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Science Technology

A Foundry in Every Kitchen 310

Posted by michael from the we-are-not-responsible-if-you-burn-your-arm-off dept.
WolfWithoutAClause writes "Bored with making the same old food or plasma in your microwave? David Reid sounds like he is. He's using his domestic microwave oven to melt iron, silver and bronze! Over 900C! I don't know about you, but I'm going to be checking the temperature of my pizza rather more carefully in future..."
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A Foundry in Every Kitchen More

A Foundry in Every Kitchen

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  • For more cool Microwave science... (Score:4, Informative)

    by DeafDumbBlind ( 264205 ) on Monday July 01, 2002 @12:16AM (#3798716)
    Try putting in a CD (Yet another use for those AOL 7.0 discs that they keep sending)

    A burned out light-bulb causes some interesting things to happen as well :-)

    • When i used to work as a repair tech for a local clone computer shop, i used to go and grab all the aol disks outta the modem boxes, and nuke em in the back room nuker (5 secs does it nicely), then tack em up on the shop wall. When customers would ask what the hell had happened to the cd's, i said it contained a vicous trojan horse that destroyed your tcp/ip stack (this was back when aol software had a hugely nasty habbit of utterly corrupting your ip stack) and that i was sterilizing the cd so that people didnt accidently destroy their OS. Customers would nod agreeingly afterwards.
      • I wonder what then would happen if you did that to a MS Office 97 CD. I heard there was something that could make one of those unreadible after three installs. I wonder if that CD cyanide pill could be accentuated in a bath of microwave energy.
    • i saw the CD trick done on a televsion programme once. The presenter warned people not to do it at at home because the fumes given off were highly toxic (some compound of cyanide apparently).

  • Make your own jewlery (Score:5, Funny)

    by dgp ( 11045 ) on Monday July 01, 2002 @12:18AM (#3798724) Journal
    This is sweet! I could forge my own One True Ring - Deep inside Mount Panasonic, a master ring was made on High-Power to rule them all!

  • Microwave Pizza?? (Score:4, Insightful)

    by RJ11 ( 17321 ) <serge@guanotronic.com> on Monday July 01, 2002 @12:19AM (#3798729) Homepage
    I don't know about you, but I'm going to be checking the temperature of my pizza rather more carefully in future...

    Who in the world microwaves pizza? It gets very soggy and loses almost any redeeming qualities.

    • Re:Microwave Pizza?? (Score:3, Insightful)

      by buzzbomb ( 46085 )
      Who in the world microwaves pizza? It gets very soggy and loses almost any redeeming qualities.

      A lot of people. And the ones that know how to operate a microwave properly enjoy it more than the twits that don't.
    • Microwave pizza comes with this magic crisping paper that makes the crust go crunchy. Try it, it's great for impatient people. :D

    • Who in the world microwaves pizza? It gets very soggy and loses almost any redeeming qualities.

      I don't know about you, but when I wake up after a hard night of drinking and I can barely see straight... microwaved pizza is heaven on earth. Actually, any food that can be made in less than 3 minutes and doesn't cause too much loud noise is heaven.

      • You uncircumcised heathens! (Score:5, Funny)

        by Kibo ( 256105 ) <naw#gmail DOT com> on Monday July 01, 2002 @03:33AM (#3799298) Homepage
        I've no quarrel with frozen pizza designed to be microwaved. When hunting and gathering one must accept what one finds. But you savages who defile perfectly excellent cold left over pizza have no place in a civilized society. Some social ills make me wonder what horrible childhood pain would cause a person to behave in such a disturbed manner. But those dysfunctional individuals microwaving delectible left over pizza, clearly they must be shot, incinerated, with their ashes encased in glass rods, buried under a mountain or maybe a salt flat, then covered with lye and never spoken of again.

        When people ask "What's this world coming to?" you can be sure that people who microwave perfect precious left over pizza are at fault. Filthy animals!
    • I'd be interested how quickly peoples REAL ovens reach a decent pizza cooking temp!

