In other articles I’ve given a lot of suggestions for creative things to do with polymer clay. But there are a few things you shouldn’t try.
1. Use the clay right out of the package, without conditioning it. Clay must be conditioned – kneaded or run through a pasta machine, several times – before it’s formed into an object and cured. If it isn’t conditioned the finished object will be very prone to falling apart.
There’s only one possible exception to this rule, and that’s if you’re using tiny particles of new clay but are mixing them with conditioned solid clay or liquid clay. In this case, the latter will act as a binder for the new clay, and the piece may hold together after curing.
2. Store uncured clay in the sun or in a hot room. Doing this is a really good way to cure your clay before you’ve done anything with it. And once clay is cured there’s no way to undo the process. You can still use the piece in something else, but you’ll have to use it “as is.”
3. Process clay with an appliance that you also use for food. Polymer clay is certified non-toxic, but that’s assuming that it isn’t eaten. It contains plasticizer and other substances that are almost impossible to completely clean from a piece of machinery. If you’re using something for clay, do not – I repeat, do not – use it also for food.
Here I’m mainly talking about pasta machines, food processors, and other clay mixing and shaping tools. But there’s also been some debate over whether it’s safe to cure clay objects in the same oven you use for cooking and baking. The objects should be sitting on or in a tray, of course – a tray that’s “dedicated” for polymer clay use – so the clay shouldn’t come in contact with any part of the oven. But the curing process does burn off the plasticizer and may leave a slight residue on the interior of the oven.
Some people believe that cleaning the oven after each curing is enough to make it acceptable for normal cooking and baking. But this can be a lot of trouble. Most people who work with polymer clay end up buying another oven and using it just for clay. This doesn’t have to be expensive. After starting out curing clay in a regular oven (and having no trouble with it, except for the electricity bills) I went to a local thrift store and got a good quality used toaster oven. Then I verified with an oven thermometer (that cost more than the oven did) that the temperature was correct and consistent, and I’ve used this oven successfully ever since.
4. Curing clay objects at a temperature much higher – or lower – than that recommended on the package. Using too low a temperature will cause the object to cure incompletely, which will make it fragile and more prone to lose its shape. Using too high a temperature could be dangerous; the clay will emit fumes that may be hazardous to breathe and will need to be cleared out of the room. Remember – just like many other things, polymer clay is non-toxic when used as directed.
5. Curing clay objects in a microwave oven. If you’ve ever listened to a microwave when it’s “cooking” you may have noticed a periodic change in sound. That’s the heating going on and off. This process may work great for food, but it’s unsafe for clay, and could spell disaster – for both people nearby (think “fumes”) and the oven. Clay items have been known to blow up in microwaves.
And a bonus tip, this time from a positive standpoint – if you’ve been working with clay, always wash your hands before handling food. Even if your hands look clean, they’ll have plasticizer on them from the clay. Wash them thoroughly (see this article for tips on how to do that) before preparing food or eating.
Polymer clay is such an incredibly creative art medium that it’s a shame to have to say anything negative about it. But like most craft and art supplies it has its uses and its limitations. If you keep the limitations in mind you’ll be better able to safely take advantage of its many creative possibilities.