Picture of microwave smelter

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:
Want to see how it's not done? Let's go!
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Step 1: Tools + materials

Picture of tools + materials

  • oven mitts
  • safety goggles + face shield
  • metal tongs / grips
  • old microwave
  • stainless steel measuring cup (crucible)
  • silicon-carbide block (details in step 2)
  • ceramic casserole dish / fire bricks
  • tin / lead / silver solder (details in step 2)
  • mold for metal ingots (pancake mold)

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jscanlan7 days ago

Interesting experiment. I agree with Void Schism comments, I was wondering if it was going to get more exciting with the water put on the electronics. There are some low temp casting alloys out there that may be interesting to try out.

bonpierce3 years ago
You do realize this contains LEAD right? Lead is a carcinogen whether it is being melted or held in your hand a a charm or around your neck as a necklace.

You don't want long exposure of any kind to this stuff. Seriously.
Lead isn't a carcinogen. It's a toxic, heavy metal - a poison. That's different. It isn't going to hurt you unless you ingest it, either by eating it, chronically getting lead paint (which isn't sold anymore) on your skin or by inhaling the fumes after it reaches it's vaporization point which is a whole lot higher than it's relatively low melting point. If one were to smelt lead every day, there would be danger. One time isn't dangerous if you are the least bit careful.
jeffm7 terpodion2 months ago

It can also be absorbed through the skin in solution.

Do you remember good old time of tetraethil lead in gasoline ? I guess some of that stuff is stil spread all around
So why is there this huge push away from it for consumer (and most other) electronics?
Because it if it ends up in landfills it contaminates the water table. Of course, every public waste disposal site that I know of keeps electronic junk out of the landfill and recycles it properly but because it once did end up there; politicians created the legislation to eliminate lead in all forms. Makes for good campaign bragging rights. "Senator Jones drafted legislation to eliminate lead and protect our children."
Then why do we still use Lead Acid Batts for vehicles?
Because there is no acceptable substitute. It's pretty much as simple as that. No other type of battery can stand up to the thousands of cycles of charge / discharge, put out as much current and withstand the environmental conditions that vehicles are subject to. At least not in that price range. How would you like to have to pay $350 to $700 for a car battery (installation not included)?
skaar terpodion3 years ago
i've read that iron acid batteries are better for lifespan and resiliency, but they're low capacity. now ni-mh could be used, they have low size, high current and capacity. at least acid iron could be built at home.
Lead Acid batteries are still being use for vehicles because an all around substitute hasn't been created. The hazards of using them have been mitigated to a large degree on both the manufacture, and consumer end. The salvage price for lead has always been constantly high enough that persons in the know, never sent them to the land fill. The high deposits we see now on new batteries is to keep the ignorant, and lazy from sending them to the landfill.
Also, due to the large deposits encouraging battery exchanges, something like 98% of car batteries are recycled.
I think too there is a certain paranoia about lead. This paranoia is, in part, spread by certain legislators who, in an effort to look as though they are actually earning their salaries, play up the supposed dangers of "demon Lead" and pass legislation against it. If the web site I looked at earlier is correct, easy flow silver solder contains cadmium which is definitely something you don't want to breathe the fumes. I have read cases of jewelers killed by melting cadmium and breathing the fumes. I have yet to see anything about anyone dying from melting lead. If melting lead was that dangerous plumbers should have been dropping like flies before legislation banned it in plumbers solder. I believe the effects lead has on the brain and nervous systems of immature humans is the main thing we must be careful of when dealing with lead and that is more likely to incur through ingestion.
This is a good point. It's easy enough to find "Lead Free" solder these days (Sn-Ag-Cu), people should just use that if they plan on handling their ingots (as a paperweight, etc) created here.
You realize however that lead-free solder is actually worse for you.
*citation needed.
I had originally heard about a Danish study through a television program, so I had to do some quick research to get you facts you can read yourself.

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...
Wow thats really quite the paper I said to myself I'm just going to skim it than I got to the end and was like wow that was informative. I reccomend that to anyone who wants the real scientific answer to whether or not LeadFree Solder is More harmful to you. Which apparently it is.

Que instructable about making an effective deskmounted airfilter for your soldering station.
I'm glad you found it informative. Too often people just assume that lead-free means safe and they use it without proper ventilation, doing god only knows what to their lungs...

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.
Well thats handy, I dont exactly work in a production environment where I'm soldering ALL day. But this is good to know I also was under the same assumption.

