Percy Spencer and the Microwave

Renowned American inventor Percy Spencer was born July 19, 1894 in Howland, Maine. When he was only 18 months old his father died and mother abandoned him leaving him to his aunt and uncle. When Spencer was seven years old, his uncle died, forcing him to leave grammar school to get a job to support himself and his aunt. By age 12, Spencer was working sunup to sundown in a spool mill. At age 16, Spencer heard of a local paper mill that was going to begin using electricity, which was a rare new technology in his small remote hometown. The idea of electricity peaked Spencer’s curiosity and encouraged him to learn all he could about the developing technology. Soon after Spencer applied for this work at the paper mill and was one of three people who were hired to install electricity in the plant, even though he never received any formal training in electrical engineering and did not even finish grammar school. It was here that Spencer learned his basic electricity knowledge that he would later use to invent his microwave oven. At the age of 18, Spencer joined the U.S. Navy when he became interested in wireless communications after learning about the wireless operators aboard the Titanic when it sank. While standing watch at night on the navy ship he was assigned to, Spencer read every text book he could get ahold of, subsequently teaching himself trigonometry, calculus, chemistry, physics, and metallurgy.
Right before WWII, Spencer went to work with Raytheon, a contractor for the United States Department of Defense, as the chief of the power tube division. Known in the US Department of Defense for his brilliance, 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. At that time, magnetrons were being used to generate the microwave radio signals that are the center of Radar technology. While working there, Spencer developed a more efficient way to manufacture these microwave radio signals by punching out and soldering together magnetron parts, rather than using machined parts. Over the next few years, Spencer would grow Raytheon from 15 employees to over 5,000 and his improvements increased magnetron production from 17 to 2,600 per day. For his work he was awarded the Distinguished Public Service Award by the U.S. Navy in 1939.
One day while at work, Spencer noticed that the magnetrons he was building had melted a candy bar he had in his pocket. Spencer and his colleges had noticed that heat came off of the active radar sets, but Spencer was the first to investigate farther into their observation. Spencer experimented with this heat by using corn kernels and eggs. After having an egg explode in his face, Spencer attached a high-density electromagnetic field generator to an enclosed metal box, creating the first microwave oven. 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 pounds, and cost between $2,000 and $3,000. In 1947 the public was introduced to this new food-heating box, but it wasn’t until the 1960’s that the microwave would become a countertop kitchen appliance that was affordable and relatively easy to use. By 1975 over one millions microwaves had been sold in the United States alone, causing several companies to join this growing market. Many of these companies were military based due to their familiarity with the magnetron. In 1986 the U.S. Bureau of Labor Statistics reported that roughly 25% of American homes and restaurants had microwaves, increasing to 90% by 1997. It would be safe to say that the percentage has risen since 1997 making the microwave one of the most popular home appliances not only in the Unites States, but internationally as well.

Percy Spencer and his invention:


Old Radaragne microwave:




About caitlineichlin

History major at California State University San Marcos and aspiring high school history teacher.
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