Cast Thermite

Step 6: Casting

Picture of Casting
This is it! The final step!

Take that nice gooey thermite that you worked so hard on and carefully slop it into whatever you are using as a mold. This ice cube tray worked very well as I wanted something small and reusable. Since the shape of the ice cube tray is larger at the 'bottom' I didn't have any trouble removing the cubes.

Keep in mind how the thermite will harden inside an object when you are deciding what you want to use as a mold. Something like a bottleneck vase for flowers would never work unless you planned on breaking the vase off of the cast thermite once it had dried.

Once it has solidified, (it should only take about a half hour to 45 minutes to), pour off the water and remove it from the mold. According to the anarchist cookbook, these will have to dry in the sun for a week, more or less depending on the size of the cast. Alternately you can place them in a oven or dehydrator to dry them much faster, probably in a matter of a few hours, which is the method I use.

Whatever you do, dont put them in your microwave. I doubt they would ignite, but as they are basically chunks of metal, I don't think your microwave would appreciate it. Once again, I'm not liable! Be smart!

As for ignition, thermite requires extremely high temperatures. If it was normal powdered thermite that we were talking about a magnesium sparkler would do the trick, but not for cast thermite. This requires something like the heat from a propane torch, (don't try it, you would have to be far too close to ignite it.) I use something called First Fire Mix. Google it or check back in the near future, as my next instructable will be on making a basic igniter for thermite.

That's it, you're done! If you need any help, check back or comment/pm me, I would be more than happy to help. This is my first instructable, so let me know how I did!

*Edit* For those of you who still need help lighting thermite and other difficult to ignite materials, check this out.

Enjoy your new cast thermite!
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Would it be possible to simply just stick a 10 cm or so length of magnesium ribbon in each cube while they're setting?
Joelsefur3 years ago
You have no idea what your doing. Ground aluminum foil, burnt steel wool, and a propane torch does not make thermite. Those materials would never combust in such a raw form and from such a small amount of heat. Even if you got this to ignite it wouldn't be much more than a little light and fire. It wouldn't even compare to actual thermite.
Zlwilly (author)  Joelsefur3 years ago
Really? Hmm. That's strange, have you actually followed the instructions and tried it. It works perfectly for me. Bright, hot, and altogether thermite-y in nature.

All due respect, from personal experience doing this countless times, the materials definitely do combust ferociously. Simply put, you're incorrect. But don't take my word for it. Try it for yourself. :)
wizodd5 years ago
This is NOT a good idea! It will work well with fairly course aluminum, but aluminum powder gets touchier and touchier around water as it gets finer. A mix of very fine (100mesh&finer) can ignite by getting damp. This risk is higher with ultra fine (black) aluminum, and the addition of magnesium will increase the likelyhood. The resulting cubes will burn a little cooler because they will use up some energy to turn the plaster back into powdered (anhydrous) form--though probably not noticeably so. The addition of sulfur to make thermate, also lowers the ignition temperature to well below the melting point of aluminum. It is not a good idea, for the same reason, to keep mixed thermite powder on hand--moisture can set it off spontaneously (it is also illegal in many places.) Always store fuels (like aluminum) away from oxidizers (iron oxide) in cool dry places. There are a number of different formulations for termite and related incendiaries. Some are designed to cut, some to weld, some to set fires. It won't normally explode, but if you contaminate the mix with other things, anything can happen. A little bit of a stronger oxidizer might cause part of the batch to explode--sending molten iron spraying in all directions. Such a device could be made by surrounding a small HE charge, or even a glass vial of water.... One thing that the mixes can do is put out a LOT of heat in a very small space in a very short time. In or under water this makes a spectacular (albeit dangerous) show. Most such experimentation should be done at a good distance. Be careful about setting it off on the ground too...if you have a porous rock and it hits the molten iron, it may explode if it has any water soaked into it.
hogey74 wizodd3 years ago
Yeah be careful with this stuff - molten iron goes straight through clothes and human tissue and its only half the temp of Thermite! I'm as in favor of burning and blowing up stuff as the next man but the quick refresher I just gave myself via google reminded me how careful you have to be with thermite. You could probably burn a hole to the center of the earth with it. Which would be pretty cool actually ...
Zlwilly (author)  wizodd5 years ago
Yes, moist aluminum is more likely to ignite. (Weird, huh?) However, a slurry of aluminum, iron oxide, and plaster of paris has never burned my house down. Yes, this isn't quite as potent as regular thermite. But it is still pretty interesting, in some cases more so that the powder alone. (If you still believe that thermite can burn through an engine block, please try it for yourself. It's nowhere near the first time that a commonly known fact has been VERY incorrect.) NO one added sulfur to thermite. At least not in my Instructable. I'm not making flash powder here, please read the whole instructable in its entirety. Don't keep mixed thermite on hand? Assuming that's true, it's a good thing I don't. Assuming it's not, are you SURE you aren't confusing the safety precautions of flash powder with thermite? If you meant some of these points (such as the salver comment) to be a general statement, rather than directed at this Instructable, my apologies. ;-) The last 2 points you made are very good, thermite does have some interesting reactions with water! My main point being that experience has led me believe that this is a perfectly safe experiment to perform. Thanks to your warnings I may be a little more wary, but until I have reasons to believe otherwise, I will continue with my thermite excursions in the same manner. Cheers!
Engine blocks are made from either cast iron (melting point = ~1200 C), aluminum (mp = 660 C), magnesium (mp = 650 C), or an alloy of the latter two.

Considering that:

A: Thermite is used to weld things like railroad tracks (which are made of steel that's far thicker than any part of an engine block) together.
B: Thermite burns at around 2500 C, hotter than the melting points of all the aforementioned automotive engine block materials.

I would wager that a large quantity of thermite would indeed burn through an engine. However, I grant you that it would have to be a very large amount of thermite to burn through the block of anything bigger than that Peugeot piece of trash :D
sethzor3 years ago
Dear reader this is also illegal in some states try at own risk.
qwerter5 years ago
To ignite it you could take some magnesium ribon and coil it around a pencil. then place coil in mold with thermite leaving a bit out for a fuse. light then run!!!
Doesn't Mg as well as K react with small amounts of water? How would lithium act in place of FeO3? Would doing some of this in a container sealed filled Helium allow for a more powerful product? Also my chemistry is many years rusty but don't you have a bit of an exothermic reaction with the plaster of Paris?
SeverinR4 years ago
where can you get mag ribbon?
44455 years ago
i got this camp stove stuff they get rely HOT will that work
snipegoat5 years ago
now only if we could do half a mold, dry it, then put a little something extra ; ) in the pour on another layer, for some pop when the thermite burns to the center
comander015 years ago
Great way to light would be like like qwerter said, but instead of miking a coil, insert the magnesium when the thermite mixture is still goopy, making a 'thermite popsicle'.
wizodd5 years ago
Oh, yah, microwaving would quite definitely ignite these, no problem. At a guess, probably well under 5 minutes--ymmv

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