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Early Kelvinator Home Microwave

Kelvinator Microwave “Radarange” thought to be the first home microwave oven used in Eau Claire, Wisconsin, 1956.
(Museum object #1985.30)

By today’s standards, this microwave oven is quite bulky and very heavy. Housed in a brushed stainless steel cabinet which measures 27” high by 24” wide by 25” deep, the unit weighs nearly 170 lbs! In 1956, Dr. Herbert Grewe of Eau Claire purchased this microwave, previously used as a demonstration model, from the Northern States Power Company. The list price was $1200 but Grewe paid only $900 – still a significant expenditure for the time (as a comparison, the very best double-oven Kenmore range available in the 1956 Sears catalog cost only $359). Dr. Grewe believed it to be the first home microwave used in Eau Claire, and used it in his home until 1978 at which time he gave it to the Chippewa Valley Museum. In 1985 CVM transferred the microwave to the Wisconsin Historical Society.

Pleased with the convenience of his microwave, Dr. Grewe became an enthusiastic supporter. While on a ski trip to Utah in 1958, he espoused the virtues of his microwave to a gentleman whose friend happened to be a sales manager for the Raytheon Manufacturing Company, the originator of the microwave. Grewe wanted to obtain an operator’s manual, so he wrote the sales manager. Expressing his satisfaction, Grewe stated, “The unit is terrific... We use the Radarange everyday for something.” Grewe continued to use this microwave for another 20 years until one of the vacuum tubes finally burnt out in 1978.

Raytheon, of Waltham, Massachusetts, produced all of the electronic components and sold them to companies to build and sell the actual oven unit under their own name. Kelvinator, the Appliance Division of the American Motors Corporation, made this unit. Other early makers included Tappan, Hotpoint, and RCA.

A microwave oven uses microwaves to rapidly cook food. The waves cause water molecules in the food to vibrate, producing heat, which is distributed through the food by induction. An electron tube called a magnetron produces the microwaves. In 1946 Dr. Percy Spencer, a Raytheon engineer, was conducting research related to radar technology and magnetrons when he discovered that the candy bar in his pocket had melted. Intrigued by this, Dr. Spencer placed some popcorn kernels near the tube and observed the popcorn sputtering, cracking, and popping. Soon after, Raytheon patented the first commercial microwave oven in 1947 for use in restaurants and commercial food production. That same year Raytheon introduced a microwave oven unit for the home and called it the “Radarange.”

Advances in electronic and microwave technology have greatly reduced the size and cost of microwaves making them present in nearly every American home today. Like Grewe’s early Kelvinator, most of these are used on a daily basis for food preparation.

[Sources: "Who Invented Microwaves" online at; Correspondence in Museum accession file 1985.30.]


Posted on August 10, 2006

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