Even with more than thirty years (sigh) of experience in the matter, I still learn about polymer clay every day. I do not claim to know everything on the topic, but I’ve learnt some things for sure. And learning can be very painful with polymer clay, but the lessons are well remembered!
In this article, I would like to share my personal experience with baking polymer clay, to help you save time if you are just starting out, or give you a new perspective if you are an seasoned clayer and feel stuck.
Baking is a step that may seem secondary but it is crucial for a good polymerization (solidification) of the polymer clay. It is too important a step to be left to chance. Unfortunately that happens too often.
I am so sad when I see people still don’t know how to bake correctly their beloved polymer clay artworks. Your art is important and deserves a long life, so here are a few rules to follow to get perfect results safely.
Every artist has their own recipe so I invite you to experiment and find what works best for you, as long as it is with common sense and respecting safety basics.
CHOOSING AN OVEN
First, bake your artworks in a suitable oven. An electric oven is more precise than a gas oven, and a microwave oven is no use for polymer clay and can even be dangerous.
The ideal is to have an oven dedicated to baking polymer clay, out of respect for your artworks, but also for your food and your health and safety reasons.
Before you buy an oven, ask yourself what you are going to use it for. A miniature oven is perfect for jewelry but limits the size of your artworks if you make sculptures.
You can start with a small oven and invest in a larger one later if your works get bigger. The prices of ovens vary, but to give you an idea, a mini oven costs around 60 EUR while larger ovens cost up to a few hundred euros. An oven lasts years so it is worth the investment. I have had my mini oven for fifteen years and it still works perfectly, but now that I am making almost only sculptures, I wish I had bought a bigger one.
• Baking time varies according to the brand and the size of the works.
• I bake my larger artworks for about 50 minutes and smaller artworks 15 to 20 minutes.
• Preheat the oven until the desired temperature is reached, then place the artworks in the oven.
• If you prefer to put the artworks in a cold oven, don't forget to add the temperature rise time to the baking time (if the objects have to bake 30 minutes and your oven reaches the desired temperature in 15 minutes, objects must remain 45 minutes in the oven).
• Put a timer if your oven does not have one.
• Baking must be long enough for the heat to reach the core of the object.
• If the clay does not bake long enough (or the temperature is too low), the polymerization will be incomplete and the clay will be fragile and more and more brittle over time.
NUMBER OF BAKINGS
You can bake polymer clay several times. It can be useful if you make complex works.
Intermediate bakings can be shorter, but the final baking must be long enough for the polymerization to be complete.
Be careful if you have to handle prebaked parts because they remain fragile despite their appearance of baked clay.
The baking temperature is a huge subject of debate. Below is my personal opinion, I trust your common sense and I will take no responsibility if you start a fire.
Polymer clay requires a precise baking temperature. When baked at a too low temperature, polymer clay remains fragile. Bad news: you can’t see it. Good news: you can cure it again. Overbaked, the clay burns, darkens and blisters; your artwork goes to the trash.
So, why is it so difficult to bake polymer clay?
First, manufacturers know most people will not use an oven thermometer and their baking will be approximate. That is why they recommend an average temperature. It avoids burning the clay in most ovens, but is not the temperature that gives the best results.
Now please do take a seat: most oven thermostats are unreliable, with differences between real temperature and thermostat temperature up to 40°C. All the ovens I have used so far have the same problem, to varying degrees.
Let’s take an example. Staedtler, the manufacturer of Fimo, recommends a temperature of 110°C (a few years ago, it was 125° C so if you own old packages of polymer clay they may indicate that temperature instead).
• An overheating oven, let’s call it A, is set to 110°C. Actually it will heat to 130°C and the artworks will be baked (if you are lucky, because it could be an A+ oven and heat at 150° C and burn all your beautiful work)
• An under heating oven, B, is set to 110°C. Actually it will heat to 90°C, and the artworks will not be fully baked (and you’ll never know until your artwork breaks).
