Finely powdered aluminium can make almost anything more pyrotechnically interesting, from fireworks to machine shop cleanups – even ceramics, as [Degree of Freedom] discovered. He was experimenting with mixing aluminium powder with various other substances to see whether they could make a thermite-like combination, and found that he could shape a paste of aluminium powder and clay into a form, dry it, and ignite it. After burning, it left behind a hard ceramic material.
[Degree of Freedom] was naturally interested in the possibilities of self-firing clay, so he ran a series of experiments to optimize the composition, and found that a mixture of three parts of aluminium to five parts clay by volume worked best. However, he noticed that bubbles of hydrogen were forming under the surface of the clay, which could cause cracks during the firing. The aluminium was reacting with water to form the bubbles, somewhat like a unwanted form of aerated concrete, and for some reason the kaolinite in clay seemed to accelerate the reaction. Trying to passivate the aluminium by heating it in air or water didn’t prevent the reaction, but [Degree of Freedom] did find that clay extracted from the dirt in his back yard didn’t accelerate it as kaolinite did, and the mixture could dry out without forming bubbles.
This mixture wasn’t totally reliable, so to make it a bit more consistent [Degree of Freedom] added some iron oxide to accelerate the burn through an actual thermite reaction – some mixtures burned hot enough to start to melt the clay. After many tests, he found that sixteen parts clay, seven parts aluminium, and five parts iron oxide gave the best results. He fired two cups made of the mixture, a thin rod, and a cube, with mixed results. The clay expanded a bit during firing, which sometimes produced a rough finish, cracking, and fragility, but in some cases it was surprisingly strong.
The actual chemistry at work in the clay-aluminium mixtures is a bit obscure, but not all thermite reactions need to involve iron oxide, so there might have been some thermite component even in the earlier mixtures. If you need heat rather than ceramic, we’ve also seen a moldable thermite paste extruded from a 3D printer.
Thanks to [kooshi] for the tip!
He should try dusting the outside with copper or silver powder before igniting. See what happens.
Since chances are he will not, and I am curious, could you elude to what may happen here?
I dunno, might melt and leave interesting patterns or flecks if the temperature is high enough.
Might require more than a dusting. Maybe thin wire or foil strips pressed into the clay?
Put a tray of water next to the plastic bag, and invert a jar in the water. Run a tube from the ziplock bag to the jar so that the gas from the ziplock bag is captured, and now you have something that can be tested.
Put a smouldering match in the jar, and if it catches fire then the gas is probably oxygen. Put a lit match into the jar, and if it goes out it’s probably CO2. Bubble the gas through lime water, if it turns milky the gas is CO2. If the gas goes pop when a lit match is used, it’s probably Hydrogen. Ammonia and Chlorine can be detected by smell, neither is particularly dangerous in small diluted amounts (open the jar away from your nose and gently waft the contents towards you).
If you know what gas is being generated, it will help you pin down the reaction.
Additionally, I strongly suspect that inconsistencies of burning are due to inconsistencies of mixing. If you had some sort of machine that could mix the clay more thoroughly it would probably lead to better results. A simple meat grinder would probably work – hand mix the powders into the clay, then run everything through the meat grinder 5 or 10 times for good consistency.
‘Hella intreresting video.
ChatGPT does not know of any reaction that might happen between Aluminum powder and clay, so this video might be doing original science. A literature search would confirm this.
ChatGPT does point out that in certain circumstances the environment might catalyze the aluminum with water to release hydrogen, viz:
2Al+3H2O→3H2+Al2O3
So if anyone captures the gas and does the flame test, be a little careful – a pint of hydrogen can pop strongly enough to shatter a glass container.
Who cares what ChatGPT “knows”? Search the literature yourself.
Who cares what the literature says? Do the experiment yourself.
Burn a book and it will keep you warm for 15 minutes. Read a book and you’ll die from hypothermia.
(And if you’re burning bibles or torahs, there’s nothing of value lost anyway.)
