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.

[Brian Gaff]

The problem is that the inside of a microwave oven is going to have standing waves in it, where these cancel out you get a cool spot. That is supposed to be fixed by the turntable, but unfortunately some ovens have a cold spot right in the very middle of the turntable and hence that bit gets cooked only be the heat in the rest of the food, the old leave to stand instructions are to help with this. Also of course the density of the stuff being heated and what it is made of , ie water heats, but I notice pastry on apple pies often won't resulting in very hot apples and cold pastry!

I guess if you used various wavelengths you might get a better result but if the material is almost transparent to the frequency, it just won't get hot. Brian

[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.

[whisky-dave]

That's why quite a few things say stir halfway through cooking time.

If someone is willing to pay for such a thing perhaps they'll make one. not sure whether the industrial ones or those in canteens heat any differntly. I'm not sure how much extra I'd be willing to pay so I don't have to stir halfway through.

[Mark Lloyd]

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

[Commander Kinsey]

Various wavelengths sounds like a good idea, I wonder why they don't do that? Maybe only one very precise wavelength is any good at heating water?

In mine (with a rotating turntable) I get cold spots that are not in the centre, so presumably the standing waves have a cancelled out bit all the way round the rotation, say 2 inches from the centre.

[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]

And why I asked if something could be done to improve the oven so we didn't have to. Microwaves are for convenience. If I was a chef, I'd be using a normal oven.

Microwaves are pretty cheap (£30 starting price!), and plenty folk would pay £300 for a really good one. Surely for 10 times the price they could make something good?

[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.

[whisky-dave]

What wavelenghs, want to try audio, perhaps visable for photosysnthesies.

No a small range perhaps then others might comflict with other radio waves such as wifi routers which work on similar frequesncies around 2.4GHz.

could be that that section contains less water.

[whisky-dave]

I've yet to see a standing time of longer than about 1 miniute, and I manage to do other things during that time.

[whisky-dave]

Sauucepans of stuff like sauces still need serving , some need whisking.

Not sure how many would spend £3k on a microwave.

[Mark]

You can use either. Horses for courses.

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.

Really? I'm not convinced.