I've been using this stuff the "Special Blend" at Sparkfun, 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.
If you read the MSDS, it has basically the same ingredients and warnings as other non-lead solders. What I would be concerned about is two statements;
  1. Prolonged inhalation of fume may result in lung complications.
  2. This product may contain lead. (So much for being lead-free...)
It's important to read it if you haven't already. :)
Actually the MSDS is not a datasheet for the Sparkofun product. The data sheet is for Indium solder products that Sparkofun lazily points customers to. Early on the data sheet states the warnings concerning lead apply to those Indium products containing lead. The datasheet is usable, but you need to know what it is you are looking at, and how to apply it to the Sparkofun solder product. A thousand lashes of Ann Landers wet noodle for Sparkofun, for confusing people about their products.
While I find the linked PDF interesting, I can't give it much credibility because of their inability to correctly quote the name of the largest occupational safety organization in the US. It seems like a miniscule detail, but they're making a lot of claims, and citing a lot of other works, not to have done their research, or at least proofread the work before publishing.
Yes, I see too that they referenced OSHA incorrectly as OHSA.
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.
Certainly is. Always read the material Data Staftey Sheets about any of these things.
Lead free solder was used in a lot of volkswagons, xbox, and pretty much everything else where the environmentalist went on a rampage to get rid of lead. that is why you get the red ring of death in an xbox and your airconditioner in your volks wagon. Especially in deisel. Environmentalist did not think ahead about all the crap going into a landfill because it can't stand up to any heat and or vibration.
Would appear that not all lead free sold alloys are created equal. Who knows exactly why they weren't properly researched by manufacturers, or those specifying manufacturing specifications prior to their use? This is not the first time a change(for any reason) in manufacturing methods created problems, and it will not the last. Of course it's all the fault of the environmentalists.
hiya folks Safety is a myth, risk is the reality. Paracelsius said " The poison is the dose" in the 15th century. As abinger says below, risk/dose increases with, time exposed and the ability of the product to get into your body due to its form (gas, fume, mist, powder, pearls, bricks...its pretty hard to inhale a brick). Spoken by someone with 16 nuggets of mercury amalgum in his gob(mouth) I feel Ok about it. Loook at it this way Acetic acid /vinegar pretty much the same chemical different concentration use one in the lab and a lower concentration use it on your chips(french fries) drinking it ...but don't want it in my eye. Same chemical same strength different risk. Phosphoric acid used as a disenfectant sanitiser in breweries, used as a main ingredient of Coke...okay bad example. As a safety professional( and ex lab tech with 30 years behind the bench) I genuinely appreciate people's need to communicate safety ideas and protect their web community friends. High five hazard spotters! But educate yourselves to the risks not just the hazards. Google EH40 and you will find the UK occupational exposure standards for all controlled chemicals and peruse the Health and safety executives website at all info free and usually pretty practical. I would love to write a safety bible for this site but where would you start and end..ohh yes Asbestos to Zoonoses (an A to Z of not so common sense) Bout ye.
soundmotor2 years ago
mikeasaurus: although they did not cause any problems for you, you might want to try firebrick next time. Firebrick is not porous like red brick so it does not retain moisture. If your red brick is stored outside they may. Mosture in red brick + heat could = steam with a resulting.....KABOOM!
jeffm7 soundmotor2 months ago

Looks like he was cutting Styrofoam and not some kind of refractory. Use Kaowool ceramic blanket next time or insulating firebrick. Insulating firebrick is softer and easier to cut and shape.

dlivings3 years ago
Funny to read all the scaredy cat comments. People are so misled. Actually water is not very conductive nor dangerous as folks think around water. When you add soap / or salt to it , it becomes conductive. I saw mythbuster stooges tell everyone that a toaster in a bathtub is lethal. I will jump into a bathtub with a toaster and smile all the while and jump out unphased, (because I know not to touch any metal with my hands) It takes 2 poles to be shocked.. When people die, is when they have their fingers wrapped around a metal conductor. The electricity contracts your muscles and makes it impossible to let go. If electricity has caused your house to catch fire, you'd better get some water on it! If you're scared, then put on a dress. Also, you can never put FOIL into a microwave. nor the plates with gold painted fancywork. As a rule of thumb, you should not put silverware in the micro unless there is 1& 2/3 more mass of water. And never with the silverware against the side of it, because it can create a pocket that traps microwaves and will spark which burns holes in the paint.
jeffm7 dlivings2 months ago

Most municipalities add chlorine and fluoride and several other salts to public drinking water. Even well water has dissolved salts in it. I doubt anyone keeps a bucket of de-ionized water just sitting around. If I were a betting man, I would bet the water came from the city water supply which is very conductive. Scared of dying is what I am. Never pour water on an electrical fire unless you want to commit suicide.

finton dlivings2 years ago
Tee hee. "I will jump into a bathtub with a toaster ... and jump out unphased". You mean "unfazed", but "unphased" is an apt misspelling when talking about electricity!     :]
irongus1 year ago
this is not smelting. its just melting metal and u do not need the silicon carbide susceptors to create the heat. arcing in the solder material would provide heat. smelting as far as I understand it is the reduction of ore...iron oxide or other ore bearing material into metal. its a chemical process. heating up ore will not reduce it to metal. I have safely melted steel in my microwave without external suceptors to create the heat and there are some good patents in the uspto that describe microwave remelting techniques it is a a good first try.
ehhdean1 year ago
Any idea what temperature it gets up to? I'm looking at melting down some bismuth.
well silver melts around 1,762 F. and bismuth around 520. i think you'll be good. ;D
kelseymh1 year ago
You do not want to use water to douse the sort of fire you caused in your microwave!
Instead of the bucket of water, keep a bucket of dry sand on hand. A small 1-gallon bucket like you have will have enough sand to fill the microwave, and will be light enough (about two to three times as heavy as the water) to pick up and throw.

You don't want to have to remember to unplug the burning oven before using the water -- stop the flames FIRST! When you forget, you'll have bigger problems on your hands. Also, throwing water on molten metal is going to generate superheated steam and droplets of boiling water coming back into your face.

Once you have the flames suppressed, you can unplug the unit, or throw the breaker, or whatever you need to do to finish cleaning up the mess.
mikeasaurus (author)  kelseymh1 year ago
Good safety tips.
The video doesn't show the full dangerous hilarity of the unprepared attempt: The microwave was unplugged after the insulation caught fire and there was a good moment of panic when we couldn't decide to close the door to starve the fire, or open it to extinguish. We left it closed, and the fire started melting the microwave, opening the door made it worse and the fire extinguisher had no pressure (dial indicated it was full). The water was only meant to be used as a last resort, which quickly became our only resort. I had my doubts that the microwave would get hot enough to work, and didn't prepare adequately.

I think I covered safety well enough in written form, but people draw all kinds of conclusions from watching the video without reading the narrative.
Never forget the last words of many a Darwin Award winner, "Hey, guys! Watch this!"

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