Ever questing for "the perfect microwave oven," engineers constantly add new features and refinements. The most important development to date is the introduction of variable power levels that give you as much control and flexibility as conventional ranges.
If, for example, a sauce should bubble furiously on HIGH (100% power) and threaten to overflow its container, you need only reduce the power level to MEDIUM-HIGH (70%). Or if a stew should drop below a simmer on MEDIUM (50% power), you need only raise the power level to 60% or 70%.
Two things determine the different power levels: whether the microwaves cycle on and off and how long they remain "on" per cycle.
On HIGH there is no interruption in the flow of microwave energy. On MEDIUM the microwaves pulse on and off at regular intervals, so that periods of rest (no power) alternate equally with those of full power.
At lower power levels, the "off" periods outlast the "on" and at higher power levels, it's the reverse. These on/off cycles mean that foods as heat-sensitive as meats, eggs, cheese and creams can cook far more evenly because the heat inside them has a chance to spread slowly and equalize during each "off" period.
Top-of-the-line microwave ovens offer 10 variable power levels, the simplest ovens only HIGH and "Defrost" (usually 30% power), but it varies from manufacturer to manufacturer.
Older ovens may also label 70% power as MEDIUM and 40% power as LOW, so it may be necessary to test the microwave oven to determine just what its power levels are.
1. Mix 1 cup cold water and eight ice cubes in 1-quart measure. Stir exactly 1 minute.
2. Pour 1 cup cooled water into microwave-safe 1-cup measure. Discard remaining water and ice cubes.
3. Microwave water, uncovered, on HIGH (100% power) until it comes to full rolling boil, 3 to 4 minutes. Jot down exact time it takes in microwave oven. Discard water and let measure come to room temperature.
4. Repeat steps 1 and 2. Microwave water, uncovered, on MEDIUM (50% power) until it comes to full boil. Again jot down time it takes. If it takes water exactly twice as long to boil on MEDIUM as it does on HIGH, then the MEDIUM power level on microwave oven is indeed 50% power. If the water boils in less than twice the time, the MEDIUM power setting is higher than 50%.
5. Again repeat steps 1, 2 and 3, but use power setting lower than MEDIUM. Once you determine which setting on the oven actually represents 50% power, you can then calculate which settings correspond to LOW, MEDIUM-LOW and MEDIUM-HIGH. Make record of each and post as handy reference.
Please note that power levels can fluctuate according to local electricity consumption, thus at times of peak usage, the microwave oven may not be operating at full capacity.