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I'm trying to do a thermite reaction with rust and aluminum and am trying to figure out the optimal way to get the reaction started. My understanding is that I need a temperature of around $\pu{3200 ^\circ F}$ to start it. I am currently aware of two methods to achieve that:

  1. Potassium permanganate and glycerin: But apparently this requires an ambient temperature of $\gt \pu{70 ^\circ F}$, and it's winter where I live, $\pu{40 ^\circ F}$ at most some days.
  2. Magnesium strip: But this requires a blowtorch (trying to avoid buying a blowtorch) and I've read is unreliable for starting this reaction.

Does anyone have any alternative suggestions? Has anyone done this before? All suggestions are welcome.

I am aware of the need to do it far from anything flammable/destructible, and am aware it can damage your eyes, and am aware to keep it away from water and keep my distance. Other tips are welcome.

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    $\begingroup$ I think technically, ignition mixture is used to initiate the reaction which consists of mixture barium peroxide and aluminium powder. But never tried it personally. $\endgroup$
    – An enthusiast
    Commented Oct 8, 2020 at 14:19

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The method I've used is a simple propane torch, which you can get at Home Depot for $14 and magnesium powder. The mixture of powdered aluminium, iron oxide, and magnesium is thoroughly mixed and then lit using the propane torch. It lights all the time with the magnesium embers burning brightly and then the main reaction takes hold. Getting powdered magnesium is cheap as well. Using this method, the reaction takes all the time and I haven't had a single problem with it the numerous times I've done it for an audience.

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"Sparklers" – literally the same pyrotechnic sticks handed to children for celebrations – are what railroad welders use to ignite iron thermite. These are essentially flash powders mixed with a binder to slow their burn rate.

One pyrotechnician created electric thermite igniters by binding a 50/50 mix of CuO and 325-mesh graphite with nitrocellulose lacquer, coating the exposed tips of an unbridged wire pair, and firing it with 12V. I have tested those and found them to work reliably as well.

Another alternative is a small charge of copper thermite (9:1 CuO:Al, using not finer than 325-mesh Al), which can be ignited using fuse or electric match.

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By blowtorch anyway. It is cheap and extremely useful for similar experiments.

Personally, I used $\ce{Al}+\ce{S}$ mix as a starter, that was initiated by blowtorch (note, this mix produces aluminium sulphide that stinks with hydrogen sulfide.) - it is easy, cheap and reliable starter.

Also, a magnesium ribbon can be ignited by common lighter - I did it myself many times by keeping a piece of ribbon just above visible part of the flame for about 15-30 seconds.

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  • $\begingroup$ But will the magnesium strip light the thermite? I have heard it is unreliable. $\endgroup$
    – temporary_user_name
    Commented Feb 5, 2015 at 8:38
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    $\begingroup$ @Aerovistae I successfylly initiated thermite using magnesium ribbon many times. True, it sometimes fails, but mostly because the ribbon falls from the hold. So, yeah, using initiator is better if you need completely reliable option. The initiating mixture composition may be different depending on available chemicals. Also, please note: the easy of ignition is heavily dependent on the particle size in thermite. I recommend the smallest flakes you can find. Also, the rust your are using must be dried, so it contained zero water. $\endgroup$
    – permeakra
    Commented Feb 5, 2015 at 8:46
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My son did thermite reactions for a 3rd. grade science project. We were able to easily initiate the reactions by using commercially-available thermite "fuses" which appear to be regular fuse that is about 2 inches long which then has a small, shiny square of metal about 1/2" x 1/2" and fuse product at the bottom. We just inserted the fuse, shiny metal square into the thermite, lit the fuse, and retreated to a safe distance. We had no problems with failed ignitions, and we got a reliable burn time.

We found sites that sold thermite kits usually had these fuses, as well as small, pre-fused thermite "pots" that could be used alone to create a couple of ounces of iron, or set on top of larger piles of thermite to initiate full-scale reactions. Survival prepper sites frequently sell these self-contained thermite fuses and pots as survival accessories to go along with thermite mix kits.

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You might want to wrap the magnesium ribbon around a sparkler. The latter can be ignited with an ordinary lighter.

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    $\begingroup$ Have you done it this way before? Can you elaborate on how you wrapped it? That doesn't quite make sense to me described so simply. $\endgroup$
    – temporary_user_name
    Commented Feb 5, 2015 at 8:39

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