Microwave Rundown

Dear Home Ec 101,

How does a microwave work? Also, if you’re not supposed to put metal in a microwave, why do my Hot Pockets™ come with a foil lined sleeve?

Signed,

Dyspeptic in Des Arc

Heather says:

I have some deliciously geeky friends who will probably rip the explanation I’m going to give you to shreds, but I want them to keep in mind I’m trying to break this down to as simple a concept as possible. I’ve talked about the manner in which heat is transferred before. With conventional ovens, you have indirect heat, the heating element heats up the air which then heats up whatever your’re cooking. Your stove is an example of direct heat, your burner heats up the pan which is in contact with your food. Now please don’t get all weird on me and say, “But Heather, the burner isn’t touching the food, so how can it be direct?” Pans are simply a convenient way to transfer the heat and keep the mess under control.

So, what about microwave ovens? Microwaves are electromagnetic waves, just like radio waves or visible light, the difference is the length. Your microwave has an antennae that broadcasts these waves inside the appliance.  How come the waves don’t go right through the glass? The waves don’t escape because you don’t need a solid wall to contain them, think about how a tennis court typically has a chain link fence. We can see through it, but the holes in the fence aren’t large enough to let the tennis ball escape. It’s the same principle.

I know a droplet of water is round, but the molecules it contains aren’t. Individual molecules of water are bent, almost like a V. The two hydrogen atoms would be the positive side and the oxygen atom creates the negative. Since opposites attract, this keeps individual water molecules hanging out with one another. The microwaves broadcasted by your appliance excite the water molecules in your food causing them to flip back and forth.  Rub your hands briskly together for a moment and you create heat through friction. Your microwave heats your food by creating friction between water molecules and the molecules they are in contact with. This is why if you heat a glass of water in the microwave the water can boil before the cup gets hot. If you let the water sit in the glass for any extended period of time if would heat through conduction or contact with the hot water. It’s not the microwaves interacting with the glass.

• Covering food in the microwave helps it heat faster by creating a pocket of steam; it also contains the splatter.
• Stir food that has been microwaved to ensure there are no hot or cool spots.

Now some of you may be saying, aren’t microwaves dangerous? Why don’t you use yours more?

For me, it’s mostly a texture thing. It’s the same reason I don’t steam a lot of foods. I prefer the magic that happens when food is seared or the crusty perfection of baked goods. When it comes to microwaving, use common sense and don’t use plastic that isn’t designed for the appliance. The plastic may melt partially during cooking and leach chemicals into the food. To play it safe, I try to only microwave in glass or ceramic.

I’m not sure whether to address the issue of metal in a microwave or the fact that you are eating Hot Pockets™ -Whoops, there goes another potential sponsor, right?

It’s not the metal that causes the problem, but the shape of the metal. -It’s not you, it’s me.-  The problem is arcing, or the build of  a charge that jumps from one point to another. It’s like a miniature thunderstorm in your microwave. Create enough mini-lightning bolts and something will get zapped. Your Hot Pocket™ sleeve is flat, it reflects the microwaves back to the crust of your food and to the fat in the pastry which also gets excited, this creates enough heat to brown your snack.

Questions?

Tagged as: Cooking Basics, Reader Questions