Claude says the aluminum is reacting the silica (SiO3) in the clay, and explanation sounds plausible to be. I guess that shows how bad the village idiot ChatGPT is.
Silicon oxides and aluminum are a thermite mixture – which is how the self-firing clay works in the first place – and the water can catalyze the reaction alone or in the presence of other impurities. The reaction would continue until the water is driven off. The gas that develops is mostly going to be steam.
If that is the case, then forming the clay with the aluminium using some other solvent or binder should work better. The solvent cannot be ethanol, methanol, or isopropanol since those would attack the aluminium. Acetone should work and dry up completely.
Another alternative is to use minimal amounts of water to limit the reaction and pressing the damp powder into shape in a form.
That analysis might be possible, but thermite reactions produce solid and liquid products, so any gasses that are produced would probably only be side products. My main guesses were that the aluminium might be reacting with hydroxides and hydrates to release hydrogen, which would be what actually burns in the flame, or that the aluminium might be reducing silicates, as described by
https://thehomescientist.blogspot.com/2010/03/experiment-silicon-dioxide-thermite.html
The one detail that makes me question whether this is actually reducing the silicates is how easily this seemed to light, compared to how hard it is to light silica-aluminium thermite.
I wonder if mixing in a small amount of some kind of oil (either mineral oil or sillicone oil) could act like flux to improve the smoothness of the resulting surface?
That oil would have to burn off, which would likely lead to voids and cracks.
Finally a way to keep my coffee warm.
I learned about thermite while reading about the SAS beginnings in WW2 in Africa Corps airfields, when they helped the germans to keep the aiplanes engines warm during the harsh and cold nights in the desert.
I wonder if Lufthansa – inspired by history – will introduce this cups to serve hot coffee (or sake for flights in Japan).
Africa is very hot. SAS probably destroyed planes used by Germans who were stationed in Norway.
Most of their “legend” though, is mere hype created by modern games, especially Call of Duty. Soviet partisans made far greater contribution towards defeating Germany than brits or frenchmen.
Forget the name of the book, but it tells the SAS story from begining till the end of the war. Starts with major Stirling in crotches bypassing the secretary and going to general Autchinlek (chief of british army in Egypt) to tell the ideea of a comando unit, jumping with parachutes inside the enemy teritory. After a big failure following the upper echalons orders to try a large formation airplane jump (in the middle of the storm 3/4 of soldiers died or got captured), Stirling pushed to smaller groups (5 or 6) being ferried by the LRDG (long range desert group – scouts basically), then sooner including parts of LRDG and especially ther pink painted vehicles (invisible from the air in the desert). After some time they got jeeps from the americans on which they mounted 2 or 3 Lewis machine guns. They raided german airports at night. First they put incendiary-explosive bombs (invented by their major Lewis by mixing thermite with mineral oil) on the planes, then they started riding in two columns shooting at the nice parked planes left and right. At some point Stirling got caught by the germans, tried to evade several times, got caught because of him being 6 feet and more tall, then finally sent to Codlitz. SAS continued without him, going to a catastrophic mission in Crete, but over all proving their motto: who dares wins. At the end of the war their unit was disbanded, but soon after SAS was recreated to become even more faimous and misterious, as we know it today.
The british are crazy and stubborn, but sometimes they are crazy and stubborn in the right way pushing events to the right direction against all odds. Like gunpodwer in a gun barrel.
Chapeau.
Does anyone know the name of the book ?
Please post it.
That book is somewhere in my parents house. Searching the net there is a book by Ben Macintyre called “SAS heros and bastards” or close to that.
Thank you very much!
Don’t be a dumbass. He wasn’t talking about WW2 as a whole, and if you’re going to argue who made the biggest contribution, certain few people was way more important to the big picture in defeating the Axis than all of the Soviet partisans bunched together, and those mainly comes down to technology innovations. Like the quite few persons that figured out the VT fuse (proximity fuse) and the radar, the magnetron and created usable systems from that. Or those that broke Enigma and Lorenz codes.
