Microwaves are generated by a device called a magnetron. The magnetron sends microwaves through a metal tube called a wave guide. Microwaves tend to bounce off metal, so they pass along this tube into the oven chamber.
There are two ways of handling the microwaves once they reach the end of the wave guide. One is called distributed energy. A little fan like propeller, called a stirrer, is placed at the entrance to the oven chamber. The stirrer scatters the microwaves around the inside of the oven. They ricochet around, bouncing off the inside metal lining of the oven and the special glass in the oven door until they hit something that contains moisture and will absorb them.
- A distributed energy stream produces even penetration from aU directions. That’s one reason why a cook shouldn’t use a metal pan in a microwave oven. The microwaves coming up from the bottom of the oven chamber will bounce off the pan, so food will only be heated from the top and maybe the sides, depending on the pan’s height. Proponents of distributed energy point to that random pattern as a plus, since all sides of the food are penetrated by the microwaves. However, even in the best design, there are some hot or cold spots.
- Another reason for not using metal utensils or foil in a microwave oven is the danger of arcing. Your prospect may ask about the use of metal. Check the manufacturer’s specifications. If arcing is listed as a problem with a specific oven model, it could result in damage to the magnetron and void the oven’s warranty. In a microwave oven with uneven distribution of energy, the bulk of the waves focus in the center of the oven. Proponents of this concept claim the concentration of waves cooks the food faster than the distributed method, since that center area is the hardest to heat. There are still waves ricocheting off the bottom and walls of the oven, but most are concentrated in the center of the oven. If speedy reheating of larger items or plates full of food is the purpose of the oven, uneven distribution offers best results.
How Oven Controls
The decision between several models of equal power and cavity size usually comes down to the controls. These can range from simple turn-to-set rotary dial timers to user-programmable controls.
The biggest benefit of programmable controls is that they use push buttons which can be programmed for the proper cooking or reheating time of a specific food.
In some top-of-the-line models, programming is more sophisticated. One manufacturer provides controls that turn on a power setting for a specified time, then change to another setting for a second period. That’s useful for thawing a frozen pre-cooked cut of meat, then reheating it evenly for serving.
But, even with the most sophisticated controls, a kitchen worker can punch the wrong button and have everything go wrong. Some operators opt for a rotary timer, then mark the face of the oven around the timer with the position for specific foods, getting the same effect for minimum cost.
High Standards of Setting
The microwave oven is probably the most protected-and inspected-appliance in the kitchen. Each oven must meet standards set by the Federal Communications Commission, Occupational Safety and Health Administration, the Underwriters Laboratory and the National Sanitation Foundation. Most of these seek to ensure that there is no danger of workers being exposed to microwaves or electrical shock.
Interlocks have been designed to cut off the energy before the door is opened even slightly. The glass in the oven door is coated with an iron compound that works like a piece of metal to bounce all the waves back into the oven cavity. As further insurance, some manufacturers use a perforated metal screen in the window opening.
In addition to all of the regulations that affect the manufacture of a microwave oven are those of a growing number of state or local health agencies. These require periodic testing of commercial microwave ovens for possible microwave leakage. Now, just choose your suitable size of microwave for yourself immediately!