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About Baking Polymer Clay

Baking polymer clay? - You can do it at home:
Polymer clay contains plasticizers in order to make it soft and malleable. It is therefor necessary to cure it to get it hard. Baking polymer clay burns of the plasticizers and hardens the clay so it becomes strong.

One (among many) reasons to why polymer clay has become so popular, is that you don't need an expensive kiln to cure it. You can do it at home in your own kitchen stove. Now, people do not always agree on that, since there have been some controversy about toxic fumes when baking, and whether they are harmful or not.

You can read more about that here and make up your own mind. But do not worry, there are steps you can take, to eliminate both fumes and residue in your oven, when you are baking polymer clay. I will cover that a little later. Let's first get into the baking of polymer clay, and how to do it right – for the clays sake.

Temperature when baking:
The different polymer clay brands vary slightly on baking temperatures. You will find the temperature printed on your clay packs, both in Celsius and Fahrenheit. If you like to mix clays, always bake the beads at the lowest suggested temperature, and prolong the baking time instead. This in order to fully cure the clay that needs higher temperature.

Unfortunately kitchen ovens are not always correct when temperature is involved, therefore it is recommended that you use an oven thermometer when you are baking polymer clay. You can buy these in a hardware store, or online from Polymer clay suppliers. Test your stove before you bake clay in it, and regulate the temperature accordingly when curing polymer clay. Some polymer clay artists leave the thermometer in the oven while they cure the clay, to constantly tune the right temperature, as it may vary slightly during the baking process.

If you by accident burn the clay, it will cause toxic fumes that are harmful. The best thing to do in that case, is to turn of the stove, carry the piece outside to cool of, and air out your stove and kitchen thoroughly.

Baking polymer clay at a too low temperature, can leave parts of it uncured. After some time – up to a year or so later, this will ruin your beads, as the uncured clay will eat away on the rest of the bead, causing it to crumble. Therefore read the label on the pack carefully. Always use the temperature suggested as right temperature must be reached to achieve maximum strength.

If you don't want to use your kitchen stove when baking polymer clay, there are ovens specially made for baking clay. It is not recommended to cure clay in a toaster oven, as it is very small inside, and the clay therefore comes to close to the heating elements.

And DO NOT use a microwave oven. It may be tempting to do so, but the labels on the clay packs strictly states that microwave must not be used to bake polymer clay.

Curing time:
Baking time depends on how thick the clay is. It is usually set for 30 minutes per 1/4” or 1/2” thickness. This means that if you shall bake something big or thick, the baking time must be prolonged accordingly. Now, here is the good part about baking polymer clay: It can't be over-baked.

Polymer clay can be cured for hours without getting burned, if the recommended temperature is used. You can also re-bake it over and over, without harming it. So if you worry about under-curing when you are baking polymer clay, leave the beads in the oven for a longer time. The longer the better, actually, as it will only strengthen the beads.

What to bake polymer clay on:
This depends a little on what you want to cure. I put flat pieces on a ceramic tile when I am baking polymer clay, but you can also use glass, a silicone baking sheet or a sheet of cardboard. To avoid shiny flecks, place a sheet of paper under the beads while curing. You can also dust them with cornstarch, as that prevents them from sticking to the tile.

If the flat pieces bend upwards a little after curing, put a piece of paper and another tile on top of them. Then place something heavy on top of the tile and leave it to cool down.

Some want the shiny surface you get when you place polymer clay on glass or ceramic, and even sandwich flat pieces between two tiles during baking, to get both sides shiny.

Larger pieces needs to rest on something that won't leave flat marks on them. You can use a piece of polyester batting, or you can lay the pieces on a bed of cornstarch or baking soda. The latter can be washed of the beads after baking.

When you make beads, you can make holes in them prior to curing or after. If you make them before, you can bake them on a bamboo skewer , a knitting needle or a mandrel. This prevents that the beads get flat marks, as they hang on the skewer. If it is hard to get them off the skewer after baking, put them back in the oven for a few minutes,and they will come off easy.

An aluminum tray for baking polymer clay

If you want to hole your beads after baking, you can use a piece of polyester batting, or cornstarch as mentioned above or you can accordion-fold a piece of paper, and bake the beads on that. I find that this sometimes leave marks on the beads though, if the beads are a little on the heavy side. So I prefer the polyester batting.

Clays that darken when baked:
Some colors darken when you bake them. Some also change their color a little. Take this into consideration when you mix your colors, so you don't get some unwelcome surprises.

I have a color box where I have samples of all the colors and color mixes I use. I can then see what a color looks like when baked. If you want to mix new colors, make small examples first, before you indulge yourself in a big project. If you don't like the way they change when darkening, try to mix a bit of white into the color.

Translucent clay yellows or get brownish if it is baked on a too high temperature. Therefore, when you use translucent clay, use the suggested temperature and bake the piece longer, if you mix it with another clay that need a higher temperature to cure. Some polymer clay artists plunge their beads in ice-cold water right from the oven to enhance the transparency.

Cracked beads:
I guess we all experience that a bead crack during baking. This may be due to several causes, like the type of clay, how well the clay was conditioned, and baking temperature. However, there are some things you can do to prevent it and to fix it.

Some leave their beads inside the oven until it is cool, and say this prevents cracks. My beads usually crack when I have been too lazy to condition the scrap clay core bead well enough.

Conditioning the clay thoroughly is of great importance, since it presses all air out of the clay. Air pocket in the clay causes the bead to crack, as air expands during heating. So condition well. And, needless to say, bake at the right temperature.

When a bead has cracked, you can “heal” it by plunging the bead in icy water, while you press the crack together. This actually works, very well with one crack. If the bead has several cracks, as is the most usual, it is a bit more tricky. You can then try to close one crack, heat the bead up for a few minutes and then heal the next crack. May take a while though. Personally, if a bead has one or two cracks, I “heal” it. If it has several cracks, I trash it.

Using your kitchen stove:
As mentioned earlier, some do not like to bake clay in their kitchen stove, since that is where food is cooked. But what if you can't afford a special clay oven? Ahhh! There is of course a solution to that, thanks to all those fantastic people out there, who share their experiences with us.

Bake in a disposal aluminum pan, and put another on top. Close them with clothes pegs. This keeps the fumes and the smell inside the roasting pans. When baked, leave until cool, before you open the pans.

An aluminum pan with lid, for baking polymer clay

You can also bake them inside a turkey roasting bag, if you do not pierce the bag. The fumes get trapped inside the bag, and you get no fumes or residue inside your oven. Leave to cool before you open it though.

Personally I use the aluminum pans, they are cheap and easy to get hold of. I find that the smell from baking clay is close to non existing if I don't open them until cool. Still though, always have well ventilation in the room when you are baking polymer clay. And, of course, never bake clay and food in the oven at the same time. It is said not to be of any hazard, but it does not cost much to be a little cautious, as we say in Norway.

Well, that's it, folks, happy baking!

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Baking Polymer Clay In Aluminum Tray 
Would you still have to wash out your oven when using the aluminum pan?

How hard is the clay when it is cured? 
Hi, Your article is very interesting but I have a question. I have just 'cooked' my first batch of tiles but they still seem to have some bend in them …

Ice Water Not rated yet
I have read where people routinely dunk their fresh out of the oven baked clay in an ice water bath. I wonder what this accomplishes and what the outcome …

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