Remember how your parents used to say "don't put metal in the microwave"? Prepare to throw that cardinal nugget of advice straight out the window because we're going to do just that. We're going to use a domestic, unmodified microwave to melt metal!
I happened upon an article in an old Popular Science magazine (c.2003) about microwave smelting and thought it was so awesome I had to try it for myself. So, just what happens when you try to smelt metal in the microwave? Turns out, it works!
Also, if you do it wrong you end up with a fiery microwave disaster:
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silicon is another cancer causing agent..
I think the cause of confusion on this issue for most might actually be a spelling mistake. *Silicone* (notice the 'e') is in fact a proven carcinogenic compound of several polymeric and plasticine components. *Silicon*, in compound with additives such as carbidinium, may in fact be carcinogenic (I personally don't know for certain), but by itself, its practically an elemental substance and is at least 98% inert. It doesn't break down into other components. If you melt it down (extremely unlikely in ones backyard microwave) it stays the same substance, just in a liqiuid state. It is, in fact, a major component of such naturally-occurring things as basaltic magma and lava, (and of course basalt itself), and is also present in almost every crustral formation on earth. The last I heard, basalt doesn't cause cancer. I may, however, be proven wrong on this. Only time will tell.
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The hazard comes from the diameter of quarttz particles, the smaller the inner you'll get them into your lungswhen breathing and more or less you'll never get rid of them. The quartz particles ,like asbestos fibers , are almost totally inert and the problem comes from your immune system effort in getting rid of them. So best thing to do is is keeping away from any kind of mineral dust, hard wood saw dust, carbon fiberst, concrete dust and whatever . Avoid dry hammering of rocks . Wear an appropriate mask.
An intersting source of ultrafine dusts are steel wheels of trams smashing anything happens to lay on rails in dry weather period and the concentration of those dusts in an important crossing in a heavy traffic hour? You can easily see what happens and on check on sight powders concentration pointing a green laser in the suspected area , the greener the worst . See also the mazing difference brtwuen a dry and a rainy day , I shall say I am amazed from this kind of quick air checkings.
"if you go to Salvation Army or Goodwill, I have seen several old microwaves for like 10 - 20 bucks! so much better than risking your own! :\"
I read this in my email and am confused beyond belief, but i learned something non-theless :P
NEVER pour toward yourself & Please wear safety faceshield & glove!
Somehow make a handle or tongs to allow you to pour to the side!
There is a VERY REAL POSSIBILITY of SPLATTER when the molten metal strikes the mold.
*Extremely Important*: If there is a HINT of MOISTURE on the mold this is not simply a possibility, it will be a reality.
PLEASE, be super careful about this, molten metal burns are not funny!
BTW, I'm an assayer for a refinery - I've had pours splatter & I've seen others have this happen to them!
One thing (out of all that could be added about safety) that I would like to add, if I may, is ALWAYS HAVE SOMEPLACE NEARBY TO SET YOUR CRUCIBLE.
Worst than having an accident is dropping your crucible and creating bigger splashes. Bear the pain for a split second and put the crucible down. This is why it is important to have someplace in the immediate area.
I prefer a couple bricks (fire), and having a bucket of sand can also be helpful to allow any unused or remaining molten material to flow to a clump in the edge by sitting your crucible at an angle to cool.
I love this idea... it's freaking crazy, but considering using a propane forge, I guess this isn't so bad. At least it won't blow up, and you can just throw a switch to stop the process at any time. I'd like to see someone "in the know" with this process do a Pewter casting before I attempt one, though.
What makes this so important is that it's one of those 'at the last minute' things you don't realize until you're already there and it's effectively too late.
I'd be more concerned about breathing that.
Have any of you ever read
http://www.gizmology.net/stovetop.htm
there is a fantastic article about smelting Zamak. Its Zinc, because of its low melting point, with Aluminium (and a touch of copper) dissolved in it.
Makes for a very useful alloy for casting, but can be made at relatively low temperatures.
The next candidate for microwave smelting?
You don't want long exposure of any kind to this stuff. Seriously.
Heres a pdf from a company called OK International, who is a global supplier of soldering products. In it they reference the study and explain the results. Obviously being a supplier, they have no reason to manipulate the results either way...