But far more important is that you seem to have ignored that Soviet and Nazi Germany where working together for the first 2 years, and Soviet invaded Poland, Estonia, Latvia and Lithuania and so on. If it hadn’t been for British resistance and continued war against Germany, and Germany eventually attacking Soviet a couple of years later, those Soviet Partisans would never have existed, or been on the Allied side. Any Soviet partisan action during those years would have rightly been seen as Terrorists attacking innocent people, by the people and land that were invaded.
SAS absolutely was effective in North Africa, and that small group destroyed more planes on the ground than the Airforce did. Two good books are ‘ken Connor – Ghost Force, the secret history of SAS (1998)’ and ‘Steve Crawford – The SAS Encyclopedia (1996)
There was no such thing as “Poland” after sept. 1939. Entire government fled abroad first to Romania and then to UK, abandoning its armed forces and citizens. Without legal government to represent the country, those who kept fighting became unlawful combatants and Germany had every right to exterminate them – this is the Laws of War (same deal as with IGIL in Syria). If president Mostzitzkiy accepted responsibility for nation’s defeat, met with Hitler and signed the instrument of surrender then it’s very likely that all the atrocities of Holocaust would have never happened. Unfortunately polish cowardice prevailed and jews paid the highest price.
In terms of defeating Germany the Brits (and all the Empire nations, displaced Poles, Frenchmen etc that fought with/for them) probably have the greatest claim by quite some margin, having been in the war against Germany from the start rather than their ally as Russia was. And the British developed a rather large array of useful new technologies over the period, along with producing rather large numbers of tanks some models of which were only kept in production because the Russian’s wanted more of them… Not to mention the code breaking efforts that are probably the smallest single element with the largest impact.
Next biggest claim for defeating the Germans to me is probably a toss up between the USA and the informants on the ground in Nazi occupied Europe – USA when they finally get involved directly do very heavily tip the balance through shear numbers and industrial might so the contribution certainly can’t be belittled, but all the men, guns and tanks are next to useless without the intelligence information to use deploy them well. Where with that decent intel even a small force can be very effective, and lots of that comes from the folks stuck under a Nazi or Vichy French (much the same thing) boot and the codebreakers.
Though I’d also have to give special credit to the mostly Norwegian operators on the ground and bombing efforts that kept Germany from getting its heavy water production going, as if they had developed the nuclear weapon first… (Though historian suggest Germany would likely have been beaten in that race anyway)
As for “legend” the SAS have a now rather well documented track record for the period, and while quite possibly exaggerated in some games but with so many of the facts about their history being stranger than fiction ever could be…
I’m pretty sure water is a problem. In ceramics, a clay object is put in a drying room for a couple days to a week? Someone from a Univ. ceramics department will chime in I hope. The the kind of leather clay can be trimmed and adjusted and handles added with slip for glue. Then it can be low fired to bisque, which is porous, and glazed if wanted. Some things are low fired after this with low temperature glazes. The kaolin types are high-fired as high as “cone 10” for vitrification and the high temperature glass effects. I probably have this inaccurate in places. The point is that the drying process is long and multi-stepped.
The burning reaction look at hot as cone-10, almost 2400 deg F / 1300 C. Hot enough that can not see anything inside a kiln because it is close to be a black body radiator and everything inside is emitting the same spectrum. The question is, does it take time to get vitrification?
Vacuum chamber would help? Eventually a bit heated.
Kaolinite clay is might be considered a mix of aluminum oxide, Al2O3, and silica, SiO2 (really, Al2Si2O5(OH)4). The thermite (Goldschmidt) reaction depends on heat released when aluminum powder steals oxygen from something else, yielding aluminum oxide. Obviously, it’s not from the Al2O3, which is already the end product, but the silica (and iron oxide) provide the oxygen.
Perhaps adding more silica to the kaolinite, rather than iron oxide, might produce a more durable product. You might also experiment with other comparatively low-melting oxides, such as Bi2O3, to see if that helps reduce cracking.
Smells like victory!