      My old one hit 220' in about half an hour.
      My NEW one does the same in about TEN mins - and hits 250'!!!!

      I can be eating real pizza from a standing cold start in about 20 minutes!

  • Hmm (Score:2, Insightful)

    by ErikZ ( 55491 )
    "It must be stated that, at the out-set of these experiments, the researcher was completely ignorant of microwave technology."

    Ack, I'm caught between rolling my eyes and saying "Well, a lot of progress is made by people who don't know what they shouldn't be doing."

    What the hell, good luck guys. If you plan on reaching 900 degrees, I strongly suggest tearing apart that microwave and rebuilding it out of stuff that can take the heat.

    • Re:Hmm (Score:3, Informative)

      by klevin ( 11545 )
      Try actually reading the article. One: they've already done it. Two: it's not the entire inside area of the microwave that's reaching those tempuratures, just the area inside several layers of material that convert microwaves to heat, plus the interior surfaces of the microwave have been layered with insulation to protect them.
    • I have just got to imagine that using the microwave in this fashion is going to void the warrenty.

      now on slightly related topic

      When food, (containing water, a very efficient absorber), is placed in a microwave field having a frequency of 2.4 5GHz, virtually all the microwave energy is converted to heat.

      Now this raises all sorts of interesting safety questions about wireless networking, as well as the current generation of wireless telephones I see down at Staples, etc.

      • IDEA (Score:2)

        by Naikrovek ( 667 )
        would someone please make a 1000 watt wireless radio transmitter.... PLEASE!!
  • Now you can steal gold and silver jewelry and smelt it to some other form within minutes of returning to your evil lair. On the legal side of things, perhaps there will be no more waiting a week for the dentist to make a gold crown. Simply make the ceramic mold, insert gold alloy, microware for a few minutes. Viola, instant gold crown.
    • More uses: Drying out silica gel and refreshing zeolites. Says so on the can.

      More fun: Microwave grape racing. Steam builds up inside, and jets out the stem hole and the grapes scoot around inside the microwave. Ocasionally, the stem hole is too small/plugged with seeds/still has a piece of stem inside, in which case they explode on the starting line.

  • Microwaves are potentially dangerous---no shit. (Score:5, Informative)

    by dc.wander ( 415024 ) on Monday July 01, 2002 @12:35AM (#3798801)
    I feel obliged to say something, before some 13 or 14 year-old kills themselves:

    microwaves are high voltage, high current devices. they can kill you EVEN IF THE POWER IS OFF AND THE DEVICE IS UNPLUGGED (ex: by discharging of a large capacitor). Unless you really know what you are doing, don't open one up. i've been trained in servicing electronics, and even i wouln't go near one of these things.



    see: Notes on the Troubleshooting and Repair of Microwave Ovens [drexel.edu] for more information.


    • Re:Microwaves are potentially dangerous---no shit. (Score:4, Informative)

      by Anonymous Coward on Monday July 01, 2002 @01:23AM (#3799009)

      microwaves are high voltage, high current devices. they can kill you EVEN IF THE POWER IS OFF AND THE DEVICE IS UNPLUGGED (ex: by discharging of a large capacitor). Unless you really know what you are doing, don't open one up. i've been trained in servicing electronics, and even i wouln't go near one of these things.

      Good call. If you still feel the urge to work on them, good work habits include wearing good insulated shoes and working with ONE HAND only (other behind your back!), which limits most current paths to just your hand. Usually the worse thing that happens is your hand is tossed off of what you're working, but you're less likely to have a path through your heart, which is when it gets dangerous... Another safety precaution is to discharge the caps with a screwdriver (but be careful, might damage something with a dead short!)
      • Almost all, if not all big capasitors are electrolytic, those things are very sensitive to overvoltage, as well as plugging them backwards. They probably do not like shorting, either. It may not kill you like shock, but being blind because a exploding capasitor threw some metal case fragments into your eyes is not very nice either.

