Step 4: Curing the Clay
If you do a lot of polymer clay, having a dedicated toaster oven is a great idea or else your home oven will need to be cleaned frequently because it will pick up the odors of the clay. Also, most ovens are off by as much as 100 degrees, especially toaster ovens, so investing in a cheap in-oven thermometer would be a good idea as well.
Clay needs to be cured at the right temperature and time for a few reasons. If it is cooked at too low of a temperature (or not long enough time) the inside of the piece could be raw. If clay is left raw on the inside, it will slowly begin to degrade the cooked clay on the outside and within a few month to a year your piece will be gummy and ruined. If your oven is too hot (or you cook it too long) you can burn the piece and cause caustic fumes and a burned and brittle piece.
Placing your piece on a piece of aluminum foil make it easy to take out of the oven. I also use a fan to blow the air out of a window because the fumes can give you a bit of a headache- especially if you burn it.