Percy Spencer invented the microwave oven after observing that a candy bar in his pocket melted near active radar equipment during his work developing radar technology for the military during World War II. He experimented by microwaving popcorn kernels and other foods, creating the first microwave oven from a high-density electromagnetic field generator enclosed in a metal box. Raytheon patented and first sold the large and expensive Radarange microwave oven commercially in 1947. It was not until 1967 that a reasonably sized and affordable countertop microwave became generally available for home use.

1. The Invention of
the Microwave!

2. Percy Spencer, the inventor of the first microwave oven, perceived his idea after World War II from radar technology
developed during the war. Named the Radarange, it was first sold in 1947. Raytheon later licensed its patents for a home-
use microwave oven that was first introduced by Tappan in 1955, but these units were still too large and expensive for
general home use. The countertop microwave oven was first introduced in 1967 by the Amana Corporation, which was
acquired in 1965 by Raytheon.
I can finally
cook food
without the
hassle!

3. Spencer was born in Howland, Maine. At the age of just 18 months old, Spencer’s father died and his mother soon left him
to his aunt and uncle. His uncle then died when Spencer was just seven years old. Spencer subsequently left grammar
school to earn money to support him and his aunt. At the age of 12, he began working from sunup to sundown at a spool
mill, which he continued to do until he was 16 years old.

4. At this time, he heard of a local paper mill that was going to begin using electricity. Spencer was from a very remote
community in Maine, where people knew very little about electricity. He was so intrigued that he began learning all he could.
He applied for this work at the paper mill, and was one of three people who were hired to install electricity in the
plant, despite having never received any formal training in electrical engineering nor even finishing grammar school.

5. By 1939 Spencer became one of the world’s leading experts in radar tube design. Spencer was now working at Raytheon, a
contractor for the United States Department of Defense, as the chief of the power tube division. Largely due to his
reputation and expertise, Spencer managed to help Raytheon win a government contract to develop and produce combat
radar equipment for M.I.T.’s Radiation Laboratory. This was of huge importance to the Allies and became the military’s
second highest priority project during WWII, behind the Manhattan Project.

6. At that time, magnetrons were used to generate the microwave radio signals that are the core mechanism of radar, and
they were being made at the rate of 17 per day at Raytheon. Spencer developed a more efficient way to manufacture
them, by punching out and soldering together magnetron parts, rather than using machined parts. His improvements were
among those that increased magnetron production to 2,600 per day. For his work he was awarded the Distinguished Public
Service Award by the U.S. Navy.
It sure is! Excellent
work! Here’s this for
your efforts!

7. One day while building magnetrons, Spencer was standing in front of an active radar set when he noticed the candy bar he
had in his pocket had melted. Spencer was not the first to notice this issue, but he was the first to investigate it. He
decided to experiment using food, including popcorn kernels, which became the world’s first microwaved popcorn. In
another experiment, an egg was placed in a tea kettle, and the magnetron was placed directly above it. The result was the
egg exploding in the face of one of his co-workers, who was looking in the kettle to observe.

8. Spencer then created the first true microwave oven by attaching a high density electromagnetic field generator to an
enclosed metal box. The magnetron emitted microwaves into the metal box blocking any escape, allowing for controlled and
safe experimentation. He then placed various food items in the box, while observing effects and monitoring temperatures.

9. Raytheon filed a patent on October 8, 1945 for a microwave cooking oven, eventually named the Radarange. In 1947 the
first commercially produced microwave oven was about 6 feet tall, weighed about 750 lbs., and cost between $2,000 and
$3,000. In 1967 the first relatively affordable ($495) and reasonably sized (counter-top) microwave oven was available for
sale.

10. The microwave oven today is now a simple household item used commonly in homes across the world. Microwave ovens
now, unlike the 1900s, come in varying sizes, shapes, textures, intensities, and styles. There are dozens of companies that
produce microwave ovens daily; but they all respect the true inventor, Percy Spencer.

11. THE END