I understand it’s common, but the dial on my oven doesn’t match the actual temperature inside the oven.
About a year ago, when I bought my new oven and oven thermometer, I tested the temperature once for each setting in the range I needed. I wanted to be sure there weren’t temperature spikes and to learn what the temperature actually was. The results seemed a bit random, but I wrote them down and proceeded to bake clay.
I should have looked into it further because I ran into quite a few problems with clay breaking and yellowing.
This time, got more scientific. I recorded the actual temperature of my empty oven every five minutes for seven different oven settings. It showed me a few things I didn’t know.
1. When my oven beeps to say it’s reached the temperature set on the dial, it lies. It seems to beep after 4 minutes regardless of what temperature it’s reached. It actually takes it an additional 10-15 minutes to reach temperature.
2. My oven runs about 5˚ cool. When I set it for 300˚ for Kato clay, I’m actually only getting 295˚. That doesn’t seem like a big deal, but 10˚ can make all the difference in whether clay breaks or not, so it’s probably better to set it one notch hotter.
3. My oven starts to cool off before the time is up. This may be common. I don’t know.
There are many ovens and oven thermometers available. I use a small Breville oven set on bricks. It has quartz healing elements and it gradually warms up and maintains a stable temperature. It has a fairly large baking space. It has button you can push for convection, which basically turns on a fan to circulate heat.
When I first tested convection, the temperature spiked, so I’ve avoided using it. One thing I don’t like is it has only 10˚ increments on the dial, rather than 5˚, for the lower temperature range needed for polymer clay.
The oven thermometer I’ve used for the longest is a Polder digital oven thermometer. It’s meant for measuring the temperature of food up to 392˚, not an empty oven. I fried it using high temperatures and had to replace it.
I just bought two other regular oven thermometers, a Rubbermaid and a Cooper-Atkins. All three thermometers show different temperatures. Aaarrgh. The Rubbermaid is almost the same as the oven dial. The Polder is about 5˚ lower and the Cooper-Atkins is 13˚-15˚ lower than the dial. The Cooper-Atkins was recommended by Cooks Illustrated, so I thought it would be the best. It’s hard to know what to do, so for now I’m using the Polder.
P.S. I bought all these products myself and received nothing from the manufacturers.