50 years of the microwave oven

2017-03-19 06:07

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Timothy J Jorgensen

This year marks the 50th anniversary of the microwave oven, which were first sold for home use by Amana Corporation in 1967, but they had actually been used for commercial food preparation since the 1950s.

It wasn’t until 1967, however, that technology miniaturisation and cost reductions in manufacturing made the ­ovens small enough and cheap enough for use in the kitchens of the American middle class.

Amana, a subsidiary of Raytheon, actually called its first model the Radarange – a contraction of radar and range (as in stove).

What do microwave ovens have to do with radar? Radar is an ­acronym for “radio detection and ranging”.

Developed before World War 2, the technology is based on the principle that radio waves can bounce off the surfaces of large ­objects.

So, if you point a radio wave beam in a certain direction, some of the radio waves will come bouncing back to you if they ­encounter an ­obstruction.

By measuring the bounced-back radio waves, distant objects or ­objects hidden from view can be ­detected.

Radar can detect planes and ships, but, early on, it was also found that rainstorms caused interference with radar detection.

It wasn’t long before the presence of such interference was utilised to track the movement of rainstorms across the landscape, and the age of modern radar-based weather forecasting began.

At the heart of radar technology is the magnetron, the device that produces the radio waves.

The birth of radar technology

During World War 2, the US military couldn’t get enough magnetrons to satisfy its radar needs.

­Percy ­Spencer, an engineer at Raytheon, was tasked with increasing magnetron production.

He soon redesigned the magnetron so that its components could be punched out from sheet metal – as cookies are cut from dough – rather than each part needing to be individually ­machined.

This allowed mass production of magnetrons, raising wartime production from just 17 to 2 600 per day.

One day, while Spencer was working with a live magnetron, he noticed that a chocolate in his pocket had started to melt.

Suspecting that the ­radio waves from the magnetron were the cause, he decided to try an experiment with an egg. He took a raw egg and pointed the radar beam at it. The egg ­exploded from rapid heating.

Another experiment with mielie kernels showed that radio waves could quickly make popcorn. This was a remarkably lucky find.

Raytheon soon filed for a patent on the use of radar technology for cooking, and the Radarange was born.

As time passed and other companies got into the business, the trademarked Radarange gave way to more generic terminology and people started calling them microwave ovens.

Why microwaves? ­Because the radio waves that are used for cooking have relatively short wavelengths.

While the radio waves used for telecommunications can be as long as a football field, the ovens rely on radio waves with wavelengths measured in inches (or centimetres); so they are considered to be “micro” – as far as radio waves go.

Microwaves are able to heat food and not the paper plate holding it because the frequency of the microwaves are set so that they ­specifically agitate water molecules, causing them to vibrate rapidly. This vibration causes the heat production.

No water means no heat.

Microwaves have not completely replaced conventional ovens – ­despite their rapid speed of cooking – nor will they.

Fast heating is not useful for certain types of cooking, such as baking bread, where slow heating is required for the yeast to make the dough rise.

Nevertheless, as our fast-paced lifestyle becomes increasingly dependent ­upon processed foods, reheating is sometimes the only “cooking” that’s required to make a meal.

The ­microwave’s ­uniform and rapid heating system makes it ideal for this purpose.

Myths

Over the years, there have been many myths ­associated with microwave cooking. But, the truth is, they don’t destroy the food’s nutrients.

And, as I ­explain in my book Strange Glow: The Story of ­Radiation, you don’t get cancer from either using a ­microwave oven or eating microwaved food.

In fact, the leakage standards for modern microwave ovens are so stringent that your chocolate is safe from melting, even if you tape it to the outside of the oven’s door.

Nevertheless, you should be careful about microwaving food in plastic containers as some chemicals from the plastic can leach into the food.

And, yes, you shouldn’t put any metal in the microwave ­because metallic objects with pointed edges can interact with the ­microwaves from the magnetron in a way that can cause electrical sparking (arcing) and consequently damage the oven or cause a fire.

The microwave oven has definitely transformed the way most of us cook.

So let’s all celebrate the 50th anniversary of the home microwave and the many hours of kitchen drudgery it has saved us from.

Jorgensen is director of the Health Physics and Radiation Protection Graduate Programme and associate professor of radiation medicine at ­Georgetown University in the US.

This article first appeared in The Conversation

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