Guest Post: The home microwave oven turns 50

by Timothy J. Jorgensen, Georgetown University

The year 2017 marks the 50th anniversary of the home microwave oven. The ovens 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 miniaturization and cost reductions in manufacturing made the ovens small enough and cheap enough (a still steep US$495; US$3,575 in 2017 dollars) for use in the kitchens of the American middle class. Now, it would be hard to find a U.S. home without a microwave.

It will be quick and it will be hot.
1967 promotional image for the Amana Radarange

Amana, a subsidiary of Raytheon corporation, actually called their 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 prior to World War II, 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 in their path.

By measuring the bounced-back radio waves, distant objects or objects hidden from view by clouds or fog 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 actually utilized to track the movement of rainstorms across the landscape, and the age of modern radar-based weather forecasting began.

Original cavity magnetron as used to develop radar.
Mrjohncummings, CC BY-SA

At the heart of radar technology is the “magnetron,” the device that produces the radio waves. During World War II, the American military couldn’t get enough magnetrons to satisfy their radar needs. So Percy Spencer, an engineer at Raytheon, was tasked with ramping up magnetron production. He soon redesigned the magnetron so that its components could be punched out from sheet metal – like sugar 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 candy bar 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 corn 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.

Amana Radarange commercial from 1976.

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,” or even just “microwaves.” 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 centimeters); so they are considered “micro” (Latin for small), as far as radio waves go.

Microwaves are able to heat food but not the paper plate holding it because the frequency of the microwaves is set such that they specifically agitate water molecules, causing them to vibrate rapidly. It is this vibration that causes the heat production. No water, no heat. So objects that don’t contain water, like a paper plate or ceramic dish, are not heated by microwaves. All the heating takes place in the food itself, not its container.

Microwaves have never completely replaced conventional ovens, despite their rapid speed of cooking, nor will they ever. Fast heating is not useful for certain types of cooking like bread-baking, where slow heating is required for the yeast to make the dough rise; and a microwaved steak is no taste match for a broiled one. Nevertheless, as the fast-paced American lifestyle becomes increasingly dependent upon processed foods, reheating is sometimes the only “cooking” that’s required to make a meal. Microwave ovens’ uniform and rapid heating make them ideal for this purpose.

Over the years, there have been many myths associated with microwave cooking. But the truth is that, no, 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 cooking with a microwave oven or eating microwaved food. In fact, the leakage standards for modern microwave ovens are so stringent that your candy bar is safe from melting, even if you tape it to the outside of the oven’s door.

What’s the deal with metal in the microwave?

Nevertheless, you should be careful about microwaving food in plastic containers, because 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. But if you want to mark the date with an anniversary cake, best not to cook it in your microwave – you’d likely end up with just a very hot and unappetizing bowl of sweet mush.

Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University

This article was originally published on The Conversation. Read the original article.

Guest Post: What would you have eaten for Christmas in medieval times?

by Iona McCleery, University of Leeds

With Christmas almost upon us, there will be plenty of frenzied present shopping and meal planning. Haven’t made that Christmas cake yet? Fear not. If you were preparing the festive meal 600 years ago you’d have far more on your plate.

The picture below is a calendar page from a Book of Hours, a type of prayer book popular among pious rich people in the Middle Ages. Apart from the costumes they are wearing, the people at the bottom of the page seem much like us – keeping warm and enjoying their food and drink.

The 12th Day of Christmas

It may surprise you to learn that this particular calendar month is January. The feast day celebrated by the couple is Epiphany on January 6, picked out in red (Epyphania). Our Christmases, hectic though they may be, are actually a doddle compared to the traditions of old. Medieval people celebrated all 12 days of Christmas, from December 25 through to Epiphany – the day the three kings turned up with gifts for the newborn Jesus – although they did not usually feast every day. Some households had their big feast on Christmas Day. For others it was the first of January or the 6th, depending on local custom.

Wealthy or poor

There’s not much detail as to what the couple ate at their winter feast. The artist was more interested in depicting the strawberries and flowers in the margins than in putting food on the table. This is typical of medieval manuscript art. Even elaborate descriptions of royal feasts say little about food. We know even less about what the poor ate, although lords probably feasted their tenants at least once over Christmas.

We do know that preparations for winter would have begun in the late autumn. Humans and animals both ate the same basic foodstuff: grain. Poorer people did not have enough grain for animals over winter so most pigs and cattle were fattened up on acorns and slaughtered. Calendars commemorate this strategic act for the months of November and December as in the images below, paired with the relevant signs of the zodiac (Sagittarius and Capricorn).

Fattening in November and slaughtering in December.
Courtesy of the Brotherton Library, University of Leeds

Of course, the wealthy could continue to keep their animals alive, so they had fresh meat all winter. It’s not true that they used spices to liven up rotten meat: cloves, nutmeg, cinnamon and pepper were imported from India or Indonesia, so if you could afford them you could afford good meat. The rich could also afford sugar – candied fruit, sugared almonds and sweets have always been popular Christmas treats.

The poor would have eaten sausage and bacon instead, salted fish if they could get it, stored or dried apples, peas and beans, perhaps a bit of honey, and would only have had the added flavours of onion, leeks and garlic. Even salt was expensive. The hungriest time was actually not the months that we associate with winter cold, but the months of April and May. It was then that stores had run out and there would be little growing yet in the garden. Nor was there much dairy as hens naturally lay less in winter and cows don’t produce milk until after they have their spring calves.

Yuletide feasting

The best way to find out what the wealthy ate is to turn to their financial accounts and cookery books. Cookery books such as the Forme of Cury, written for the household of King Richard II (1377-1399), provide some tasty recipes. For a recent project we made recipes from this text and others for the public to try at festivals and markets around Yorkshire. In Castleford Market in December 2012 we prepared seasonal tastes such as gingerbread, mutton stew (mounchelet) and apple pudding (pommesmoile).

An opulent Christmas feast.
Courtesy of the Brotherton Library, University of Leeds

But it was nigh on impossible to prepare the main dishes that the rich had at their feasts. Turkey originally came from the Americas so was not found on English tables until the late 16th century. It probably replaced a showier but much less tasty bird: the peacock. The price of these birds meant that most people had to be content with another large expensive bird, the goose, which was a traditional Christmas main course until relatively recently. Also closely associated with Christmas was the wild boar – a boar’s head was often brought into the hall to accompanying carols. But it wasn’t always intended for eating.

And then elaborate displays of prepared meat, sugar or wax in the form of fantasy animals, angels and castles were often part of the entertainment, sometimes even moving mechanically or exploding.

So count yourself lucky as somebody who won’t go hungry this winter. You may have left the pudding quite late but you can leave the peacock and pommesmoile for next year.



Iona McCleery, Lecturer in Medieval History, University of Leeds

This article was originally published on The Conversation. Read the original article.