The Accidental Invention of Microwave Ovens

Microwaves are the tiny, speedy cousin of our beloved ovens. And like all the best things in life, the invention of the microwave was a complete and utter accident.

Even more than that, it was invented by a man with no qualifications, who had left grammar school at the age of seven!

Percy Spencer could have worked his entire life at the spool mill where he was hired from the ages of twelve to sixteen. After losing family at a young age, he didn’t have good chances, but while working he heard that the local newspaper mill was beginning to use electricity – and he was fascinated. He learned everything he could about electricity, eventually securing himself a job as one of three people qualified to install electricity in the mill.

microwave4At the age of eighteen he signed up to the US Navy, largely due to an interest in wireless communications and how they had worked on the Titanic. In his spare time and on watch he consumed books about radio technology, metallurgy, chemistry, physics and more, so by the time he was thirty five he was one of the leading experts in the world on radar tube design.

In his position as head of the power tube division in Raytheon, he managed to secure them an exclusive government contract, the goal being to create new radar equipment for MIT. After The Manhattan Project, this was America’s biggest project to aid the allies in World War II.

One day when Spencer was building magnetrons to generate microwave signals for radar, he noticed that the chocolate bar in his pocket had melted, and although other scientists had noticed the same thing he was the first to look into it by seeing which other foods had the same effect. Popcorn kernels were the first (so Spencer is to thank for microwave popcorn!) and then an egg, which exploded in the face of one of his colleagues. He soon perfected the design into what we would now consider a microwave oven by attaching a high density electromagnetic field generator to an enclosed metal box and shooting electromagnetic waves into the box from a magnetron. The waves were confined within the box, creating a safe work environment and a controlled method of experimentation.

Raytheon patented the Radarange, which would later become known as a microwave, in 1945 and in 1947 one of these pieces of kit would cost $5000, weigh 750 pounds and stand at a massive six feet tall. It wasn’t until twenty years later that microwaves became moderately affordable ($495) and a size that could actually fit into a kitchen!

speedyweenyFun fact: In 1947, Spencer introduced the microwave oven to the public in the form of a hot dog cooker named the Speedy Weeny!

Percy Spencer, meanwhile, went on to earn a Distinguished Public Service Award for the sensitive radars which, when attached to bombers, were able to detect the periscopes of German U-boats, changing the game of warfare forever. This is the highest award for a civilian to be granted by the US Navy.

As well as being perfect for heating up a late-night frozen burrito, microwaves have revolutionised many of the foods we enjoy today. Microwave ovens can be used to dry out potato chips, defrost meats, roast coffee beans and peanuts, and even make oysters easier to shuck. Outside of the food industry they’re used to dry pencils, flowers, match heads, ceramics, paper and leather – they truly are a gift to mankind.

Percy Spencer, we salute you!


And remember kids…never put metal in the science oven!