Posted on 25 Apr 2015 18:59
Most people set their oven at a certain temperature, say 350, and assume that the inside of the oven will reach exactly 350°F. Then, they assume that the oven will do a perfect job of maintaining this temperature during the cooking process. Quite likely, your oven is not that accurate at all. Many home ovens are off by around 25° and some can be off as much as 50 degrees. If you do a lot of baking, this can be frustrating, causing over-baked or under-baked cakes, cookies, breads, pastries, pies, etc.
Let's say your oven 25 to 50° hotter than its setting. You put a cake in the oven, set your timer, and when it goes off you check your cake. It's burnt on the outside! Then you find out it's not even fully cooked in the center. That is what too high a temperature will do. In fact, oven temperatures that are too high or too low can cause many problems with cakes, even when you do everything else correctly. Uneven rising, cracks, crumbly texture, sticking, and cakes that are too dense or heavy can all be related to inaccurate temperature (although not exclusively).
Don't worry, though. Testing and then adjusting your oven is a simple matter and you can soon have it heating up to the temperature you need.
Before we get to that though, keep in mind that your oven will likely beep or do something else to tell you when it has reached the target temperature, that is when it is "pre-heated." This may take, say, 10 minutes. However, it is best to wait another 20 to 25 minutes past this time, as this time is needed for the heat in the oven to even out. Some cooks wait as long as half an hour.
Test Your Oven with an Oven Thermometer
It is quite easy to test your oven for temperature. First, you need an oven thermometer. Many oven thermometers are inaccurate themselves. The most reliable kind is probably an old-fashioned stick thermometer which is alcohol (not mercury) based, such as the one I linked above.
To start your oven test, place your oven rack in the center position, and then place the thermometer in the middle of the rack. Don't place it along the edges, as the temperature is hotter there, due to the hot oven walls. You'll be cooking the middle of the rack, so place your thermometer in the middle.
Set your oven to 350° (you can use another temp but this is an easy one to work with). Let the oven pre-heat, and then give it another 20 minutes or so to make sure it is at its final temperature (for the current setting). Check the reading on the oven thermometer to see if it reads 350°, or something higher or lower like 325° or 375°.
If it is 25 or more degrees lower, you can add 25 to your target temperature and set the oven to that every time you use it. So, if you find your oven is too low by 25 but you want it to be 350, set it to 375. Do the opposite for an oven that reaches too low a temperature. You may not be able to be completely accurate, so just get as close as you can.
You can leave most oven thermometers in the oven all the time, although some will not be able to withstand very high temperatures, and they may get dirty, causing them to become unreadable. Also, they will likely get in the way. Although you may wish to check your oven temperature every time you use it, you should be able to just check it once a month, or thereabouts, then adjust your oven settings as needed. Then, you can keep your oven thermometer in a drawer until needed.
Calibrating Your Oven
Ovens must be calibrated to perform perfectly. If you have an oven with digital temperature controls, it may allow you to calibrate the settings very easily. Check the owner's manual for your oven. Usually, it is just a matter of holding down a bake or temp button until the calibration setting appears, and then pressing "up" or "down" to add or remove degrees of temperature. Each press of the up or down will will add or remove one degree. After checking your oven with an oven thermometer, as explained above, simply add or subtract the proper number of degrees. Initially, the calibration should be set to zero, unless you have calibrated it previously, after which it will display a positive or negative number. After you have added or subtracted the right number of degrees using the calibration function, your oven will automatically adjust and you can then use it normally.
You will still want to periodically check your oven with a thermometer to see if anything has changed, as you may need to re-calibrate.
If you have an older oven, without digital control buttons, there will probably not be a way to easily calibrate it yourself. Theoretically, you should be able to get it serviced, and recalibrated so that it reaches and maintains the correct temperature. Due to the inconvenience and expense of such services, it is highly unlikely that most home cooks will want to do this, especially for an older oven. And when you find out that even a brand new oven can be off, you will probably question the wisdom of spending money on service! It is almost certain that a re-adjusted oven (if it can be adjusted) will just end up off-temp again in a while.
If you can't calibrate your oven, then just adjust your temperature settings up or down based on the instructions given above, and you should be fine. You are simply 'calibrating' your oven manually, as you go. Check the temp periodically, and as long as it isn't broke, don't fix it!
What if Calibrating Your Oven Doesn't Work?
If you calibrate your oven and it still fails to heat to the proper temperature, it may be that the temperature sensor is not working. This is also a fairly easy thing to replace in most ovens, and even novices can do it. There are many home DIY websites where you may be able to find information on replacing a faulty oven temperature sensor. You can also test the sensor before you assume it's broken, but this will require purchasing an ohm meter. Not every problem that may occur is an easy fix, however.
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