OT: uneven cooking in microwaves

[Commander Kinsey]

When will we invent a microwave oven that cooks evenly? There must be some way to install reflectors around the cooking area to randomise the waves.

[Mark]

FWIW Ours does -- it rotates the item being cooked.

[Commander Kinsey]

They all rotate don't they? But it's still very uneven. For the most dramatic evidence of this, put a frozen block of food about twice the size of your fist into the microwave. Heat on full power for 5 minutes. You'll find some parts of the food too hot to touch, and some still frozen. So some bits are being heated many times moreso than others. Presumably one part rotating through a circle is still unheated due to that entire circle being at a node of the standing waves. There must be a way round this. If the microwaves were the thing rotating instead of the food, which I think newer ones do, there could be a non-circular rotation to make things more random perhaps? Or lots of reflectors to make the waves go all over the food.

[devnull]

Maybe you could hang a disco ball in your microwave?

[Brian Gaff]

Philips tried a rotating aerial, I noticed no difference at all except that it rattled as it went around. Brian

[Ed Pawlowski]

None are perfect. One thing people forget or rush is standing time. Some do best with a stir part way. Reheating is usually done best on a lower power setting.

Then there is sugar and fat and how they affect the cooking.

[Chris Green]

Not all rotate the food, there are some which avoid the wasted space of the turntable and thus allow much larger items to be put in the microwave. There's a special name for them which I can't remember.

Well that's just the nature of the thing, the ouside gets hot first, there's no way around that! It is particularly noticeable with large lumps of frozen food, presumably because of simple physics, it takes a

*lot* of energy to melt ice. If my memory of school physics serves me right then it's 160 calories per gram to melt ice, so 'even' heating in a microwave is inevitably going to heat what's already melted quite a lot while melting the bits that are still frozen.

[gfretwell]

The problem is the food itself does not absorb the waves evenly and warmer things absorb more than colder ones, particularly frozen parts.

[Mark Lloyd]

Mine doesn't, and doesn't need to.

[Commander Kinsey]

The whole point of a microwave is it's faster than a normal oven. I don't want standing time, I want to eat when I'm hungry, not after my empty stomach has distracted me for half an hour.

[Commander Kinsey]

Are those the ones with the rotating aerial underneath?

That happens in conventional ovens. But I thought microwaves heated all the way through (well 2 inches I think).

If the heating was perfectly even, and assuming the food was all at the same temperature to start with (which it should be, having been in a freezer for a month), there's no reason anything would thaw first.

[Commander Kinsey]

But if it all enters the microwave at say -20C (from my freezer), then there should never be a warmer thing.

[Commander Kinsey]

Then I assume your waveguide or aerial does. Same effect.

[John]

"Brian Gaff" [e-mail]> wrote in news:qo7ba8$k0v$ [e-mail]:

I wish I could find one with the controls on the top so that the casing was narrower.

[micky]

Not true at all. The exterior 1 is next to air that's 70^F or so, but inside of that 2 it's next to the exterior which was frozen until a few minutes ago, maybe below 32F, as low as 20F in some freezers, and is now just a few degrees warmer than it was. So 2 won't warm as fast as 1 does.

Inside of 2, 3 is even more hidden from the outside warmth, plus it's hidden from the warming 1 layer.

Layers 4, 5, and 6 are like 3 but even progressively more so.

3-6 will warm because of any microwaves that penetrate, but not as fast as what is on the outside.

[gfretwell]

It is just one of those "the faster it goes, the faster it goes" things. If one spot thaws out first, that part will start cooking long before the rest thaws out because as, Chris pointed out, the heavy lifting is the change of state. That is why the "defrost" mode runs at half power or less. It is actually slowing the process in hopes that the heat will spread more evenly. I have figured out that for most things I can thaw them on a thick metal thing like an aluminum skillet with a fan blowing on it faster than the microwave. I don't get hot spots burning before the rest even gets warm.

[micky]

Also the very small ones, found in job snack rooms, usually dont' have carousels. For one thing, heating coffee and soup doesn't require rotation. Liquids stir themselves. And they buy small cheap ones.

Even after mine had a carousel, I would still find some foods heated in a checkerboard pattern, 3-dimensonal checkers. I can't remember details and I'm not sure it's still happening, because I MW different foods now, most often soup.

A checkerboard so it wasn't the kind of substance that made the difference, it was the presence of nodes and antinodes cause by the intersection of waves from different directions. MW's also already had something in the top to scatter the waves around, but it wasn't enough.

I can't imagine why the carousel didnt' eliminate the checkerboard and I wish I knew for sure if the current one does do that, or not.

It is particularly noticeable with large

[gfretwell]

Microwaves have gone through the same transition as monitors. They are short and wide now instead of being more "square". My old 1971 MW was more of a 4x3 thing and fits in a narrower space.

[micky]

Standing time after heating will allow heat to even out, but I think the inst4ructions call for it mostly so people won't burn themselves and sue them. I never wait a minute. It takes 10 seconds to take the food from the oven to the table, 5 seconds to take off the top, 5 seconds to get a fork,and by 30 seconds I'm eating. I like the food to be warm or hot. I'm careful not to burn myself and if I do I won't sue them.

Good point. A lot of instructions say to do that, and if it were only that different substnaces heated up differently, stirring would not help. They are trying to eliminate the checkerboard. BTW, I'm too lazy to get up and stir, so I don't, and it comes out pretty well.

[micky]

Even with a minute standing time it's still a lot faster than a normal oven. But I don't wait.