I only chose this source because (someone here wanted me to back up my statement and) Ok Int. references the Danish Study that I had heard about from a TV program.
If anyone wants to read the full Danish Study for themselves they can read it here.
Que instructable about making an effective deskmounted airfilter for your soldering station.
In fact, an Instructable member has already made an inexpensive air filtration system that was intended for use with soldering.
You can see it here.
I've been using this stuff the "Special Blend" at Sparkfun, http://www.sparkfun.com/products/10243 enjoying it quite a bit I will definitely look at that Ible though I do really appreciate my lungs. :)
The area I work in is a pretty open area but its probably still insufficient.
- Prolonged inhalation of fume may result in lung complications.
- This product may contain lead. (So much for being lead-free...)
It's important to read it if you haven't already. :)You're not smelting, you're melting and casting. Smelting is the removal of metal from ore.
Otherwise, carry on. Consider better safety gear.
I have a convection microwave which can have metal pans in it, and the carousel is made of metal. Indeed, the inside of the oven is made of metal, so the issue is not just having it in there. It depends on the shapes and sizes of the metal items, and how they might be connected together.
Put a ring of frozen peas on a plate so they are touching and see what happens. You are likely to get arcing on them too. They are not metal but are conductive, and making a ring forms an antenna loop.
I will have to try this to get better cell phone reception while out in the back woods snowmobiling...beats writting your name in the snow. :-) :-)
Great job for having the cahonies to try something 'out of the box' (or microwave as it may be)
As to the insulation I would suggest trying to score some refractory bricks, they can be had at ceramics suppliers, and cut easily. You may have some luck chatting them up, and getting some fractured or broken ones to cut up.
I'm not a fan of using solder, as much of it can contain fluxes, and it can be pricey. Old (lead) tire weights can be used. Silver might be another possibility, but also can be pricey.
Before we have ANOTHER tirade about how bad lead is, please keep in mind that lead has been used for casting for thousands of years, and while it is very toxic when ingested, or inhaled, simple safety precautions will protect a casual hobbyist.
Remember it is YOU who is responsible for you safety, not someone who is trying (at his own risk) to create something new!
If you're soldering or melting lead-containing alloys, please remember to get your blood tested at least once or twice a year.
While it may be beyond the oven's internals, if one could adjust the frequency, you might be able to reach higher temps.
The other way of loading a microwave cavity is by bulk resistivity. When you put a conductor in the field, it runs current from one end to the other and short circuits the field. When you put a semi-conductor in the field, it conducts a lot but has some resistance across it. If you know your Ohm's Law, you know that there's a point where you maximize the power transfer to a load from a generator. If the resistance is too low (good conductor), your power is shorted out and your load doesn't get hot. If it's too high (an insulator), it doesn't get hot because no current flows.
The silicon carbide has about the right amount of resistance to heat up. Unlike the polar resonance effect in water, this effect occurs at any frequency, including DC. So you can measure the resistance of the material with an ohmmeter. The resistivity changes with impurities, but it's in the 100 ohm-cm range, and is used for high-power resistors.
This 'ible immediately put me in mind of something I saw on TV this year - I think it was Bang Goes The Science - in which Richard Hammond (again, I'm not sure) melted a glass bottle in a completely un-modified microwave. He softend a bit of it first with a blowlamp to give the microwaves some liquid molecules to bang together, and that was able to heat up enough to melt the solid glass it was attached to, and pretty soon there was a heap of mostly molten glass where the bottle had been.
I'm wondering if metal could be started off in the same way, thereby eliminating the silicon carbide - so long as you could prevent arcing of course. Be good to be able to smelt scrap aluminium this way to make pulleys and stuff.
Also put me in mind of this 'ible: http://www.instructables.com/id/Fun-with-Bismuth/ for something to melt other than solder.
Having said that, I have removed all my posts because after rereading them, they sounded(to me anyway) anything but respectful.
I apologize to anyone whom I have offended or made to feel less than the person they are. That is not me, That is not how I do things, that is not my way.
I do not agree with this instructable, and that is all I will ever say on this matter.
My apologies to all.
The risk to life and/or limb is too great.
They need to pull this instructable.
