I’ve been wanting to do a series of posts on Fun Things To Do with a Microwave, and I’m just going to get off my butt and DO it!   For some of these to work well, you need to know where your microwave hot spots are.

What do we mean by hot spots?  Microwaves are just one form of radiation — like x-rays or visible light — of a particular frequency.  The reason they chose microwave frequencies for ovens is that this frequency is more readily absorbed by water.  The microwaves are pretty long (about the size of a grape, as you’ll see in the next post), so you get a regular pattern of peaks and troughs (or hot and cold) as the waves add and subtract  (it’s a checkerboard, like two-slit interference).  You may have noticed that food cooks slower at the center of a microwave and faster at certain other places (that’s why those rotating plates are handy).

Method 1:  THE WATER METHOD  (From RealSimple)

You can find the hottest parts of your microwave by placing custard cups or small bowls filled with water all around the oven. Heat for 1 to 2 minutes, checking every 30 seconds. The ones that boil first are in the hot spots.

Method 2: FAX PAPER gives a more permanent map (from Barnesos.com)

Take a damp paper towel and place it on top of 5-10 other paper towels in the bottom of your microwave. On top of it, place a sheet of themally sensitive fax paper, the kind that old crappy fax machines use. Credit card recipts also work, but they’d be harder to tile the bottom of your microwave with. The extra towels at the bottom provide some insulation. Turn the microwave on for a while. The first areas on the paper to turn dark are the hot spots.

Method 3: MARSHMALLOWS (or chocolate chips)

Or a tasty way is to place marshmallows all over the bottom of the oven (might want to put a paper towel down first).  Greater pixel resolution with the tiny marshmallows (more Marshmallows Per Inch!)

Here’s a kid-friendly explanation of microwaves (as well as a simulation of the marshmallow method) and a kid-friendly explanation of hot spots.