I’ve often wondered exactly what was happening in the oven under that tin foil or cornstarch. What exactly is the temperature under there?
The chart above shows what the temperatures were using the following methods. All started with a cold oven and the oven dial set at 270˚F.
- Convection turned off
- Convection turned on
- Ceramic tile tented with aluminum foil
- Covered with cornstarch in an aluminum baking tin
- Two small ceramic tiles inside two aluminum pans with one inverted as a lid. I’ll call this a “baking box.”
Convection off was the most stable and closest to the 270˚ temperature on the dial. It took 10 minutes to warm up and level out.
With convection on, the temperature started high and bounced around about 8˚ hotter than the oven setting. Convection basically turns on a fan that circulates the heat to eliminate hot spots in the oven. I thought convection would make the temperature more stable, but that wasn’t true for my oven.
Tented with aluminum foil started at a high temperature and after 20 minutes had climbed to 35˚ hotter than the oven dial. Wow. It seems like some compensation should be made, such as setting the oven 35˚ lower and preheating it for 20 minutes.
Cornstarch and the baking box started at very low temperatures, rose steeply and leveled out after about 35 minutes at 10-20˚ hotter than the oven dial. Again, maybe compensation should be tested, such as setting the oven 10-20˚ lower and preheating for 35 minutes.
I’m not quite sure what to make of this temperature chart, but it is illuminating. Testing with your own oven is the best way to know what works for you.