Our problem here is, without a thermometer, you have no way of knowing if you have an A oven or a B oven (or if you are lucky enough to possess a rare model of C oven, the legendary oven that heats exactly at the requested temperature. Some say it never existed, but I still have faith).
THE IMPORTANCE OF USING AN OVEN THERMOMETER
As seen above, oven thermostats are unreliable, which is why it is essential to use an oven thermometer (if you are already a thermometer worshipper, you can skip this part).
An oven thermometer will show you exactly what temperature your oven is and you will avoid unpleasant surprises. It costs around 10€ and will serve years, so it is money well spent.
(Your new best friend, the oven thermometer.)
Since I got my oven thermometer, I have never burnt a batch of works, because I know exactly what is going on in my oven (B type).
I bake my artworks (which mix different brands: mainly Fimo, Premo and Sculpey) at around 125°C and never exceed 130°C. In order to reach this temperature, I set the thermostat to 150°C. The difference between thermostat and real temperature is not a problem anymore, thanks to my thermometer.
When I was a child, all the things I made were fragile and brittle. When I finally bought an oven thermometer, I tested my parents’ oven and found out that the real temperature was 30 degrees under the thermostat temperature. No wonder everything broke so easily back then...
TESTING YOUR OVEN
So, if you’re beginning with polymer clay, have had problems baking it, or just bought a brand new oven, before your first (or your next) baking, I strongly advise you to test your oven. This may prevent a possible disaster.
Heat the empty oven with an oven thermometer for 20 minutes and monitor the temperature regularly. This will show you the difference between the temperature indicated by the thermostat and the actual temperature.
Tip: If the temperature of your oven is unstable, you can leave a ceramic tile for better inertia.
FIND THE PERFECT TEMPERATURE FOR YOUR POLYMER ARTWORKS
To find the temperature that suits best your favourite polymer clay brand(s), make samples: bake separately small and thin squares of clay of the same color and thickness for 15 minutes.
Bake the first sample at the temperature recommended by the manufacturer, then increase the temperature in steps of 5°C, until you see that you’ve almost reached the burning point.
Write the temperature you used on each sample (directly on it, so there is no risk of confusion). Once the samples have cooled, try to fold and break them. The hardest one will indicate the temperature that works best for you.
ARRANGING OBJECTS IN THE OVEN
• Bake items with a flat base on a ceramic tile. A blank ceramic tile is an essential tool: you can work on it, and then put it directly in the oven with your artwork on it.
• Hang small curved objects like beads or put them on a rod to prevent them from rolling (or flattening at the point of contact with the baking support).
• Place large curved objects delicately in a dish filled with baking soda (because the crystals are finer than with washing soda) and well wedged in the baking soda.
• Place your artworks in the center of the oven for better heat distribution, and avoid contact with a heating element. You can bake several objects at the same time as long as they do not touch, otherwise they will stick together.
CHANGE IN APPEARANCE
Polymer clay becomes more matte after baking, and its color darkens slightly. To keep the colors bright, add a little white and mix well.
If you notice a yellowing of lighter clays, it indicates the baking temperature is too high.
VENTILATION AND SECURITY
Pay attention to each stage of baking: burning plastic is bad for your health and for the environment.
Whether you share your oven with someone else or not, check the thermostat before each baking and always check the thermometer before putting your works in the oven.
Open the window when you bake something. A light plastic smell is normal (that’s why you need to ventilate).
If you smell burning plastic, stop the oven immediately, open it, ventilate the room thoroughly, and leave the room until the smoke has dissipated.
Baked polymer clay achieves its final hardness only when it has cooled down.
When the baking is over, stop the oven and be patient: let your artworks inside the oven until they cool down to room temperature. This will prevent you from burning yourself and damaging your works that are still hot and soft.
I hope this article will be useful and can’t wait to see the beautiful artworks you will create, from now on perfectly baked!
I’ve tried to be as complete as possible, but if you have anything to add or if you disagree about something, you are more than welcome to leave a comment!