Copper Thermite Explodes and Smolders Successfully

It was quite a surprise to learn that thermite isn’t just rust and aluminum powder, but describes any combination of metal powder, metal oxide, and optionally fuel mixed together in a reactive ratio.  [sciencewithscreens] shows us some of the properties of a copper (II) oxide based thermite.

We can only assume he has a thing for copper as an element. After growing his copper crystal it wasn’t long before he followed a winding road of copper based experiments and found himself with a supply of copper (II) oxide after rendering it from common household chemicals. He had two missions for it. The first was to witness an unfettered copper oxide based thermite reaction. Some had assured him it was practically explosive. The other was to attempt refining pure copper using the reaction. That would be pretty cool considering it all started out as an impure blend of laundry detergents and fertilizer.

The unrestrained reaction was exactly as explodey as he hoped. The thermite dramatically lit when the electric match was powered on and the reaction was almost too fast for the high speed mode of his camera to capture. Emboldened, he moved onto the thermite refining of pure copper.

Unfortunately the second step wasn’t as rewarding. A mix of too much borax and tamping the mixture down produced a slowly smoldering and sputtering reaction instead of the slow but uniformly hot one desired. He did end up with quite a few nodules of what is likely pure copper, so that’s a win in our book. Video after the break.

25 thoughts on “Copper Thermite Explodes and Smolders Successfully

    1. That would be a worthy hack, but a DIY arc furnace hack seems like a better contender unless you live in a hut on some mountain and have no electricity, but then how did you do the 3D print….

  1. Two thinks, if you wanna slow it the hell down, dilute with copper shavings maybe, or find something compatible that will produce copper or O2 endothermically, sucking heat out, and slow it down.

  2. Yeah… and I hear that sodium metal and hydrogen dioxide works even better.

    But this is not a hack, it is just a good way of making a useless mess and polluting the environment.

    1. It was a good teachable moment for my nephew. I showed him Thermite with a glycerin ignition. After he saw the twisted wreck of the bucket it had been in, and I explained how that could have been him if he messed around with Uncle Tom’s equipment shed, he actually seemed to have a minor epiphany about how bad playing back there unsupervised could be.

      I’m just glad it didn’t back fire. The other option was that he’d start trying to mix everything he could find all at once.

    2. is it this specific method of doing a thermite reaction or the chemistry you find so appalling?

      thermite is used quite a few places in industry, it is far from useless as a general concept.

    1. this reminds me of a story – I was in the garage of a house a friend had just bought, and we were looking at the furnace. There was an unmarked button, so he bent down, looked closely at it and then pushed it. A flame shot straight out and singed his eyebrows off. I couldn’t stop laughing but seriously, some manufacturer actually put a button on a furnace that shoots flame.

    2. Ooo, I was working on the ignition system for a natural gas fired heat treat oven. Unknown to me there was a small crack in the diaphragm of the main valve and was slowly filling the furnace with gas. I had the door open and I hit the ignitor which should have just started the pilot, instead I got a fireball that rolled out of the oven roasting my eyebrows and bangs. Good thing I wear glasses….

    3. Kids do some really really dumb shit… myself included.

      I wanted to arc weld a couple of steel panels together so had the bright idea of cutting an end off of a power cord and attaching one end to one panel and using the bare wire of the other end to try and spot weld.

      Thankfully my hands were busy as my left hand held the open end (insulated for my self using just the wire coating) and plugging the other end into the 120v AC with my right hand. I haden’t learned the “one hand in pocket” rule yet. I touched the bare wire to the panel and it made such a fantastically loud pop and flash that I dropped the wire and fell backwards in my chair. The wire dance for a bit, skittering across the plate before landing on the carpet.

      I unplugged the mess and got rid of everything before my parents got home.

      If Guardian Angels exist, the hair on mine turned white before I turned 15. I know both my parents certainly did.

  3. Far as I remember from school, this is a competition reaction. So the further apart the metals are on the reactivity series (Please Send Charlie’s Monkeys etc) the more violent the reaction. Copper is near the bottom of the series. So copper oxide + something more reactive should be pretty violent. Iron and aluminium are nearly next to each other, just zinc in between them.

    1. Enthalpy of formation (ΔfH) is more informative. The more negative the enthalpy of a substance, the more heat is released per mole when the substance is produced from the elements (ΔfH for any element is, by definition, zero). E.g., ΔfH for Al2O3 is −1669.8 kJ/mol, whereas ΔfH for Na2O is just −414.2, despite the fact that sodium is more reactive than aluminium. You can calculate the heat released during a reaction (ΔH) by subtracting the total enthalpy of formation of its reagents from the total enthalpy of formation of the products.

  4. This actually has a very valid use. There is a 100 year old company: ERICO – Electric Railway Improvement Company and they make a product called CadWeld. It uses copper thermite to fuse radio ground rods to the copper ground cable.

    DX Engineering sells it – pretty cheap, about $8 per shot. Comes with a crucible to go over the ground rod and slots for the wires coming in. Your end result is a blob of metallic copper and a bulletproof connection.

  5. Quicklime, CaO is probably a metal oxide which is the most obtainable from nature in quantity, through low/traditional tech. Now, what pure metal filings would had ancients had at their disposal, for fuel part of the mixture? Meteorite iron dust?
    Or, perhaps they could had pulverized some corundum (Al2O3) rocks instead of baking the limestone, and then get thermite proper. From that, they could had made molten iron for casting.

    1. I don’t think you quite get it. You want the oxide of a low reactivity metal, such as iron, and an unoxidized high reactivity metal such as aluminum. In the reaction, the oxygen changes places, so you’re left with pure low reactivity metal, and oxidized high reactivity metal, so Fe + CaO is the products of a thermite reaction, not the starting mixture.

      CaO will only give you a thermite reaction with very few metals. Potassium, sodium and lithium are the only reasonably common ones, and these are all hard to purify (logically enough). Alumina will also react with magnesium and calcium, but still nothing the ancients could refine.

      Really, that’s looking at it the wrong way round — the question isn’t what oxides they could use, but what’s the most reactive metal they could purify? The most reactive element extractable before electrolysis was zinc, and while this was somewhat known to the ancients, it was principally used in alloys, especially brass, and as far as we know, not intentionally refined as a pure metal before perhaps 1000 A.D. (we have references in India from c.1300, IIRC). Second best was iron, and that is our most likely candidate — whether meteoric or, eventually, refined from ore.

      Then we need a compatible oxide — anything less reactive than iron will do, the lower the better (both for speed of reaction and ease of ignition). The noble metals (silver, gold, and platinum) are of course best, but both rare and relatively hard to oxidize. Silver is the best on both counts; it’s not inconceivable to produce either oxide of silver, and use it with powdered wrought-iron as a thermite, but I think copper is a much better bet.

      As for the actual performance and ease or difficulty of igition, I really have no idea — you should talk to someone who actually knows chemistry, not just how to look at a table of reactivity. I suspect it will be very disappointing, but I really don’t know.

  6. Extreme caution is advised with copper(II) oxide thermite. The combination is used in high-power rocketry as an instant-on motor starter for solid propellants. The general instruction is to make the mixture only when it’s about to be used, and to confine it oh-so-little; with a cigarette paper or a single wrap of HandiWrap. More confinement than that and the mixture literally explodes, showering the unlucky individual with molten copper. It’s friction-sensitive to boot. I have a good friend who had to have skin transplants as a result of such a device (about a gram of mixture) when it went off as a result of friction..

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