How to Bake Polymer Clay: Part 2 – Temperature

Today I’m discussing baking temperature and why it’s so important for getting good results with your polymer clay projects. When baking polymer clay, temperature is everything! This article is second in a series on Baking Polymer Clay.  Part 1 of this series discussed choosing the right oven for baking or curing your polymer clay projects. Part 3 will be giving specific tips and tricks about baking polymer clay. And Part 4 we’ll talk all about how long to bake polymer clay.

What temperature should you bake polymer clay?

  • All ovens lie, so get a thermometer to verify what the actual temperature is. Adjust the dial to get the correct temperature.
  • For a good cure with polymer clay, temperature is important!
  • If your clay is burning, your oven is too hot. Period.
  • Most polymer clay is far more heat tolerant than you’d expect. It will not instantly burn at 1° above the recommended setting.
  • Polymer clay does not burn and turn black unless the oven is near 350°F (190°C).
  • If you reduce the temperature out of fear of burning, you will underbake your project, which causes your project to break.
  • Different clay brands have different recommended temperatures. In most cases, aim for the temperature on the label.
  • Most ovens have terrible temperature control, so baking is the most likely culprit if you have breakage or browning.
  • Make sure to read the articles on polymer clay Ovens, Tips and Tricks, and Baking Time.

Breakage is nearly always caused by underbaking. One of the most important things you can do to ensure good results is to invest in an oven thermometer (Affiliate Link – learn more here). They’re not expensive and can typically be found at most discount or kitchen stores for less than $10. Every oven is different and many will operate at a temperature much different than you set. Some ovens are too hot and others are too cool. Even more take a long time to get up to the correct baking temperature, even once the oven’s “preheated” light has come on. It’s always best to check.

Get to know your oven, watch what its pattern is. Does it get to the correct temperature quickly? Does it hold the temperature or does it cycle wildly?  This is such an important factor that some professionals even recommend getting two thermometers just in case one of them is wrong!

Need baking help?

Learn about the right temperature, times ovens, and baking setups to ensure optimal results. No more broken or scorched projects!

Underbaking Polymer Clay

Underbaked polymer clay will break easily. Underbaked translucent polymer clay isn’t as clear or translucent as it should be. It is extremely important to bake your polymer clay projects no lower than the recommended temperature for at least the correct length of time.

Sometimes people underbake their polymer clay because they fear burning or scorching their clay. Put your mind at ease. As stated on the Polyform website, both Sculpey and Premo do not break down and burn until the temperature reaches 350°F (177°C). The same is true for Kato Polyclay (as per personal communication with Connor Bizon, a chemist with Van Aken International.) Assuming your oven functions properly and you set the correct temperature, you are far more likely to underbake than burn your clay.

Overbaking Polymer Clay

Scorching and burning polymer clay is pretty nasty. Just think of what any burned plastic smells like! Burned polymer clay does release small amounts of irritating and caustic hydrogen chloride gas.  If you burn your clay, turn off the oven, open the windows, and leave the area until it clears out. Just like when you burn your pork roast. But aside from airing out the area and throwing away the burned mess, you won’t need to undertake any “toxic waste cleanup” or decontamination of the area. Though the room and your oven may smell bad for a while (no different from when you burn popcorn in the microwave…yuck!)

But you’re not going to burn your polymer clay unless you set the wrong temperature on your oven, your oven malfunctions, or your piece is too close to the element. It’s easy to accidentally set the wrong temperature, though. I’ve caught myself doing it several times for the simple reason that Premo bakes at 275°F but most of us bake a casserole at 375°F. So double-check and don’t let your “autopilot” take over!  Another thing that happens is there will be clay cooling in the oven when another person comes along and turns the oven on to preheat for making food. Next thing you know, your creations are up in smoke!

Browning or Darkening of Polymer Clay

Even if your oven doesn’t burn clay, it can still cause discoloration much in the same way that bread turns brown when placed next to the heating element (toast!). Translucent and lighter colored clays are very susceptible to this. I’ll discuss some ways to prevent this and protect your artwork in part three of this series. But remember that reducing your oven’s temperature (as verified by a separate oven thermometer — Affiliate Link – learn more here) is not the solution. You will just end up with underbaked, weak projects.

Learn how to prevent overbaked and darkened translucent polymer clay. The Blue Bottle Tree.
I was so upset when these gorgeous translucent mokume gane beads came out of the oven yellowed and darkened. This experience made me look for why this happened and find out how to prevent it in the future.

Times and Temperatures for the Best Results

Polymer clay manufacturers clearly state the recommended temperatures at which their products should be baked. Some brands warn you not to exceed certain temperature ranges. This is quite understandable because manufacturers have to write instructions for ALL types of consumers. And most ovens are wildly inaccurate. So they have to give instructions that give a balance between adequate curing and the very real and frustrating reality that many ovens will be too hot and could cause the clay to burn. The instructions on the package are what is going to give adequate results for most consumers.

But it’s also common knowledge among professional polymer clay artists (who collectively bake a lot of clay) that the strongest results come when polymer clay is baked for longer than the manufacturers recommend. I agree with this wholeheartedly. For example, the instructions on packages of Kato Polyclay tell you to bake at 300­°F (150°C) for a mere 10 minutes. When I tried that, the clay was grossly underbaked and easily crumbled in my fingers. The same sized pieces of Kato Polyclay baked 30 minutes came out strong and impossible for me to break. Baking polymer clay for longer than recommended will not harm it in the same way baking a loaf of bread too long will give you a hard brown brick. Light colored clays might darken and discolor, but they will not burn. Even if you leave your clay in the oven all day long, as long as you don’t exceed the correct temperature, it will not burn.