        Just to be sure, as you can't be too careful, discharge those damn things _TROUGH A RESISTOR, NOT BY SHORTING_.

    • Re:Microwaves are potentially dangerous---no shit. (Score:5, Informative)

      by Brymouse ( 563050 ) on Monday July 01, 2002 @01:56AM (#3799091)
      First of all, most large caps is a microwave have 10 meg-ohm resistors on them to bleed off the charge. All you have to do is put a large screw driver across the cap to test if it is safe to handle. If the resistor is in good condition, nothing should happen, if not, you get one hell of a spark. No harm done to you, but maybe the screw driver!

      Now as for servicing a microwave, 9 time out of 10 they have a partial diagram in them, that shows the major componits. Once you have this, it is easy to work on one, as long as you know the basics of how a microwave works.

      Short version of how a microwave works (for food!). First, power comes into the unit, goes through a set-up transformer, is rectified, and smoothed though the cap(s). Then this high voltage is applied to the magnatron (the thing that makes microwaves), and the resulting radiation is couppled into a waveguide. In this waveguide is a metal disk with holes in it, that "stirs" the microve energy. From here it goes into the chamber, and heats your food. It accomplices because the water in food absorbs the 2.4 GHz radiation.

      That's how it works.
      • After following your above instructions and a short trip to the hospital, my lawyer suggested that I get your address.

        Don't overestimate the /. crowd. Describing working with a microwave to 12 year olds is irresponsible!

        Joe
        • Don't overestimate the /. crowd. Describing working with a microwave to 12 year olds is irresponsible!

          Actually, I would say it's a lot more irresponsible to HIDE how a microwave works from 12 year olds. Yes, the microwave is a high voltage device, yes, microwaves can cook flesh, all the more reason to explain how a microwave works and under what conditions they're perfectly safe. (Namely when you leave the door closed, never mess with the insides, and just push the buttons.)

          If you leave people sufficiently curious they might take it upon themself to investigate before they know what they're getting themselves into.

          • "No harm done to you..."

            "...it is easy to work on one"

            "All you have to do is put a large screw driver across the cap to test if it is safe to handle."

            He never even mentions unpluging the darn thing. See, I'm used to not unplugging many of the toys I play with before I work on them (trains, computers, cars). Following the instructions here could kill me. (Of course, after 18 years of "experience", I am learning to unplug and turn off at the breaker, especially when I don't know what the hell I'm doing.

            I agree, teaching someone how things work is great. Implying that working on a microwave is safe with as few instructions as were presented is irresponsible.

            I live in the midwest, when common last words are "Hey y'all, watch this." I don't know that we need any more encouragement here.

            Joe
    • Having looked agin through the article, there was nothing here about messing with the insides, whether the PSU, the maggie or the interlocks.

      Yes, you are right, microwave radiation levels from an oven and the high voltage levels are unhealthy. However these things are usually quite reliable, although there is usually an internal fuse that can blow.

      What concerns me more is that the heat build up from a glowing crucible of molten metal is somewhat more than from a pizza. Such heat isn't going to do the cabling or the door much good.

  • When you are cooking pizza in a microwave oven, it won't reach such great temperatures because pizza is not a very efficient absorber of enrgy, newer microwave ovens have sensors inside to prevent the microwave from getting that hot, and if you removed those sensors, by the time the pizza actually got that hot, it would be a nice balck colour. However, when something such as water ( a very efficient absorber of heat is used ) care must be taken to prevent something such as this [go.com] [abcnews.go.com]. ( Water being superheated then flash boiling when something is placed in it )
    • Been there, done that.

      Thankfully it was only somewhat superheated, leading to violent bubbling and some spill over, and not the kind of violent explosion your link suggests is possible.

    • Re:Pizza won't hit 900 Celcius (Score:5, Insightful)

      by prockcore ( 543967 ) on Monday July 01, 2002 @02:25AM (#3799149)
      Maybe the pizza isn't a very efficient absorber of energy, but the cheese certainly is.

