
Microwave Oven Diagnostics with Indian Snack Food - gus_massa
http://www.evilmadscientist.com/2011/microwave-oven-diagnostics-with-indian-snack-food/
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joezydeco
_" Did you know that if you take apart microwave ovens, there is a really
great ceramic magnet inside of the magnetron?"_

There is also beryllium oxide in the ceramic insulators of most magnetrons. If
the insulator cracks or is broken, that dust is highly toxic if inhaled.

If you want a nice magnet, there are safer ways to get one. Leave the
magnetrons alone.

~~~
cellularmitosis
Anytime I see someone mention hacking on magnetrons, I feel it my duty to
remind us that the back of your eyeballs don't have pain receptors. If you
were to power up thatagnetron outside of the microwave and point it at your
face, it's possible you'd blind yourself before you even realized you were in
danger.

~~~
asteli
IIRC, the danger is actually to the /fronts/ of your eyeballs, the result
being cataracts rather than retinal damage.

~~~
stenl
And the front (cornea) has more pain receptors per surface area than any other
part of your body. Not that this would necessarily help prevent cataracts if
you expose your eyes to a magnetron.

~~~
bjelkeman-again
I didn't realise this until I had laser surgery to correct a cornea problem.
Oh dear, two days in a dark room on morfin, before I could even think straight
again, no fun. But now I can see better again.

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sombremesa
I just tried this with papad(ams) and this is what it looks like at 30
seconds: [http://i.imgur.com/oclJIS9.jpg](http://i.imgur.com/oclJIS9.jpg)

I'm guessing 30 seconds is too much for these. (Although you can kind of see
that my hotspots match #1 in the original article)

~~~
blahedo
Experiment replication: one of the core requirements of scientific
exploration.

Hooray science!

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akjetma
All these microwaves just need a more complex 'plate spinner' that actually
translates the rotating plate across field lines. Kind of like a spirograph...
[http://i1216.photobucket.com/albums/dd371/benice_chen/hypo_h...](http://i1216.photobucket.com/albums/dd371/benice_chen/hypo_hypotrochoid_001.gif)

edit: nevermind, didn't realize they kept the 'plate spinners' on during the
experiment. The rings in the appalam are artifacts from rotating an anti-node
through the food. would have to do something different to get equal heating
using ~two points vs. a line

~~~
SomeCallMeTim
Like a slow-speed random orbit sander? :) [1] Some of the dead areas looked
too big for even that to help, and it would mean the maximum plate size would
be smaller. Hmm...

OK, I'm going to say that the right answer is to move the microwave source
linearly (or change how it's aimed? Or otherwise change its focus) at a
frequency that would maximize even coverage of the heating area based on the
rotation speed of the turntable.

Another (more limited) possibility is a way to mount a fixed spoon that could
stir soup or other appropriate liquids while the bowl turned.

[1]
[https://en.wikipedia.org/wiki/Random_orbital_sander](https://en.wikipedia.org/wiki/Random_orbital_sander)

~~~
TheLoneWolfling
Many microwaves do something similar - they have a spinning "fan" that's
designed to perturb the standing wave pattern.

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chris_va
This is actually a fun way to measure the speed of light. You can measure the
wavelength by looking at the distance between the bubbles. That plus the
operating frequency of the microwave will give you the phase velocity.

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anigbrowl
I got rid of mine several years ago and have never once found myself thinking
'gee, I wish I still had a microwave.' You know what takes up less space,
saves money, and provides constant utility, which most American kitchens don't
have? An electric kettle. The most appliance-happy country on earth (except
maybe Japan) and you still boil water on the stove like it's 1815.

~~~
snarkulosity
I've heard that electric kettles don't work as well in the US as in (say)
England because our mains voltage is much lower -- and I guess a transformer
would be too bulky.

~~~
jarvist
I think this is probably true - in the UK (and EU) our kettles are 3 kW,
maxing out our 230 V / 13 A plug/sockets.

American plugs always seemed relatively anaemic (and scary dangerous - where
are the switches? where is the Earth? though the EU are also typically
unswitched), though you do get to have less bulky mobile phone chargers as a
result!