What Temperature Should I Bake Mixed Clays At?

Sometimes, especially if you’re making something from scrap clay, you will have a project that contains a blend of more than one brand of polymer clay. What temperature should that project be baked at? I’ve never seen an official answer from any polymer clay manufacturer, so I can only speak from my own experience. I always bake at the highest temperature needed of all the brands in the mix. The same sized pieces of Kato Polyclay (which cures at 300­°F (150°C)) with Fimo (which cures at 230°F (110°C)), I will use the higher temperature. I’ve yet to have any trouble with this method.

An exception would be if you are baking, for instance, the body of a cat figurine out of Kato and the ears out of Fimo. I’d bake the body at the higher temperature to assure a full cure and then apply the ears and do a second baking at the lower temperature.

The next article in this series, Part 3, is full of tips and tricks about baking polymer clay. I’ll show my baking setup and give lots of information about finding solutions to baking problems.

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70 thoughts on “How to Bake Polymer Clay: Part 2 – Temperature”

  1. Hi! I love your blog and and have recently gotten into jewelry making during the pandemic. Unfortunately, sometimes my Premo pieces some out hard after baking and when I try to bend them, they break in half. Do you think this could be underbaking or overbaking? I’ve used an oven thermometer and bake around 275/280 for about 90 minutes just to be safe.

    1. If the clay is snapping, it is UNDERbaked. Not overbaked. If you’re baking that long and they’re still snapping, then your oven is not hot enough or you have them so well insulated that the heat is not penetrating. Are you using a tile sandwich?

      1. Oh wow, thanks! I hadn’t considered that despite the time and temp they could STILL be underbaked. I just place a tile in a tin foil baking pan, put parchment paper on top, then the clay pieces. Then, I put another baking pan upside down on top of it and use binder clips to hold the “lid” in place. I think I got that from you 🙂

        1. It depends totally on the oven. For a long time, the biggest complaints from newbies were burning and color change. In a super hot oven, more protection gives better results. I think that ovens lately are running cooler, meaning that this strategy gives more protection than necessary. Problem is, it’s hard to know how an oven will behave until it “proves itself”.

          1. Thanks so much! I’ll just have to keep testing … and try not to cry when beautiful pieces fail the flex test. 🙂

  2. Am I right or wrong to extrapolate from this article that if I can cure a mix of Premo and Kato at the higher temp temp that Kato requires, I might (test test and test again) have a potential oven tolerance upper limit of +25F for straight Premo?

    1. My official word is to follow package directions for temperature, of course. 🙂 But if you’d like to experiment, you have more options. There are a lot of variables. But yes, you can sometimes cure Premo at 300F. Actually, you can cure all polymer clay well over 300F….BUT….the clay will discolor. So if you’re using a dark color where it won’t matter, a higher temp is perfectly fine. It will not burn. Clay will not burn…I mean actually turn black and bubble and smoke…until it reaches close to 350F. (If you are having black/bubbling at lower temps, your oven is lying…it’s really hot in there.)

  3. Hi! I found an old package of what I’m pretty sure is Polymer clay. I don’t have the packaging anymore so I have absolutely no idea how long or what temperature to bake it. Any advice?

  4. I’m very new to clay, I think I need a thermometer. I’m baking at 150c for Kato, but it’s bubbling and smoking a bit. I bought a small toaster oven to use. If I use the home oven, are there any requirements for cooking food in the oven after? Thanks

    1. Nope, just make sure you’ve set the temp to the correct number when you switch back and forth from food to clay. It’s all too easy to forget and both clay and food don’t fare so well when baked at the wrong temp. If Kato is bubbling, your oven is way off. So yes a thermometer is definitely in order.

      1. Hi there! I’ve been trying to use liquid sculpey to help secure the posts on my earrings…unfortunately, they darken in color after second time baking and no longer match the other components of the earrings. Any advice on how to remedy this? Thank you!

  5. Hi ,

    Just wondering about baking times with the bake and bond and fimo . I’m looking to sandwich my earring post between two bits of clay instead of glueing after. I’m unsure what temp to bake this at as the bake and bond and fimo both have different temperatures

    Thanks for your help

    Rosie x

    1. Just use the temperature that’s appropriate for the Fimo. And btw, that should be 265°F/130°C. Fimo’s label does state 230/110, but if you’ll read the fine print, it also lists the higher temp. Use that. 🙂

  6. Hi

    I use premo to bake my items. The top of the flat tiles are usually nice and have a nice finish. However the bottom of my tile is usually a different colour (more matte) than the top. In addition, there are some spots that are of a different colour.

    I use tiles and put a layer of baking paper. May i know what i am doing wrongly?

    1. I’m sorry, I don’t understand how it could be more matte. Usually, When you bake something on a shiny tile, there will be shiny spots on the bottom side They might look slightly darker, but they’re not in reality. They’re just glossy. To prevent this, just make sure the item is sitting on paper. In other words, put paper between the item and the tile. Then bake it. You won’t have those odd shiny spots anymore.

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