A longstanding and peculiar myth about microwave ovens, that microwaves cook food from the inside out, got started at the very beginning of the microwave oven industry. It was based on the observations of Dr. Percy L. Spencerof the Raytheon Corporation.
The company had worked on Radar during World War II, but in 1946, Spencer, more or less by accident, hit on the idea of cooking food with microwave energy. He had been testing a magnetron, which is the device that emits the microwaves. Taking a snack break, he noticed a chocolate bar in his pocket had melted, even though the day was cool. Thinking that maybe it had to do with the magnetron, he aimed it at some popcorn kernels. They popped. Then he tried a raw egg. It exploded. Why did the egg explode? Steam pressure built up within its shell. If steam pressure could build up within the confined shell of an egg so quickly that it exploded, what does this mean? It must mean that the microwaves are cooking the inside part first.
The Raytheon Corporation, after this discovery, developed the first microwave oven, the RadaRange. The first oven was to be named Radar Range, based on a name submitted by a contest winner. This was changed to Radar Range, and then the words were combined to get “RadaRange.” The first used 220 volts and had it’s own internal water-cooling system, which meant it needed its own water supply. The first unit was sold to a Cleveland restaurant in 1947. That model cost around $5000 and had a pull-down door. It was almost six feet high (5 feet ll inches), and weighed 750 pounds.
These early units were only used in large-scale food operations like restaurants, cruise ships, military ships, etc. Later commercial models in the early 1950’s cost from $2000 to $3000 and were still quite large and cumbersome. Raytheon did not market microwaves directly to consumers, but instead, it licensed other firms such as Hotpoint, Westinghouse, Kelvinator, Whirlpool, and Tappan. It was not very practical, by the way, being the size of a refrigerator and weighing over 700 pounds, while only being able to cook the same amount as modern microwaves ovens.
The company soon improved the design and, especially, the size, and the boom was on. Later, the company found that microwaves pass through all sorts of materials. When the waves pass through, they don’t do anything. They don’t affect the material. But when the waves are absorbed, as in the case of water, we get heat.