Take this quote and reapply it to Instructables. I think you will see why a site cannot pull this instuctable. As soon as it is pulled then nothing can stop people from pulling any instructable that may be deemed to dangerous of has the potential of being used for illegal ends. Next thing you know the site is empty and user-less and the DIY community is devastated.
My apologies.
I apologize for being so uptight. I will just sit in the shadows & be quiet.
This instructable looks fun and interesting and anyone should use caution when trying to cook or melt anything. I thought we were all grown ups and knew that already. There's no logic behind removing legitimate and useful knowledge.
So I give Two Thumbs Up for this instructible.
keep on i'bling
Check out www.backyardmetalcaster.com and www.metalcastingzone.com for lots of stuff on casting.
There is nothing wrong with this instructable at all, and no reasonable person expects a safety manual to be presented with every instructable. I find amusement in the way the 'room' fills up with safety experts, decrying the project and wishing the information to be supressed, every time someone does an industrial experiment.
Instead of either complaining about the article or having several users post a nearly identical warning, those overly concerned with others' safety ought to collaborate on a document containing the warnings about all kinds of processes and materials and make it available on this site. A hobbyists's safety manual.
It is easy to complain or condemn but it is worthwhile to contribute. Information supression is much more dangerous than home made industrial process experiments . Be safe! - Don't Supress Information!
(So we should all have cancer!)
Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)." Silicon has been shown in university and field studies to improve plant cell wall strength and structural integrity, improve drought and frost resistance, decrease lodging potential and boost the plant's natural pest and disease fighting systems. Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.
To wit:
Silicon as an element will rapidly passivate and form glass (SiO2) on the outside, Quartz if it is crystalline. Silicone is a polymer chain based off of silicon and oxygen, as well, but in -mer chain form and comes in an infinite number of combinations, as you well know, from medical grade to food grade to construction grade. Do you use powdered drinks? Invariably, one of the final ingredients will be "silica", which is nothing more than ground up glass (or highly refined and pure sand, however you want to put it).
I used to handle pure silicon wafers in a chip fab. The only reason to wear gloves is to protect the silicon from you, not the other way around.
To sum up, silicon is all around us. If silicon by itself caused cancer, no one would be left alive to tell the tale. That said, silicate fibers in the form of asbestos can cause mesothelioma, but implicating silicon is no more favorable than implicating oxygen.
I'm very sorry for your condition and wish you the best in your recovery, but also hope that you can help the public good by spreading and clearing up facts and not the alternative.
I appreciated that the magnetron does not directly generate heat. That was one of my problems with melting metal in the past: finding a hot enough heat source that was controllable and wouldn't sacrifice itself in the process. Assuming all the microwave energy gets absorbed by the silicon carbide, it shouldn't be hard to calculate its temperature rise given the mass of the block and the amount of energy delivered by the microwave. Plus, like solar intensifiers, the temperature seems to be nearly limitless (unlike a torch whose flame temperature is the upper limit, the sun has a very high temperature limit, and microwave excitation probably has one, but it's way out there.)
Very cool indeed!
There are children around the world without access to Orville Redenbacher's finest buttery microwave snack, and you go and waste a perfectly good popcorn-creating device. Not to mention baked potatoes and pizza.
You must be the 1%.
Play safe, I hate scraping up friends
Now I am sure this post will receive a lot of flack and that is OK, everyone is entitled to their own opinion. Mine is "Take a chance, it can only be your last!"
er... i mean... OUR SCIENCE!!!
I dunno, I think it would be much more effective to use magnesium instead of the bricks, and some thermite to get everything up to the appropriate temperature...
And while I think that would be a very interesting experiment it's also very likely to create a fire that will probably kill you. 'specially if you throw water on it.
Anyway, I think this is a great project, and if there was some way to do this repeatably and safely with a cheap-o microwave I would totally sacrifice my old microwave to science.
If you want to stick with solder casting, I recommend just picking up a cheap-o solder pot for around 40 bucks. Does the same thing, without the flames. Of course it's not nearly as cool.
I would like to see you do bronze next. Either making it as an alloy of copper and tin, or just finding a chunk of bronze and making it into something cooler. There is no better way to learn science than by doing it, and I applaud you
So which metal worked better? It looks like you're holding two in your hand at the end - one that made a crisp, defined ingot, and one that's a little more... "organic" in shape?
