[ams6110]

In my experience they heat the outside but the center warms by conduction.

If I heat a bowl of tomato sauce it can be boiling at the edges and cold in the middle. I have to stop and stir it a few times.

Same with potatoes. Hot on the outside, raw in the center.

[jerf]

So I went poking around on the Intarwebs for "microwave penetration" and found this rather intriguing page with penetration depths of various items: http://www.pueschner.com/en/microwave-technology/penetration...

I was surprised by the table. Temperature matters way more than I'd expect for water, and it seems ice may in fact be effectively transparent to microwaves? Now I want to fiddle when I get home... it looks an awful lot like you can put a cup of water and a chunk of ice in a microwave and boil the water while the ice is still frozen... (though I'm going to assume that number for ice is pure ice; air bubbles in ice may wreck this up) Experimentation time!

[stcredzero]

Someone came up with a recipe exploiting the fact that microwaves are absorbed much more readily by fluids than solids. It was a frozen meringue with a hot center. I think it was in Sci Am. The name suggested the reverse of a Baked Alaska.

[telchar]

Now that's some clever cooking. I'd not have thought of that.