50 years of the mi­crowave oven

CityPress - - Voices -

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. 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. 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 TALK TO US

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