      As anyone who's ever bitten into fried mozzarella sticks can attest.. cheese is the one magic food that has the potential to turn into molten lava.
      • Cheeze contains water!
        Pizza contains water.

        But water evaporates at 100C - once water is gone, the microwaves don't have any materials that will convert the wave energy to heat - thus foods don't really reach temps much higher than boiling. (This is why Mirowaves don't brown things - without metal foils etc.)

        Water Molecules are excited by the microwaves, and are heated.

        Oil on the otherhand isn't heated at all.

        Here's an exp. for you. A few cc's of oil and a few cc's of water in the microwave. Heat for a bit. See which is hot.

        It won't be the oil.

        Cheers!
        • Nonsense. Lots of things in microwaves can get above 100C; the only reason the oil in your experiment didn't is that it's nonpolar, and thus unaffected by the waves.

          Pizza oil contains some suspended polar molecules, so it gets heated; that's why plastic containers used to heat pizza develops nicks. The HOT oil melts the plastic.

          Check out this page [amasci.com] for more info, and goo dlinks to even more.

          -Billy

  • OK. (Score:2, Funny)

    by fidget42 ( 538823 )
    This ranks right up there with using liquid oxygen as charcoal lighter [purdue.edu]. The mpeg [purdue.edu] is quite impressive, though.
  • well, this is fine indeed. I can finally realize my dream of melting basalt at my house. But now what to do with all those old CDs I was keeping to make a solar oven with?

    Info on the elements, OT but close (no bronze or basalt, but iron [speclab.com]: http://www.speclab.com/elements/ [speclab.com] Has melting points and a lot of other data apparently cribbed from CRC.

    P.S. don't forget this [meetup.com]
  • Both waxes are coated with a patent ceramic shell slurry containing some graphite.

    Damn ... now does anyone have an Open-Source ceramic shell slurry mixture?

  • Clothes Dryer (Score:5, Interesting)

    by Anonymous Coward on Monday July 01, 2002 @12:56AM (#3798899)
    Back in 1981, I built a small clothes dryer from a microwave. I drilled a hole in the front glass, placed a vacumm tube through it, with a vacumm pump on one side, and a vacumm flask in the m-wave. I them tested various fabrics with differing amounts of H20 in them. Amazing that a jean leg dryed in 15 minutes, tee-shirt in 5, a wool sleve in 25 minutes (low heat to avoid shrinkage). Based on energy calculations, it used about 2/3 the power and was running at lower overall temperatues (I suspected that local temps ran over boiling, but then again they do in a dryer).
    I wish I had the money back then to persue the idea.
    • I hope the diameter of that hole in the front was less than the wavelength of the microwaves.

      Or you REALLY don't want to stand in front of it for 15 minutes waiting for your jeans to dry!

      I could be wrong about that, but even if some physicist cares to correct me, it's not something I'll be trying any time soon.
    • Water evaporates at lower temperature as the atmospheric pressure reduces. You wanna conserve loads of energy? Pump the air out of the dryer and apply a little heat.

      Oh shit, patent, patent...

    • Great idea until the first article of clothing with a zipper or metallic buttons gets fed in...

      Still, perhaps a dedicated sock/underwear dryer would be of some use. You could make a very small combination unit that would wash, then dry, and spit them out - you'd only need one pair of socks!! Or at least be able to get a clear pair of socks in about five min if you realized you needed to do the wash the night before.

    • Hmmmm
      At my university the microwaves in the student accomodation had warnings on them not to dry cloths as they could catch fire.

      Dunno if there is any truth in that, but I suppose in a microwave without a turntable (yes, these were cheap micowaves!), localised points could get very hot....

      • Yes. Your clothes will catch on fire.
        In a pinch, you can microwave your socks/boxers to kill the little nasties that make them smell funny. Even with a turntable, however, leaving them in for too long *will* result in a fire.

