When we set our oven to pre-heat we wait for the beep and know the oven is ready. The light shows us as well right? But as soon as we open the door the light changes telling us the temperature has dropped. But what if the oven isn’t hot enough to start with? What is the oven is too hot to start with? How do I know that the number shown or the dial is set just right? If you are like me you say “just go get a thermometer”, it’s not that easy. Manufactures may take care in making the product but the shippers, store workers, and we customers don’t. This means the thermometer could be wrong as well. Using sugar we can check to see how our oven is heating.
I have looked many places on the internet and have found that Sucrose (table sugar) melts at 367°F / 186°C. The sugar turns from a powdered, granulated substance to something resembling glass. Later as the temperature reaches 375°F/190°C it melts and caramelizes, which is the breakdown of the molecules of sucrose.
Pour a spoonful of sugar into an oven-safe dish that you can see into or on a cookie sheet lined with foil, set the to 350°F / 177°C. Even after an hour, it should still be powder or granules. It might turn slightly brown due to decomposition, but it shouldn’t melt. If it does, your oven is too hot. Next, turn your oven up to 375°F / 190°C. The sugar should completely melt within 15 minutes or so. If it doesn’t, your oven is calibrated too cold. Check to see if your oven has either an adjustment knob or a calibration offset setting; otherwise, just keep in mind the offset when setting the temperature. Note that your oven will cycle a bit above and below the target temperature: the oven will overshoot its target temperature, then turn off, cool down, turn back on, etc. It’s possible that your oven could be “correctly” calibrated but still melt the sugar when set to 350°F / 177°C due to this overshooting, but it would have to overshoot by about 15°F / 8°C.