Thanks for documenting and sharing.
If all the cave men sat around a pile of wood discussing what the discovery of fire could cause, for example forest fires, house fires or cave fires we would never have been able to have weenie cook outs because of weenie heads worrying about every thing that could happen. Fire would not have been discovered or used and all the cave men would be sitting around a wood pile eating raw pork, beef, and mechanically separated chicken and turkey! Yummy!
This is a dangerous entertainment, like sky diving. There is a very tiny chance it could kill you. If you want to get your kicks that way, fine, but don't confuse it with science.
As Miss Frizzle used to say, "Take chances, make mistakes, get messy!" How on earth are you ever going to learn anything if you don't!!
"The only perfect sight is hind sight" and the only way to get that is to do!
My cousin used to smelt old car pistons with a pottery kiln and made this mistake. Once.
I'm just thankful that all the great inventions came about before Health and Safety stuck their ill-informed and generally miserable nose in...otherwise we'd have none of the beautiful machinery and artifacts with which we are now surrounded.
Great Instructable!
Mostly to the "Add a danger scale" than the rest, but it's definietly a GOOD IDEA
The point being, the microwaves will heat anything as long as it is liquid (ie, has molecules that can be jigged around), and heated up the softened glass enough to melt it, then the bit it was joined on to, and so on.
It would be really good if this method can be used with other metals, like bismuth (see this 'ible: http://www.instructables.com/id/Fun-with-Bismuth/ ) or to make something really useful, like aluminium pulleys and things. (Unfortunately I don't think I'd be allowed to...)
Stick to stainless steel or ceramic crucibles for anything more intense than Bunsen burners or conventional ovens.
Add a colon to your link in your "start" link for melting points of metals.
Again I like this. It has me thinking about another project I have been thinking about for a couple of years. I'll give you a clue though. Your water bucket would be turned into an oil bucket, although water will work fine also.
I'm sure there's a disclaimer that absolves the site of responsibility for accidents somewhere, but I'd get someone on staff with a background in industrial safety. Having an instructables staffer cook this up doesn't help the site image.
What are the white bricks in the picture? Are these the slabs of insulation that you are telling us NOT to use? There seems to be a disconnect between the written and the visual instructions that is a bit alarming! I sure wouldn't want to make a mistake with an instructable like this. Could you clarify?
The instructions are clear and I quote "DO NOT DO THIS!"
Very cool idea. Nice to see it done considering I don't think I have the nerve to try it myself. :D
Using a micro wave to slump or fuse glass, however, is a project that is quicker & easier then using a torch, but I would recommend obtaining the commercially made kiln for that purpose because they aren't that expensive.
In casting, you always need some superheat - the melt temperature above the melting point or in the case of an alloy the liquidus temperature. Plumbing solder is NOT a eutetctic solder like electronic solder is purposely so crystals will form in the liquid and the liquid will still be well above melting temperature. This allows it to form joints in wider gaps than would be possible otherwise - if it was all liquid it would run out.
Preheating the mold simply makes the initial bits of liquid that go in cool slower so you don't get solid blebs from that preventing new liquid from flowing in and filling the voids.
So solutions are to heat the mold, heat the melt hotter, or use a melt composition closer to the eutectic.
DO NOT USE WATER ON ELECTRICAL OR METAL FIRES!!!
Clearly the power was disconnected and the metal had been removed, right? (nod convincingly)
wetting electrical fires can result in electrocution and pouring water onto molten metal can cause steam burns, expolsive thermal stresses and molten metal spray.
Get a CO2 extinguisher and keep it to hand. A bucket of sand is also a good idea for those "why is it still burning... oh #@%& itsathermitreaction!!!" moments
Have fun, be safe and if it blows up post photos ;)
To be clear, this wasn't an 'electrical fire'. It was an organic fire in an electrical appliance. The process of unplugging the microwave was edited out of the video for brevity. Also not shown was the comedy of panic than overcame me when I realized that our fire extinguisher was not operating and we had to jump to our backup plan of water.
For the kids in the back row not paying attention, I've added another disclaimer to address your comment in step 3. Thanks for the prompt!
Always put the metal in the water. Never pour the water on the metal.
