War Heritage Institute

No radar, no microwave!

All present-day kitchens are equipped with a microwave oven. An estimated 200 to 300 million of them are used all over the world. Let’s retrace the success story of an appliance we deem indispensible in modern life.

The name of Percy Spencer no longer rings a bell with anyone today, some innovation specialists excepted. However, the American engineer undoubtedly deserves double recognition: he not only contributed to the allied victory over Hitler, but also liberated housewives in the ‘70s. While working for the Raytheon company Spencer first discovered how to produce a major military invention – the radar – on an industrial scale. A few years down the road his research led to the appearance of the microwave oven.

A US Navy medal

The history of the microwave oven and Percy Lebaron Spencer’s destiny are intrinsically linked. Nothing predestines this man to become a brilliant engineer. He loses both parents at the age of eighteen months and is raised by a very poor uncle. He quits school when he is twelve and starts working as a factory machine operator.

The arrival of electricity and of the telegraph in his small Maine village turns his life upside down. Fascinated by both technologies he is selected to supervise the electrification of a factory and then enrols with the Marines as a telegraph operator. He spends all his nights learning about inventions and techniques.

Percy Spencer is demobilised in 1918 and spotted a few years later by Raytheon, a young company born out of the Massachusetts Institute of Technology (MIT) specializing in electronic tubing. When the United States step into the war Raytheon signs a top secret contract for the industrialization of a British invention: the radar, an appliance flawlessly detecting German ships and airplanes.

In 1945 Percy Spencer in that way works on a magnetron tube, a contraption transforming electrical power into electromagnetic power through microwaves. He has to simplify the production process of that element, in order to optimize the build of military radars. Thanks to this innovation, production of magnetrons jumps from 17 a week to 2.600 a day and Raytheon ends up supplying 80% of all radars used by the Allies. The company becomes a true giant in defence circles and Percy Spencer is decorated by the US Navy.

Chocolate, popcorn and eggs

Once peace is restored the market for military equipment plummets, which gravely endangers Raytheon’s economic equilibrium. Percy Spencer then displays an incredible inventiveness. A chocolate bar melts in his pocket when he is using a magnetron tube, which sets him thinking. He is intrigued and has another go with corn: he obtains popcorn. He then decides to place an egg in an open jar in front of a magnetron tube: the egg explodes. He notices that the inside of the jar heated more quickly than the outside. From that day onwards, Percy Spencer heats his lunch using a magnetron.

Several scientists have by then already observed the heating powers of microwaves, but Percy Spencer is the first one to apply this particularity to food.

150 licenses

In late 1945 the engineer takes the first license on a microwave oven and Raytheon starts producing it in 1947 as the “Rader Range”. However, with its 1 m height, its 320 kg weight and its hefty price (3,000 $), the appliance is not a success. It is only by 1967, two years after having taken over Amana Refrigeration, a white-goods company, that Raytheon launches a microwave oven for domestic use priced 500 $. That will gradually enter American homes.

In 1971 the Food and Drug Administration imposes norms on constructors and in 1971 sales of microwave ovens for the first time exceed those of gas ovens. The household appliance conquers the world in the following decade.

Percy Spencer can unfortunately not witness the success of his invention. The self-taught engineer indeed passes away in 1970, aged 76. He then has 150 licences in his name. The University of Massachusetts grants him a posthumous PhD. He enters the National Inventors Hall of Fame (USA) in 1999.

In short:

  • 1939: creation of the magnetron, an instrument producing microwaves;
  • 1945: Raytheon deposits a licence for a microwave oven;
  • 1947: Raytheon launches the Radarange, the first microwave oven;
  • 1967: commercial launch of domestic microwave ovens;
  • 1975: worldwide sales success.