~~~
weaksauce
> (and scary dangerous - where are the switches? where is the Earth? though
> the EU are also typically unswitched)

well the bottom prong on a cord is the ground and anything that is not a
wallwort is polarized nowadays so that the neutral and hot are always on the
right wire.

by switched you mean it has a fuse in the plug? if so that's not something
that america does. we have 15A circuits going to different parts of the house
and if there is a possibility of water immersion there will be a GFCI circuit
breaker or outlet installed to protect all downstream outlets. overall it
works well enough that there aren't a massive number of deaths caused by it.
usually you have do something exceptional to be electrocuted.

edit: the kettle I have is 1500 Watts and at 120 volts it's ~12A of current.

~~~
jdhzzz
Kitchen and dining room circuits are required to be 20 A and GFCI in the US so
you could up the wattage if need be. I doubt such a thing exists, though.

~~~
DiabloD3
They are NOW required to be that, but a lot of legacy circuits are still 15A,
and some even don't have GFCI (GFCI only became a requirement in the late
70s/early 80s in the kitchen, bathroom, and anywhere else that can conceivably
be near water.

This has spread to AFCI (arc fault instead of ground fault) being put in every
bedroom as a requirement as well.

If your house doesn't have GFCI and AFCI everywhere, they're required, you
proobably should start retrofitting your sockets.

All of that said, you can use temporary use 1800W devices on 15A legally
without tripping the breaker.

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dbbolton
My microwave has a feature that when you press the "Start" button without
entering a time, it just runs for 30 seconds on high.

One time I hit the start button and it started running based on the value of
the clock (e.g. it was 4:23pm and the oven kicked on and counted down from 4
minutes and 23 seconds).

I suppose it could have been a weird coincidence, but my partner is very
strict about leaving "unused time" on the microwave and obsessively hits the
Clear button. Plus it seems unlikely that there would be that much unused time
left (it's usually a few seconds), or that I happened to use the microwave
exactly when the unused time synced up with the clock.

~~~
mortenlarsen
> but my partner is very strict about leaving "unused time" on the microwave
> and obsessively hits the Clear button.

The same here. She gets really mad about that. I can't really blame her, since
I am am just the same about a bunch of other stuff.

~~~
w-ll
I'm the one that hates it.

My microwave is my most visible clock in my apt (small sf sub). Whens its
paused it doesnt show the time and just constantly blinks.

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latcampbell
I make appalams in microwave too and have the same uneven cooking problem -
putting them vertically seems to help. Here is a commercial product that says
so too. [https://www.papadumexpress.com](https://www.papadumexpress.com)

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sjtrny
Most things your microwave aren't so flat though. Usually they have a bit of
height which reduces the uneven heating somewhat.

But even for heating flat items (such as Naan) I haven't noticed any uneven
heating with my giant Panasonic microwave.

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anonetal
xkcd had a nice what-if on this recently ([http://what-
if.xkcd.com/131/](http://what-if.xkcd.com/131/)). He points to the way ice and
water react to microwave radiation as one of the main culprits for uneven
heating (of frozen stuff).

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jpalomaki
Previously I've seen similar tests done with oatmeal and sugar. Put oatmeal on
plate and then sprinkle sugar on top. The purpose of the oatmeal is to
insulate. The sugar should get brown on those places where the microwaves hit.

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wierdaaron
You can do the same with sliced cheese, I've heard.

~~~
Luyt
If you microwave slices of smoked cheese (on baking paper), they become crispy
crackers (lowcarb, even).

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minthd
That seems like a useful thing for a small crowdsourcing site to. It's useful
information to know before buying a microwave.

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danellis
Cooking them in a pan of hot oil is _so_ much more satisfying anyway. They
double in size in about a second.

~~~
geon
And taste much better.

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aioprisan
Can't you just coat them lightly with oil? That ensures that they get heated
up more evenly.

~~~
lake99
True, and fried appalams are tastier anyway.

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castratikron
What would happen if they raised the plate a few inches from the bottom? With
this experiment they're only looking at a cross-section of the wave.

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wyc
Receipt paper could serve the same heat-sensitive purpose and might be easier
to find.

~~~
officialjunk
dry heat-sensitive paper won't work; microwaves work by resonating with water
molecules to vibrate them and cause them to heat up.

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lvs
Uhh... you think water is the only molecule with a dipole moment?

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officialjunk
of course not. you're right, i should be more general an say any electric
dipole, but what i was trying to point out was that microwaves don't directly
radiate heat and instead vibrate/rotate certain molecules. so, heat sensitive
paper isn't going to work, unless there's some that have dye that will
interact with a microwave.

~~~
wyc
enjoy:
[https://www.youtube.com/watch?v=3O2QhnXm10E](https://www.youtube.com/watch?v=3O2QhnXm10E)

