Tuesday, January 05, 2010

Polymer Clay Tips and Tricks:

How to Bake Polymer Clay Items?

One of the most frequently asked questions is how to bake (or cure) polymer clay items. Here are a few tips and tricks to get you started.

To bake your polymer clay (PC) creation, you will need an oven that can be accurately programmed to generate temperatures between 215ºF (102ºC) to 325ºF (163ºC). This range is sufficient to bake any polymer clay creation. I will tell you more about baking temperature requirements for various brands of PC later, but right now let's concentrate on choosing the right oven.

You can use a regular oven, a toaster, a convection oven, or a special oven for polymer clay (the later one is now available in most craft stores in PC section).

It is OK to use a regular oven if you are not baking PC too often or if you have a tall item to bake (a vase, for example). However, if you are going to make a lot of PC items, consider buying a dedicated oven for your polymer clay items.

Polymer clay is rated non-toxic for people; however it smells a little bit even during the normal baking. Some brands of clay (such as Kato) smell stronger than others, and some people are more sensitive to this smell than the others. The walls of your oven adsorb PC fumes, and after baking PC (in your regular oven, for example), you may notice the PC smell next time when you use the oven for something else. That is why it is better to have a dedicated PC oven. Definitely, never bake polymer clay items and food in the same oven at the same time.

Also keep in mind that there are warnings about PC fumes being dangerous to birds. It is also a good idea to limit exposure of small children and pets to PC fumes during baking.

If you are concerned about the smell while baking PC items, consider these suggestions:

- place your oven in a well-ventilated area or in an isolated room;

- cover your PC item with foil or place it between two disposable aluminum pans clipped together;

- after baking, leave your PC item in the oven to cool down, if possible (This does not work for translucent clay, since the finished item has to be immersed into an iced-water bath immediately after baking to enhance the translucency).

As I said earlier, ideally, the oven has to be accurate. This means that when you set it up to a certain temperature, the oven shall produce this particular temperature. In reality, however, most ovens are slightly off. For example, in order to have 300ºF in my oven, I have to set it up to 315ºF. That is why, before using your oven to bake a PC object for the first time, you have to check its actual temperature against the set temperature (and plan to adjust it accordingly, if necessary). Do not trust the built-in thermometer, use a separate one, such as a candy thermometer or a stand-alone oven thermometer. You may also use a special thermometer for PC baking (available in craft stores in PC sections, on the Internet).

Also keep in mind that different sections of the oven usually reach slightly different temperatures during baking. The middle section is usually the best place. Spots close to the heating elements get hotter, while those close to the front door, are usually colder than the middle section. Plan to use the middle part of the oven for baking your PC items, and place your stand-alone thermometer in this part of your oven as well.

To properly check the oven temperature, first wait until the oven indicates that it has reached the set temperature. At this point, you may read your stand-alone thermometer and compare it to the oven setting. Leave the thermometer in the oven and read it a few more times over the next 30 minutes to check for any temperature spikes. If the fluctuations are too wide, you need to find another oven. If the average temperature differs from the set temperature, by a few degrees, simply adjust it as needed.

Now let's talk about the temperature and duration of baking.

Different brands of polymer clay require different temperatures for baking. Also, some brands have changed their formulations over time, resulting in changes to their recommended baking temperature. Luckily, there is an easy way to find out the baking temperature: it is printed on every polymer clay package. Always keep your polymer clay packaging and check it before setting up your oven.

Here are a few examples of the recommended baking temperatures for different brands (the purpose of this table is to demonstrate the importance of verifying the baking temperature for every package of clay, and not to give you a complete and accurate reference):

Baking temperature is 230ºF for the new Fimo, and 265ºF for an old version of this brand;

- 215ºF to 270ºF for Cernit,

- 275ºF for Premo, Sculpey, Pardo, and old Kato,

- 285ºF for Bake & Blend,

- 300ºF for new Kato.

It is better to avoid combining different brands of clay until you are comfortable with baking. Later on, you may actually want to combine two or more different types of clay with different baking temperatures in your creation. In this case, bake the mixture at the lowest temperature required for its components.

Recommended minimum baking time is 30 minutes per 1/4” of thickness at the appropriate temperature. You may bake a 1/4” thick piece longer if you wish, but keep in mind that, for some brands, light colors may darken with prolonged baking. The thicker your PC piece, the longer you will need to bake it (for example, a set of round beads 1/2” in diameter will require about 60 minutes of baking). Always calculate your baking time based on the thickest part of your creation. Keep in mind that a complex sculpted piece may be baked a few times in between the sculpting sessions, if necessary.

The last question I wanted to address is what to bake your PC items on.

For flat objects, use glass or ceramic tiles. To prevent thin flat sheets of PC from warping during the baking process, sandwich them between two ceramic tiles and keep them in this position not only during baking, but also while the PC is cooling down after baking.

Shiny spots may develop on the surface of your PC items coming in contact with ceramic tiles during baking. If you want to avoid this, cover your tile with a sheet of paper.

Dimensional pieces (such as round beads or small sculptures) may be baked on polyester stuffing or batting, on a pile of cornstarch or baking soda, or on various holders made out of cardboard, paper towels, crumpled aluminum foil, and other materials. Keep in mind that PC softens up a little bit during baking, so any protruding parts have to be secured and propped during this process.

In a nut shell:

- know your oven,

- always set it up carefully,

- read the temperature instructions on the PC package to figure out the optimal baking temperature,

- measure the thickness of your items to calculate the minimal baking time,

- use proper materials to position your PC item on during the baking process.

Happy baking!

1 comment:

luthien said...

thank you so much for taking the time to write this out. it is indeed very informative.

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