A properly calibrated oven is essential for ensuring consistent cooking results. Because many people don't have an oven thermometer (though we think they should), we developed an easy method to test for accuracy using an instant-read thermometer. Here's how to do it: 1. Set an oven rack to the middle position and heat your oven to 350 degrees for at least 30 minutes.
2. Fill an ovenproof glass 2-cup measure with 1 cup of water. Using an instant-read thermometer, check that the water is exactly 70 degrees, adjusting the temperature with hot or cold water as necessary.
3. Place the cup in the center of the rack and close the oven door.
4. After 15 minutes, remove the cup and insert the instant-read thermometer, making sure to swirl the thermometer around in the water to even out any hot spots. 5. If your oven is properly calibrated, the water should be at 150 degrees (plus or minus 2 degrees). If the water is not at 150 degrees, then your oven is running too hot or too cold and needs to be adjusted accordingly.
We tested this method in multiple ovens, both gas and electric, and all worked well. (Note: To avoid shattering the glass cup, allow the water to cool before pouring it out.)
Where to put your thermometer:
Oven Thermometer Placement Published September 1, 2003. Where’s the best place to put an oven thermometer for the most accurate reading? We put this question to Karen S. Yaggie, a marketing representative at Taylor Precision Products, maker of the oven thermometer that won our test (the Taylor Classic Oven Guide). "The best place to get a reading," Yaggie told us, "is the center--exactly where you place the baking dish for the food that you are preparing." She emphasized that the thermometer should not be positioned within 6 inches of any oven wall or of the oven ceiling, floor, or door. Our tests showed that ovens do indeed have hotter and cooler spots. Tests on a gas range, for instance, showed the temperature differential between the bottom and top of the oven to be close to 50 degrees. We suggest that to get a good reading you place the thermometer at the dead center of the oven—right in the spot where the food will be cooking—as it preheats. When it's time to put the food in the oven, you can move the thermometer to the side or hang it from a rack such that it hovers over the food. If it ends up sitting fewer than 6 inches away from the interior surface of the oven, remove the thermometer until the food is finished cooking. (We also learned from Taylor that it is safe to keep the thermometer in the oven at any time outside of the cleaning cycle.)
From: America's Test Kitchen: http://www.americastestkitchen.com/ibb/posts.aspx?postID=303915&viewreplies=true
NOW, calibrate one of the ovens in the lab following the above directions. After you have completed the calibration, determine what a person should do in order to get the correct temperature on the dial. Put this on the white board for the kitchen groups to be able to follow when they use the oven.