        Not that I speak from personal experience or anything. I, uhm, heard this from a friend.
    • This has already been done. I saw it on tv ages ago. They had a full size prototype. The only problem they said they ahd was with zippers, buttons, etc. Metallic objects caused scorch marks on the fabric.

  • *assuming* that this technique ultimately becomes stable and useable in a home microwave (safety, cost, repeatability, yada yada), this would open up wonderful avenues -- imagine making your own jewelry and robotics parts without building a blast furnace!

    I bet there could also be plastics that would be compatible with this process. Excellent for product prototyping.

    The reality, though, is that it'll never be commercialized to the extent of becoming a hobbyist kit. Too bad.

  • it would be cooler.... (Score:3, Funny)

    by brad3378 ( 155304 ) on Monday July 01, 2002 @01:01AM (#3798920)
    ... if the microwave ran cooler (pun intended).

    If the microwave could somehow have a thermostatic control, I could take a bag of grade-5 bolts and nuke them to a grade-8 tensile strength. The button for 1040-steel alloy can go next to the popcorn button.
    :-)

    To properly control the grain structure of the metal, the heating & cooling processes have to be controlled precisely for temperature vs. time (very non-linear and not instinctive). Introduce a quenching process in the microwave, and I bet you could make some serious bucks selling/operating this thing.
  • They all showed warming, but the granular substance (magnetite) was hot enough to burn the finger.
    Any bets as to how they found this out?

  • Photos overexposed (Score:5, Interesting)

    by dmiller ( 581 ) <djmNO@SPAMmindrot.org> on Monday July 01, 2002 @01:10AM (#3798960) Homepage
    Notice how the crucible and insulating assembly looks over exposed in the photos linked from the article. I wonder if this is because they are emitting a large amount of IR? This would be invisible to the eye, but visible to a CCD camera, even through a the cheap plastic filters they use.
  • Take one green grape (not seedless) and cut it width wise, leaving the skin on one side intact so it forms a sort of hinge. When you lay it in the microwave it should look like a pair of breasts.

    Run the microwave for 10-15 seconds. The grape will spark and then burst into flames. Many all-nighters in college were punctuated with breaks to show people this wonderous phenomenon in the dorm microwaves, and now you too can try it at home. yay.
    • Another fun thing to do is to prove to stupid people how radiation really does cause things to become huge. Put a few large marshmallows in the microwave, and microwave them on high for 2 minutes. The marshmallows balloon up to at least 4 times the size.

      • The marshmallows balloon up to at least 4 times the size.

        Did you ever try eating it then? I've made micromarshmallows as snacks for my friends. It's a lot quicker than a campfire for making smores, and potentially more fun. Try filling an entire bowl with marshmallows. :)

  • Don't Try This at Home, Kids! (Score:5, Funny)

    by Greyfox ( 87712 ) on Monday July 01, 2002 @01:31AM (#3799028) Homepage Journal
    That's what the microwave at work is for!
  • melt iron

    You don't melt iron. You melt -steel-, which is an alloy of iron and carbon, with a variable melting point depending on the carbon content(more carbon, lower melting point).

    The question about the microwave use is not my issue. ;)

  • metal clays are easier to work with (Score:4, Informative)

    by g4dget ( 579145 ) on Monday July 01, 2002 @02:02AM (#3799102)
    If you want to make small pieces of jewelry or other parts, there are metal clays (search on Google): almost pure precious metal (silver, gold) with a little bit of binder. When you heat them, the binder burns away and the metal sticks together.

    Other than that, the technique sounds unnecessarily laborious and complex. There are easier ways to melt metal, even at home. Thermite, for example, should appeal to people who like fireworks. Basic textbooks on inorganic chemistry, mineralogy, and metallurgy can tell you how. (Don't people learn this stuff in high school chemistry anymore?)

    • There are easier ways to melt metal, even at home. Thermite, for example, should appeal to people who like fireworks.

