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Hon1nbo

Mon Feb 03 2014, 10:41PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

All,

I have been trying to make a Thermite "brick." I don't like measuring raw powder every time I destroy a drive or cast some metal, so I'd like to make some standard size cubes or similar of thermite.
So far I have looked at some various recipes online, most of which involve plaster of paris. I tried a plaster cube, and I could not for the life of me get the cube of thermite to ignite, even with powdered thermite burning on top of it!
I'm thinking that the various binders are preventing an interaction between the iron oxide and aluminum powder.

Does anyone here have some suggestions for making a solid piece of thermite? Are there any binders that won't prevent the oxidation of the aluminum at a reasonable (relative to normal thermite) starting temperature?

-Jimmy

Shrad

Tue Feb 04 2014, 06:47AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

parafin

I'd wet the mix with liquid paraffin and stirr till it has the consistency of a paste (inside a bowl placed in a container with very hot water so it doesn't solidify, like you'd do with rocket fuel but at a lower temperature)

Sulaiman

Tue Feb 04 2014, 01:13PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

I've never played with thermite but Chemistry used to be a hobby of mine,
I would think that ready-mixed thermite has a risk of spontaneous combustion if moist/damp, which could be disasterous.

Shrad

Tue Feb 04 2014, 04:00PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

hence paraffin, and a poper mix with glycerin or something might event make it plastic

Wastrel

Tue Feb 04 2014, 05:53PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

Anything that produces volatiles is going to be a problem. I would bake the oxide, mix when cool and portion into heat seal mylar bags. They will have a lifespan, but then all aluminium powder goes bad eventually.

Hon1nbo

Wed Feb 05 2014, 06:22PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

Sulaiman wrote ...

I've never played with thermite but Chemistry used to be a hobby of mine,
I would think that ready-mixed thermite has a risk of spontaneous combustion if moist/damp, which could be disasterous.

Well, I tend to use coarser powders that require more ignition resources, though admittedly I did try some finer powder for this when the first batch failed. Nice thing about standard thermite is that unless you have ultra-fine powder it is very hard to light, which makes it relatively safe to handle (key word relatively).
I have never heard of it being more dangerous damp except when actually burning at which point it is practically explosive, but I always treat my thermite reactions like they might explode after a rock that was obscured under a batch fractured violently and caused a serious problem. Also, by the time I intend to light these they will have been dried out.
Is there a particular effect on standard thermite when wet that occurs when not already under ignition conditions?

@Shrad

I might have to try paraffin in my next batch.

@Wastrel

As for baking, I'm not sure how that would work. Does the oxide exhibit some kind of cohesive properties when heated? would it stay intact when cooled? Now that you mention mylar bags I could use a bag that evaporated off.

-Jimmy

Sulaiman

Wed Feb 05 2014, 08:27PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

What kind of bag wouldn't evaporate off with thermite ?

I have no specific. info. on thermite/damp, just that air+moisture = electrolyte between reactive molecules.

Wastrel

Wed Feb 05 2014, 08:35PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

Baking just to dehydrate the oxide. I understand volatiles make the reaction badly behaved.

Shrad

Wed Feb 05 2014, 09:17PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

baking can be the starting point for dropping some paraffin and gently stir till it becomes pasty, then mold in some yoghurt pots or something...

radiotech

Mon Feb 17 2014, 09:20PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

I don't know why you want a brick of Thermite, so I am assuming is it to hold or mold a charge
to a task.

I used to construct copper ground networks out of 000 GA bare stranded wire.
The powder was poured into graphite molds which came in various shapes , X, T, Join,
or Face Bond (to weld the wire onto an iron surface)

The blocks were about 3 x 3 x 7 inch, had a handle, and a hole in the top to ignite.

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