Microwave ovens are wonderful things. From virtually non-existent, 35 years ago, they've since reached the point of being a standard part of nearly everyone's kitchen. And for many things they are far more convenient than a regular oven.

But the mode of cooking is different. An oven uses convection and/or IR radiation. A microwave uses, well, microwaves. What it does is to pump hundreds of watts of a particular frequency into the oven area. The frequency is one of the resonant frequencies of water molecules, which are polarized and will try to flip over and over to stay in tune with the field as it changes. There is resistance to this, and the resistance turns to heat.

Which is why last night's pizza heats and the plate does not. There's no water in the plate.

Microwave TV dinners soon became a staple (at least around here). But I also love meat pies. And cooking a crust in a microwave oven is really a problem

It's one they solved, though, and I consider it one of the niftiest inventions that people use and few people even notice or understand.

If you have bought a microwavable meat pie, you may have noticed that the carboard pan it comes in is gray, kind of strange looking. The cooking instructions say that you're to leave the pie inside its box, and inside the box, on the top, there's a piece of paper which is crosshatched with the same gray color.

What's going on is that the tray, and paper, are conductors. The microwaves set up eddy currents in conductors, which is why a CD in a microwave oven comes out looking really weird. (DO NOT DO THAT; it's not good for the oven.) It's why you can't use a plate that has gold trim; the plate will get wrecked.

But the gray pan the meat pie comes in is also a resistor. The eddy current tries to move back and forth, as the field oscillates, but the induced current is running through a resistor, and the result is heat in the pan. And it gets hot enough to radiate significantly in IR, which browns the crust on the sides and bottom. The reason for the paper on the top is to brown the top of the pie.

It never used to really work correctly for me. Some parts of the pie would get burned and other parts didn't really get brown. And the pie always stuck to the pan afterwards; I'd have to scrape it loose with a spoon.

A couple of months ago I found out why. My first microwave oven was only 800 watts. I had that for 20 years. The second one, from three years ago, was 900 watts. The new one I got recently was 1100 watts. It was also a name brand (Sharp), and likely had a better, more even radiation pattern.

But the power is the real difference. More radiated power means the pan and paper get hotter, and that seems to be critical. All the pies I've cooked with the new unit have been gorgeous:

And they've all come out of the pan intact, too. It's awesome.

(You can tell that I'm hard up for things to post about, can't you?)

UPDATE: Could be worse; could be me talking about my server. Speaking of which, since I opened it up and blew out all the dust and lint, I haven't had a single heat fault. It's only rebooted once, and I did that because I always have to reboot the server when I power cycle my cable modem.

Posted by: Steven Den Beste in Daily Life at 07:29 PM | Comments (10) | Add Comment
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