Hottest compound (for igniting thermite)

[dbooksta]

I've had a heckuva time trying to ignite a batch of 500 mesh Fe2O3:Al (8:3) thermite. Magnesium ribbon: fail. Visco fuse: fail. KMnO4/glycerol: fail.

 

I think it's common to use "sparkler" compounds (if not actual store-bought sparklers) to light these. Does anyone know which recipes burn the hottest, for purposes of igniting thermite? E.g., between KNO3/sugar, KClO3/Al, KClO4/Al? Exotics that burn hotter would be interesting to note even if not practical depending on current supplies.

[wyzard10]

Ive always used sparklers to light thermite i stick 2 or 3 of them side by side about half way into the mix and light them and run like crazy. They act like a visco fuse in that you get some time before it lights the mix. Do you research on what your mixing up before you do it. Some of the the exotics you mention can react far more violently than the aluminum/iron version. Not fun to have molten metal flying around all over the place.

[dbooksta]

So which mix is used in consumer sparklers?

 

(Also, I meant exotic ignition recipes, not exotic thermites.)

[Seymour]

For Fe2O3 thermite using atomised Al I use any hot burning comp, usually a MgAl fuelled star.

 

For Fe3O4 thermite I tend to light it with Fe2O3 thermite.

 

With dark flake Al, bot CuO and Fe2O3thermite light from black match

[Nessalco]

A reliable electric igniter for thermite can be made with a 50:50 slurry of cupric oxide and -200 graphite, bound with NC lacquer. Strip 1/4" of insulation off standard shooters wire, dip in the slurry, and let dry (no bridge wire). These require 12v to work, but they create an intense heat and droplets of molten copper, which lights all forms of thermite I've tried it with.

 

Kevin

[Sparx88]

I was trying different things a year a go just to see what else would work and ended up this;

 

P.Chlorate 65

dark/5413 alum 20

black copper oxide 10

parlon 5 (acetone)

 

I imagine if fine magnal or magnesium were subbed for the alum it would light it up nice. I don't use magnesium and the magnal I have is too coarse or I woulda. I used to use a different mix almost like slow flash but this worked faster.

What I do is form a 1" cube around the end of good 3/32 visco. The parlon is used only so I don't use water that could screw up the fuse while the comp dries on it. Good luck on getting it figured out.

[taiwanluthiers]

I've had a heckuva time trying to ignite a batch of 500 mesh Fe2O3:Al (8:3) thermite. Magnesium ribbon: fail. Visco fuse: fail. KMnO4/glycerol: fail.

 

I think it's common to use "sparkler" compounds (if not actual store-bought sparklers) to light these. Does anyone know which recipes burn the hottest, for purposes of igniting thermite? E.g., between KNO3/sugar, KClO3/Al, KClO4/Al? Exotics that burn hotter would be interesting to note even if not practical depending on current supplies.

 

I have had success by using a 50/50 mix of potassium perchlorate and 325 mesh spherical aluminum. It burns very hot but not really fast.

[dbooksta]

 

I have had success by using a 50/50 mix of potassium perchlorate and 325 mesh spherical aluminum. It burns very hot but not really fast.

Does the excess Al slow the burn rate? Or do you have to mold it with some other compound to keep the rate down?

[Seymour]

The problem with 50/50 KP /Spherical Al is how hard that is to light. This is why I use coloured stars (and convenience). Adding 5-10% Organic fuel will help with ignition of the igniter.

 

My guess is the 50/50 ratio burns slower and gives off more sparks and solid/liquid stuff in the immediate area because less are dispersed.

 

Anything with main oxidiser KClO4 or KClO3 will work with 5-25% organic fuel and 10- whatever Al/MgAl/Mg

With KNO3 you just need more metal, upwards of 30% should work.

 

But it does help to add the organics to make the igniter more ignitable.

 

I am only talking about thermite using medium atomised Al and Fe2O3 or CuO. Fe3O4 is another story, and things change with Al particle size, obviously.

Edited August 24, 2016 by Seymour

[taiwanluthiers]

I only done it in trial quantities... what I did was place thermite on the ground, and a small amount of the 50/50 perc/aluminum mix. I would then hit it with a blowtorch until it ignited. Thermite will not ignite from blowtorch at all. I cannot comment on how fuse sensitive 50/50 perc/aluminum mix is since I have not tried to use it that way.

[Redrocketman]

Regular RIO thermite has lit every time using 2 or 3 sparklers with the bottom half wound with Mg ribbon. Have also added a good pile of KCOI4/Su on top sometimes, just for good measure! I like a bit of time to move from the immediate area!