If there is a fire, use a CO2 fire extinguisher. The CO2 will displace the oxygen as well as provide rapid cooling.
It's also advisable to avoid wearing clothing made from synthetic materials, especially your shoes, when preforming this kind of task. Nearly all synthetics will melt and stick to your skin causing severe burns. Cotton and leather clothing offer your best protection when working with molten metal. Heavy welding gloves, instead of oven mitts, are also highly recommended.
The transformer inside, combined with a HV capacitor and diode can reach up to 4,000 volts of AC electricity. And you don't want water near that ;)
But if you do use proper insulation, shouldn't the insulation go around the brick instead of inside the brick?
So, let me get this straight: the silicone carbide absorbs the microwave energy, and gets hot. That's what prevents arcing to the crucible or solder?
I noticed the pitting in the ingot you made, it reminded me of the troubles I had with my custom lego stamps. I also used plumbing solder (though I used a torch to melt it!), and I ended up with pitting and irregularities. Do you have any idea what causes that?
Anyway, great instructable! I've actually got an old microwave in the shop right now and my first thought was "Oooooooooh . . . melting stuff!", but I think this time I'm going to restrain myself.
I cast a few ingots and had pitted results each time, I think it's caused from the temperature difference between the molten metal and the cold mold. We tried to warm it up prior to casting, but with limited success. Maybe if we had more/better equipment we would preheat the mold. A preheated mold and some gentle vibration I think would allow any gasses to escape and create a smooth ingot.
You should definitely try it, Ian! It's just the right amount of danger and impracticability to make it worth a weekend project. You know I want to see your results!
http://www.metalwebnews.com/howto/cuttlebone/cuttlebone.html
and
http://www.pennabilli.org/tecniche/CUTTLEBONE.htm
If you were casting pistons for engines I'd say it wouldn't work but since your casting was relatively flat and not all that large then by all means give it a try-
Bonus! they aren't expensive and if you're careful can be reused!
I've still got the negative from that experiment so I may try again some day. Perhaps I'll attach a small pager motor to the edge, to vibrate out any gas bubbles?
I did a similar experiment a few years ago, and with a few changes you can be melting IRON in your microwave.
First - use firebrick or rock wool for your insulation, which can easily withstand the several thousand degrees that may be generated. It's also cheap.
Second - get a proper ceramic crucible (or maybe just a ceramic mug...?) also to withstand the heat.
Third - get your hands on a healthy amount of black iron oxide (also known as Fe3O4 or hematite... magnetite sand might also work). I bought a 10lb bag for dirt cheap from a pottery supplier... you can get a 5lb bag from amazon for $20 right here:
http://www.amazon.com/Black-Iron-Oxide-Natural-Pounds/dp/B004KICAVU
The structure of Fe3O4 makes it readily absorb microwaves. The only catch is that it has to be up to a certain temperature (somewhere around 600-800° F I recall) before it starts to heat up aggressively, so using another material as a "starter" will speed things up (with enough time in the microwave, it will melt on its own, but it will happen in less than a minute if you get it up to temperature)
The Silicon Carbide used in this instructable would probably work as a starter... I experimented with using graphite with moderate success.
Once up to temperature, the iron melts rapidly, and somewhat violently. I'm sure there are ways to control this, as well as draw out the some of the oxygen from the mixture to give a purer end result. I wasn't able to test these, as by the time I had figured out how to reliably melt it at all, I burnt out my microwave.
Very Nice.
I wonder if the surface finnish of the ingot could be improved if solder flux was smeared on the bottom of the mold like you would put grease on a cookie tray?
Fun discussion! Howard
You could also use bismuth to make custom molds...why get that messy?
In the worst case scenario i'll end up with stuff to make an arc welder :-) (which i wanted to use it for in the first place) :-D
Sunshiine
I melt metal the old fashioned way over flames.
Good Job! I will try this one day! Very cool, thanks for sharing.
I hope that the MWO has been saved from destruction. Here in the third world can not all afford to have even an old MWO.
I didn't know her well, but will always remember the time we smelted metal together and how she held back the licks of fire for a few solid minutes while I got my camera ready.
Wouldn't you want a shallower metal crucible since it shields the microwaves or is the idea to heat the crucible which melts the metal inside?