The heating technique of the oven is quite unique. It uses dielectric heating to heat water, and other such polarized molecules present in the food, and helps to uniformly heat the food. The invention dates back all the way to World War II. Since then, it has undergone many changes, before reaching its present form.
It was only accidentally that this technology was stumbled upon. Dr. Percy Spencer, an engineer with Raytheon Corporation, is credited with the invention of this modern-day marvel. He invented this amazing kitchen appliance in 1946 while working on a research project about radars.
While conducting a test for a special kind of vacuum tube called a magnetron, he found that a candy bar kept in his pocket had melted. He was curious to know if it was in fact the heat from the magnetron tube that caused this.
So, he placed some popcorn kernels close to the tube, and observed it closely. After a few minutes, to his amusement, he found that the popcorn started cracking, and popping all over the laboratory.
The very next day, he and his colleague came up with the idea of placing an egg in front of the magnetron tube. Again, they found that in no time the egg started moving because of the high internal pressure caused by the rapid rise in temperature inside it. Finally, the egg exploded, and splattered all over the face of his colleague.
Thus, he concluded that the low density microwave energy could be used to cook food. Although they ended up with an egg in their face, that definitely wasn't how they felt about their invention!
For the final inference of his observation, Dr. Spencer used a metal box in which he fed microwave power in order to create a high density electromagnetic field. The food was placed inside the box. The result was exactly the same, and the food heated up in no time.
The First Model
On October 8, 1945, Raytheon Corporation filed for its US patent for Spencer's microwave method of cooking. A specimen of this oven was kept in a Boston restaurant for testing. In 1947, Raytheon Corporation developed the world's first microwave oven, and named it Radarange.
It was huge, much larger than its present form. It was about 1.8 m (6 feet) tall, and 750 pounds or 340 kg in weight, and was priced at $5,000. The magnetron tube of the oven needed water cooling, hence, plumbing installations was also included in the oven. Power required to run the machine was as high as 3 kilowatts!
The first commercial model of the microwave oven came up in 1954, but it did not do well in terms of sale. In the year 1965, Amana Corporation was acquired by Raytheon, and they developed the first home model of Radarange in 1967.
It was priced at $495, and became quite popular despite the fact that the sales were quite slow at the start. This marked the beginning of a whole new concept of cooking.
In the 1960s, another company called Litton, came up with a new model of ovens, which were short and wide in shape, and looked quite similar to the present model of microwaves. This model was constructed with a unique magnetron feed which helped it to support itself in a no-load condition for an indefinite period.
It was first exhibited at a trade show in Chicago, which saw its sales grow at a very rapid pace. In the 1970s, their sales grew at an even faster rate, and by the end of 1975, crossed 1 million in the US market.
Around this time, Japan developed a much cheaper variety of microwaves using a re-engineered magnetron which was a lot cheaper that the conventional magnetron.