Accidental Inventions


The Microwave Oven

The microwave oven was recently rated as the #1 technology in making people's lives better - ahead of the answering machine and the atm.

The first consumer model, the Amana Radarange, was introduced in 1967 and cost $495 - equivalent to $3000 today - and sparked a revolution in American lifestyle. Once thought of as a gimmick, they are now found in 90% of all homes. And it all started with a bar of melted chocolate.

Fun Facts
  • Percy Spencer obtained over 225 patents in his lifetime.
  • Percy's formal education ended at the 6th grade.
  • The Titanic's fuel requirement was 825 tons of coal per day.
  • Raytheon supplied over 80% of the magnetrons used during World War II.
  • The original RadarRange required plumbing because it was water-cooled.
  • The first commercially available microwave contained both conventional and microwave heating elements.
  • In 1976, the microwave oven became a more commonly owned kitchen appliance than the dishwasher, reaching nearly 60%, or about 52 million U.S. households.

Percy Spencer, Inventory

Percy Spencer was born in the rural town of Howland, Maine in 1894. His father died when he was 18 months old and his mother left shortly thereafter. Percy moved to live with an aunt and uncle in south Lincoln, Maine.

When Spencer was 5, a Lombard log hauler broke down in front of their house. Unique for being the first vehicle to use a caterpillar track, it was essentially a steam locomotive without a track. Percy spent many a day exploring the hulking machine as his uncle Henry worked to fix it. They would enjoy riding in the engineer's cab together until Henry passed away when Spencer was 7.

Percy was now head of the family. He dropped out of school and began work at a machine shop in Dexter, Maine where he became a skilled machinist. When the shop was converting to electrical power, a 16-year old Spencer, with no prior training, signed up as one of three men to outfit the factory with the new source of power. Through trial and error, Spencer emerged a competent electrician.

Inspired by the heroism of the wireless operators during the sinking of the titanic in 1912, Spencer joined the navy to learn wireless telegraphy. Lacking much of a formal education, Percy taught himself what he needed to know while standing watch late at night.


After the war, Percy Spencer became the 5th employee of the growing Raytheon company in Lexington, Massachusetts.

There, he was exposed to some of the brightest minds in physics at nearby M.I.T.

Spencer proved to be an invaluable asset to Raytheon as he began work on photoelectric vacuum tubes.

Throughout World War II, the power tube division at Raytheon expanded from 15 employees to over 5,000. This was due largely to Spencer's intense work ethic. For seven years he worked every single day of the week, including holidays.

This legendary drive coupled with Spencer's ingenuity was mainly responsible for Raytheon landing a major combat radar construction contract.


During the battle of Britain, the United States military obtained a model of a microwave magnetron from the English. The magnetron was the power tube of the radar sets and increased the radar's sensitivity tremendously.

The British hoped Raytheon could mass produce the magnetron. Upon U.S. entrance into world war II, fifteen of Spencer's radar sets, called "maggies", were installed into U.S. bombers. The new radar sets were sensitive enough to spot the periscope on German U-Boats. However, it took a master machinist an entire week to bore the tube out of a solid piece of copper with tolerances of less than ten thousandths of an inch.

Squeezing every bit of efficiency out of the Raytheon factory's machinery and manpower, Spencer was only able to increase production to 100 a day. The RAF needed thousands to fight off the Luftwaffe.

A stack of coins in Spencer's pocket provided the answer. Instead of creating the magnetron from a solid piece of copper, Percy devised a way to create it out of thin cross-sections stamped out by a machine that any semi-skilled worker could operate. Slices of copper alternated with slices of silver-solder were stacked on top of each other and fused together in an oven. To further increase efficiency, he designed an ingenious conveyor-belt oven.

This was the advantage that the RAF needed to slow the German onslaught. Production sky-rocketed from 100 to over 2,600 magnetrons a day. For this and other achievements, Spencer was awarded the highest honor a civilian can receive from the navy, the distinguished public service award.


Shortly after the end of the war, Spencer was touring one of the laboratories at Raytheon. Pausing momentarily in front of a magnetron, he felt a strange sensation and noticed the candy bar in his pocket beginning to melt. Although other scientists had noticed this phenomenon, they all ignored it. Percy, however, quickly sent for a bag of popcorn. Holding it up to the magnetron, they popped within minutes.

Spencer continued his experiments with the magnetron and a few eggs. When a curious co-worker stuck his face too close to the machine, he wound up with a face full of splattered egg. Raytheon knew they had a hit on their hands and began producing the first commercial microwave ovens in 1946.

Resembling a refrigerator more than a modern microwave, the first model stood over five feet tall and weighed over 750 pounds. A consumer version wasn't available to American homes until 1967 when Raytheon acquired Amana and introduced the first Radarange with a massive marketing campaign. Introduced in Chicago, the world's first microwave oven featured 115-watts of power and retailed for $495.

The microwave was such a revolutionary technological step that Amana sent home economists to install the new appliance and cook families' first microwaved meal. These economists were available 24-hours a day for the next year. Today, there are microwaves in 90% of all homes and the most powerful offer over 1,000 watts of power as well as a host of computerized cooking and timing functions.