      The problem with thermite is that the resulting metal is going to be horribly impure (yes, I've made thermite, many times).

      Other than having to sit around for several minutes instead of a few seconds, I don't see how the microwave melting method is harder.

      A bigarsed propane jet, on the other hand, would be quite convenient and probably cheaper (electric heating is expensive even when perfectly efficient, and the microwave method was noted as losing much of the supplied energy). A friend has been melting aluminum with this method (why it hasn't burst into flames in his face, I don't know - don't try this at home).

  • Do not try this at home! (Score:5, Informative)

    by Anonymous Coward on Monday July 01, 2002 @02:43AM (#3799200)
    I've cast aluminum (1200F) and iron (2200F) and am truly concerned about the total lack of safety equipment that this guy presented. When I cast the molten metal, we wore complete body leathers and used tongs to keep the hot metal at least 1-2 feet away. To pick up a container using bare hands and sleeves is nuts. Molten metal will burn through unprotected skin.


    A serious problem with pouring molten metals is the risk of moisture in the moulds. For example, if a fly happened to be in the mould when the metal was poured, the metal would explode from the moisture with enough force to hit the ceiling. I sure don't want to be in a room when its raining molten metal!

    • To some extent I share your concern about the lack of safety equipment.

      However, the example you give wouldn't work- any moisture gets cooked off by the microwave in the first 30 seconds- don't forget he's microwaving the mold at the same time as heating the metal; any fly would be dessicated long before.

      However, I'm not saying there aren't other safety issues, any time you have that much heat energy in one place there's potential for catastophic failure. (e.g. what happens if the mold suddenly cracks due to the heat when he's holding it?)

    • Re, Molten metal will burn through unprotected skin....I sure don't want to be in a room when its raining molten metal!

      I have seen it happen on a small scale. One day many years ago we young idiots were casting bullets for the long rifle and poured the lead into the mold while it still had a bit of water in it. It exploded out and a drop of it hit my brother's arm. Yes, it did burn right into the flesh, and that was only lead with its front-porch melting point.

      If its trajectory had been slightly different it would have hit his eye.

      You be careful, now, hear?
    • You're a wimp!
      I'd give you the finger, but I burned all mine off.
  • I mean, this is really cool and all -- but i am sure this is violating an EULA somewhere. ;-) Just be glad that GE is not all up on the M$ behaviors

  • Using Microwaves to combust Aluminium at 1470 C (Score:3, Interesting)

    by cap_pies ( 589407 ) on Monday July 01, 2002 @04:07AM (#3799376)
    Using an industrial microwave (5kW) with Nitrogen piped through a bed of Al powder I got a max of 1470 C before solid Aluminium Nitrate was formed. Temp possibly got up to 1600 C but thermocouple melted. arse. Seemed that key to getting ignition (or melting) was retaining heat. got one reaction at approx 1KW after 15 mins using carbon powder packed between 2 tubes |c| al |c| |c| al |c| Have u tried Au/Ag powders (heat much faster than solids - sorry if already posted)

  • Microwave to heat – best container material (Score:5, Informative)

    by Saggi ( 462624 ) on Monday July 01, 2002 @04:52AM (#3799463) Homepage
    Microwaves in a microwave oven are using a frequency that matches the vibration frequency of the O-H bond in water. Now if a microwave should be converted into heat, it must hit a molecule, where it can leave the correct energy. This is quantum mechanics, so only the precise amount of energy can be transferred to the vibration. If the wavelength of the microwave doesn't match, energy will not be transferred.

    Now the described experiment used several different containers for the metal. These containers absorb the microwave and convert them into heat. To obtain the best container material, you should look for materials whose vibration energy of some of its atom bonding matches that of the O-H bonding in water.

