"It would have to be food-grade, high temperature AND not absorb microwaves itself."
How about a plastic similar to a bowl you would heat soup up in... in a microwave ? Lets not make this more complicated than it is.
"So ... there is a difference between nuclear radiation and microwave radiation, and that does not mean that microwave radiation is safe! Sure the debate is out there regarding cell phones, but don't forget that cell phone only transmit a few watts of power versus the 1300W of power in your oven!"
Lets put some numbers to things. Lets say the power radiated out of the two holes is proportional to the hole surface area divided by the total surface area of the inside of the oven. Reasonable assumption ? Actually it will probably be less than that, because the water coils will absorb a most of the energy, but lets neglect that.
I just measured a microwave and it is 13.5" x 14" x 7.5". So the interior surface area is 2 x 13.5x14 + 2 x 7.5 x 14 + 2 x 7.5 x 13.5 = 790 in^2.
The area of our 2 holes is 2 x 0.375^2 pi/4 = 0.221in^2
So estimated radiated power would be 1300 watts x 0.221/790 = 0.3632 watts.
Now that assumes that the water doesn't absorb any of the microwave power leaving those holes.
"Also, water is a dielectric and not a 'perfect conductor' the way the mesh is in the faraday cage."
I never said that water was a perfect conductor ! Here is an absorption curve for water for various wavelengths. A household microwave runs at about 2.5 GHz. Its wavelength is about 300x10^6 / 2.5x10^9 = 8 cm
"If you poke a couple of holes in your microwave oven, and 'fill' the holes with water, you attenuate the leakage, sure, but you are still going to have lots of leakage, and at that power level there can be health impacts over a period of time."
Do you have any math to prove this or is it just a wild guess ? Did you read all of the post and see that my approach would be to measure a few things as we went along ?
"And even if someone wants to debate the health impacts, the faraday cage is also there to keep the emissions below FCC requirements, so if you increase the emmisions you are actually breaking government regulations (the requirement is international...)"
Yeah, the FCC police are going to shut me down for radiating less power than a cell phone !
"If you put a metal coil inside the microwave oven, you will get some REALLY high potential (voltage) differences at various points around your setup, and you will have a REALLY cool light show due to all the breakdown and arcing. Remember what your mom always told you - don't put anything metal in the microwave!"
First of all, if you watch Mythbusters, you would find that not all metal objects arc. Secondly, if you looked at my illustration, it clearly labels the coil as PLASTIC !
"I do honestly enjoy and respect the ingenuity homebrewers show, but sometimes creativity can be dangerous. This is a really clever setup, but it is not worth the risk."
And you have made that determination how ? Did you do some math or experimentation ? Are you an expert in microwave radiation ?
"You'd be better off running a coil through a pot of hot/boiling water on a hot plate and controlling the heat that way."
Otherwise known as HERMS and if you look at my sig, you will see that I have a HERMS setup now. Or one could inject steam in the mash and if you look at my other posts you will see that I am working on that too.
"I think all of them are pretty much duty cycle 'variable' power, at least for the home consumer."
Did you follow the link I provided for the microwave ? The Panasonic models are called inverter microwaves and they modulate the power level of the microwave unit, not simply turn it on and off.
Are people out to constructively contribute to this idea or shoot it down outright ? Lets keep an open mind about things and quantify the risks before we get our panties in a knot.