Back just after World War II, the legend goes, Dr. Percy Spencer was working on some radar-related research with an item called a magnetron tube. At one point, he realized that a chocolate bar in his shirt pocket had melted when he was close to the tube. Being a good, distractible scientist, Spencer quickly arranged a set of rough experiments to test this new phenomenon ... one of which ended with an assistant getting pelted with bits of exploded egg.

It rapidly became clear that any foodstuffs placed near an operating magnetron got hot VERY quickly. It wasn't long before Spencer refined his idea to making a metal box in which to focus the microwaves emitted by the magnetron -- and the earliest microwave was born.

Now, the very first microwave ovens were a far cry from the Amana perched on your kitchen counter. They were almost 6 feet tall and weighed almost half a ton. The first magnetron tubes were water-cooled, so the plumber got his pound of flesh along the way, too.

Over the years, advancements in both the technology of and the uses for microwaves took great strides. In 1975, sales of (now countertop) microwaves surpassed those of gas ranges, thus officially making microwaves a part of a well-equipped kitchen.

How Do They Cook?

There is a common myth that microwaves cook food from the inside out, that it's possible to have food done to a turn on the inside and raw on the outside. While it's an understandable misconception, the truth actually is that cooking starts JUST below the surface of whatever your foodstuff is.

Let's say you're cooking a chicken drumstick. The magnetron emits microwaves, and another device (different models use different things) "scatters" the waves as they enter the oven, so they hit your food from a myriad of angles, rather than striking just one spot like a death ray. The metal box of the interior and the metal grid in the door reflect the waves, turning the interior into a sort of radiation pachinko machine, with "balls" flying in all directions.

When the waves strike your food, they agitate the molecules in it and are converted to heat (NOTE: this is why microwaved food doesn't become radioactive, the waves become heat). The heat begins to spread both inward and outward.

By far the most common molecule in almost any foodstuff is water, which is why you get so much steam in microwave cooking. That steam also illustrates one of the shortcomings of microwaves: they can't really get food much hotter than the boiling point of water without becoming carbonized lumps. Thus, a microwave is NOT the weapon of choice if you wish to brown or sear meat.

I know, I know, the Hot Pocket you had for breakfast had that nifty "crisper sleeve" with a metallic lining that makes the crust nice and crispy. Believe me, it takes FAR more heat, and for far longer, to brown a steak.

Exploding Water

This brings us to the topic that sparked me to write on this topic this week: exploding water. This was once thought to be an urban legend, but countless video duplications of the phenomenon, along with some hard science, have proven that it's possible.

How does it happen? When you heat water, it needs some tiny imperfection either on the interior of the container or on the surface of the water to allow bubbles to form. So, if you've got an incredibly smooth container and nothing disturbs the water's surface, it is possible for the water to become insanely hot without boiling.

When you break the surface tension of this superheated water, it reacts violently, spraying upwards of 10 feet and causing burns on unsuspecting kitchen inhabitants.

There is a dead simple way, however, to make sure this never, ever happens to you. Use a chopstick. An ordinary wooden chopstick (or bamboo skewer or any other food-safe wooden stick) placed in your water pitcher will provide a lovely imperfection around which the boiling can begin.

Granted, the likelihood that you will ever encounter this phenomenon is very small, but the damage caused when it DOES occur makes a small precaution like a chopstick seem eminently prudent.

Got a question? Comment? Topic you'd like to see covered? Drop me a line, anytime!