    The O-H bond has been chosen as most food contains water. Materials without water will not heat in a microwave oven. (Unless it contains molecules that match the frequency in other ways).
    • Actually, microwaves will induce currents into anything that is conductive, so it will either absorb microwaves or reflect them. Metals mostly reflect (because their electrical resistance is low), otherwise all you'd need was a plain ceramic crucible.
    • Apparently my microwave's door is made out of that bond. It caught on fire [darkphibre.com] while there was nothing in it!
    • I've heard this before (the claim that microwaves heat the O-H bond in water), but that doesn't make it true. If the O-H bond were the only source of heat, then why can MWs heat things up beyond 100C?

      The simple fact that this person is melting metals proves that there's some other mechanism at work, and further, it's almost certain that this other mechanism is more powerful than the hypothetical water resonance.

      Here is a page [amasci.com] which discusses many "myths" about microwaves, including this one. It also contains some _facinating_ experiments, lots of fun. My favorite is microwaving a light bulb (not listed on that page, but a surprising color light show you can look up elsewhere -- caution, don't try it without the safety precautions).

      -Billy

  • Weaponry (Score:5, Funny)

    by DarkHelmet ( 120004 ) <mark@nosPam.seventhcycle.net> on Monday July 01, 2002 @05:39AM (#3799555) Homepage
    Oh yes, it's a foundry.... Yes, now you can make your own weapons for your Warcraft action figures...

    Oh, you're all geeks.... the lot of you... Not nerds like the site says, GEEKS!

    The worst thing about this is that some of you here will actually think this will Get you chicks!

    Argh! I need my pills? Where are my pills?

  • Knows what he's doing. (Score:3, Informative)

    by WhyteRabbyt ( 85754 ) on Monday July 01, 2002 @06:37AM (#3799677) Homepage
    This guy does know what he's doing though; he's got a patent on an effectively new method of lost-wax casting.

    This could have a lot of implications for small, specialist casters and jewellers. I'm assuming a custom-built microwave foundry would cost just a tad more than a domestic model, but assuming it was built with safety in mind, its probably going to be a hell of a lot more convenient for some people (education institutes) than gas or electric casting overn.
    And centrifugal casters in particular scare the shit out of me; Im always positive the bastards are going to break up, fly apart, spew molten metal everywhere...

  • Safety First (Score:2, Informative)

    by Inda ( 580031 )
    I worked as a Pattern Maker for 8 years and as part of my training I spent many weeks in a foundry.

    A tiny splash of molten metal is very painful, as I'm sure everyone here can imagine. Saying that though, this is nothing compared to an explosion that can happen if any moisture is present in the metal. Superheating even the tiniest drop of water makes it expand - BANG! We used to 'sweat' the ingots for 30 minutes before melting them down. I'm sure a microwave probably heats the metal slowly but you wouldn't catch me playing with it.
    • actually, water does not expand when it getds hot, it contracts. When it turns to steam, then it expands. Minor point, since it would turn to steam almost instantly, but I love pointing out the contradictory nature of water.
      It expands as it gets cold.

  • Microwave rocket engines (Score:3, Interesting)

    by cybercuzco ( 100904 ) on Monday July 01, 2002 @11:47AM (#3800814) Homepage Journal
    This reminds me of a project theyre working on at Penn State. Basically it uses a microwave in a cavity to set up a standing wave to create and capture a ball of plasma. The plasma is then funneled out through a nozzle to produce thrust. I observed a demostration of a prototpe of this engine. Heres how it worked.
    Step 1: Set microwave timer to 60 seconds, high power (they were using a standard off the shelf of Target microwave)
    Step 2, turn on helium flow
    Step 3:Hit start button
    The engine then ran until the microwave dinged and it turned off. They said they usually got only 6 months of use out of the microwave before it burned out, since "It wasnt designed to run a rocket engine"

  • Now you can make your very own! The old US penny is made of 95% copper, 5% zinc. The new ones are 97.5% zinc, 2.5% copper (the zinc is on the inside, the copper is in a thin outer layer). Zinc melts at significantly lower temps than copper...so scratch a new penny down to the shiny zinc, nuke it in the crucible, and out will flow the molten zinc, leaving a hollow penny!

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