 6 kg of lead just for one little experiment!

The Al plate test (in my case copper) seems like a nice and easy one, and conditions could be controlled easily...from the sound of it. Still it needs the control though.... an the other hand, there is no such thing as absolute power if you have no means to compare it to a lesser one!

If my ideas work, and if they seem promising, maybe then I will embark upon making more complicated devices....
Basically, what I am worried about is that I wouldnt be able to tell apart the force of primer alone (i.e. 3g) and that of primer and unknown explosive together (so 6 g in total). I.e. shrapnels etc will give some measure of an additional force, but not a definite one!

I guess the only reall way to do this is to use a huge excess of 2ndary vs primary :(

[Anthony]

So what explosives are you going to be making?

"a flame doesnt always cause det, thermite does (as I found with HMTD)"

Are you saying that HMTD is not flame sensitive? Because I can assure you that it is!

A flame sensitivity rig could have a mini gas torch on a pendulum arm that swings back and forth over a sample of explosive. The greater the number of swings before the same decomposes, the higher the flame sensitivity.

[Axt]

Now if this wasnt in the watercooler it might be worth replying too.:mad:

Anthony: Or the slower the swing the less sensitive to flame (slower the longer it will be in contact) adjust the swing by moving a weight up and down the pendulum, or is that what your getting at anyway ... the longer it swings the slower it gets.

Blindreeper: We posted at the same time. For a smaller drop test rig you will want a pretty small diametre "hammer" to increase the pressure on the explosive, probably about 8mm diametre should work with that weight. You will use a lot less then a gram of explosive with this, you only want a thin layer of explosive spread over the entire area the hammer will strike. The movie of mine shows more then that but that was just for the movie.

You would likely be best off using a hardened steel hammer onto a mild steel base, this is so the mild steel will conform to the shape of the hammer so that you will get even hits all the time

[chemoleo]

Ok, somehow I don't seem to be getting it across :( - didnt think my communication skills were that bad! Probably everyone thinks being a newb on the forum equals dumb, so the worst is naturally assumed :D:D

I wont tell yet whwat I am going to test, simply because I dont want to get anyone excited about it until I get results, for it might fail to start off with. Just like in research in ac. science (personal experience :) ). It wont be anything thats been discussed on this forum :), but it wont be a sensational new idea either... just expanding known principles :). Lets just hope I get enough time over Christmas.

On HMTD - to my experience, and to others (a few had the same thing), it burns violently when exposed to flame of course, this is when unconfined (like nitrocellulose). The only way I found to detonate it reliably, WITHOUT any confinement at all, was if I layered a small amount of thermite on top (in a film capsule), whereby the molten Fe/Al2O3 would drop onto the HMTD. This way I avoid pressing etc, which I like because I value the function of my fingers...

Back to testing explosives.
I figured that flame test with varying heats (pyro mixes, match flame etc) would tell me the flame sensitivity, in very crude terms. Then there are two possibilites:
1. It doesnt burn - because the explosive is crap/not really an explosive at all, or because it can be only detonated. Like some aromatic explosives, which just slowly burn, but with massive shock, explode. In any case, as I wont know whether the explosive is a functional one or not, I have to use the shock method. Hammer is one, whcih may not produce results, however. At that point I would also use thermite, to see whether heat shock & instant evaporation would cause det. (as with HMTD in my case)
2. It deflagrates, say like HMTD. Then I would try the hammer & thermite, too. If I achieve det. easily, I would play with it a little more at that stage, as it then would be a member of the primary explosives.

Let's assume it doesnt deflagrate, and I cant set the unknown E. off with either flame, thermite, or hammer. I will need to test it with a primary. And here I am not so sure as to how I would tell apart the force of the primer alone and that of primer & unknown explosive (u.e.) together, especially if I dont use an excess of primer vs u.e.
I wondered how it would be *easiest* to tell the difference.
I don't particularly fancy making larger amounts of u.e. just to make sure there is a difference. Any ideas? So far I am most in favour of the metal plate method, by the dent/hole etc produced I might be able to tell. ..


PS I like your hammer method :) Sadly though that doesnt provide a measure of the explosive force, right.... I was more after evaluating the latter :)

[Bert]

If you want to measure relative force, try a balistic pendulum.

[blindreeper]

Axt, I found the steel bar I was using in the rig didn't make match heads go off, so i got a wheelie bin axle (1.5kg) and they have a taper on the end. So they are about 3/4inch round and taper to a 1cm flat surface. That sets of match heads, but when I cut the other end flat it didn't go off, so your theory is correct :)
I am using a 3mm thick pice of square mild steel as the plate.

Chemoleo, if you have large quantities of HMTD is will detonate. Also thermite isn't a reliable test I don't think.