[dbooksta]

A reliable electric igniter for thermite can be made with a 50:50 slurry of cupric oxide and -200 graphite, bound with NC lacquer. Strip 1/4" of insulation off standard shooters wire, dip in the slurry, and let dry (no bridge wire). These require 12v to work, but they create an intense heat and droplets of molten copper, which lights all forms of thermite I've tried it with.

 

This has worked well on loose thermite. I'm not sure why, though -- when lit in isolation these electric igniters don't produce more than a nearly instantaneous and apparently miniscule squirt of sparks.

 

But one test I've been trying has pressed Fe2O3 thermite into an iron pipe and I haven't found anything that can ignite that! Even when it's pressed around one of these CuO igniters.

[NeighborJ]

Dbooksta, the loose thermite ignites because the particles are not in enough contact with their neighboring particles to create much conductive heat transfer. This allows the reaction to take place on the surface and spread, regardless of the compositions temperature.

The pressed thermite will conduct the ignition heat away from the point of application too quickly which prevents the surface from becoming hot enough. The only go around would be to ignite a loose pile on top of the pressed thermite but even this may fail if the loose pile is too small. It will need to be a large enough pile to add heat to the pressed thermite quicker then it can conduct it away.

[OldMarine]

I've been wondering and this seems to be a good place to ask: What is thermite used for in pyro?

[dbooksta]

Dbooksta, the loose thermite ignites because the particles are not in enough contact with their neighboring particles to create much conductive heat transfer. This allows the reaction to take place on the surface and spread, regardless of the compositions temperature.

The pressed thermite will conduct the ignition heat away from the point of application too quickly which prevents the surface from becoming hot enough. The only go around would be to ignite a loose pile on top of the pressed thermite but even this may fail if the loose pile is too small. It will need to be a large enough pile to add heat to the pressed thermite quicker then it can conduct it away.

 

Makes sense. I'm going to try to build an ignition train for pressed thermite -- e.g., electric CuO igniter to loose Fe2O3 thermite in a tube inserted in pressed thermite. (Why? I don't even remember if I had an application for pressed thermite in mind. But then it went and made itself a challenge )

[NeighborJ]

I can completely understand the fascination with thermite. The few times we've used it at work, we ended up playing with it afterwards. It's just a cool science experiment.

I've seen it used in comps as part of the formula. The winokurs have it and I would guess it smooths out the burn so the sodium bicarbonate doesn't strobe. Or to keep the heat of combustion close to the star surface during flickering. Just a guess thou.

[Nessalco]

I've been wondering and this seems to be a good place to ask: What is thermite used for in pyro?

Not a darn thing, OM. Still, it is an interesting group of comps and interesting to experiment with.

 

Some folks in the high-power rocket crowd use copper thermite to assist in the ignition of large motors.

 

KO

Edited October 11, 2016 by Nessalco

[Maserface]

I've been wondering and this seems to be a good place to ask: What is thermite used for in pyro?

Most hot primes utilize thermite in some way, its very useful in that application. I think crackle formulas can ask be considered thermite.

 

But raw loose thermite? Not really useful for us

Edited October 11, 2016 by Maserface

[dbooksta]

Here's an explanation of how copper thermite can be used to optimally ignite solid rocket motors.

 

Also, anytime you need molten iron and you're not near a blast furnace. Which may not be too frequently....

[OldMarine]

Here's an explanation of how copper thermite can be used to optimally ignite solid rocket motors.

 

Also, anytime you need molten iron and you're not near a blast furnace. Which may not be too frequently....

I've welded overhead crane track with thermite and may have ruined an aluminum engine block with it but didn't know there was a pyro use.

[dbooksta]

I've welded overhead crane track with thermite and may have ruined an aluminum engine block with it but didn't know there was a pyro use.

 

Hmm... pyro use: So you've never needed an overhead crane to position your mortar banks ... after melting the engine block on your forklift?

Edited October 12, 2016 by dbooksta

[MrB]

 

So you've never needed an overhead crane to position your mortar banks ... after melting the engine block on your forklift?

 

I think it's more along the lines of wanton destruction of forklift engine, and work-welding crane. I've welded railraod tracks with thermite. But for "pyro" i sort of come up short, when trying to justify it's use. Well, unless you count "light shit on fire, and giggle like a 7 year old", which just might be reason enough on it's own.

[OldMarine]

The overhead crane work was awesome. It was for an assembly line at a Caterpillar dozer assembly line. Heavy duty 6-1/2' rails.

[Plasmaniax]

You ever tried sulphur and aluminum mix to light it? Maybe silicon/ potassium permanganate fuse?

[Sulphurstan]

What worked pretty good for me is to put a mix of thermit, bp, si and NC on top of the thermit . It lights almost Everytime. Note that I make my thermit only with Al "bronze" (flaky Al used in paint). Will that work with other kind of Al, no idea. Edited September 12, 2018 by Sulphurstan