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 give specific tips and tricks about baking 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 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 leads to breakage.
  • Different brands have different recommended temperatures. In most cases, aim for the temperature on the label.
  • Most ovens have terrible temperature control, so baking is your 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.

People often contact me for help when they’re having trouble getting good results with their polymer clay. And after some investigation, I almost always find that the problems are caused by baking polymer clay projects at an incorrect temperature.  One of the most important things you can do to ensure good results is to invest in an oven thermometer. They’re not expensive and can typically be found at most discount or kitchen stores for between $5 and $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!

Article about using the optimal temperature to bake polymer clay, without underbaking or burning your projects. By The Blue Bottle Tree.

Underbaking Polymer Clay

Underbaked polymer clay can be soft, crumbly, it will break easily. Underbaked translucent polymer clay isn’t as clear or translucent as it should be. And when you underbake a large item, uncured clay at the center will cause the whole piece to be weak. It is extremely important to bake your polymer clay projects no lower than the recommended temperature for at least the correct length of time. In fact, baking your piece even longer will make your piece even stronger.

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 does happen. And I’ve heard that it’s pretty nasty when it happens. 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!

As I described earlier in this series, toaster ovens are notorious for having vast temperature fluctuations that can lead to “toasting” your polyclay projects. Many people opt to use a toaster oven out of fear that using their home oven is somehow dangerous. It’s my personal opinion that many toaster ovens are more likely to be dangerous because of these overbaking issues. I’ve read lots of sad stories of burned clay and I wonder how many of those cases would have been avoided if a full-sized oven were used. I think sometimes people try to avoid a possible or mythical problem but that then leads to a situation with a much higher likelihood of encountering problems.

A lot of people are happy with their toaster ovens, but if you’re one of those who is getting burned clay projects, try using your home oven, with a separate oven thermometer, and see if you have better results.

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) 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 much 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. So if I mix 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 never had any trouble with this yet.

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. Check back to get the next installment or check on my Facebook page for the link.  I’d like it if you’d join the mailing list, too. That way you’ll be sure to get an email when I make a new post.

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

  1. Hello! I’m having trouble with me beads cracking. Temp is set to 130°, 30 mins. Could it be because I was fan forced? Thanks

    1. There are many, many reasons for cracking and sometimes we never know the cause. But that is the bare minimum that you should be baking your beads. I would try baking longer and see if that helps.

  2. I have done three thick pieces and the first one turned brown the second crumbled and now the third turned brown even the blue scarf.was brown.i had the oven at 275 and baked it for an hour.i am new and using a polymer clay oven with ceramic tile in it and have an oven thermometer in it.what am I doing wrong.

  3. Hi Ginger,
    We are making polymer pieces to go into a snowglobe, I want to make a small “present,” and am thinking of wrapping clay around a square of styrofoam, rather than having a solid thick piece. I haven’t used styrofoam in this way before and am wondering if it would work. Do you have any thoughts about this? Thanks.

    1. Styrofoam doesn’t perform well in the oven. It will either shrink or expand (depending on the kind of styrofoam) and in either case won’t support the piece you’re making. Instead, make a core from compressed aluminum foil.

  4. I don’t have an issue with my clay burning. I have an issue with I‎t MELTING. set my pieces in at the recommended temperature for the recommended time. Opened the oven to check on them and they were a puddle of melted clay at the bottom of my oven.

    1. Hi Jamie, polymer clay cannot melt in the oven. It will only harden. What you were using was not polymer clay. Most likely it was plasticine modelling clay. This is a common problem, actually, because the modelling clay is in the same section of the craft store as the oven-bake polymer clay and it can be very easy to grab the modelling clay, assuming it’s polymer clay. If you’ll look at the label, you’ll find that it does not give baking instructions. I’m sorry your hard work got ruined!

  5. Hi there.

    I’m just a bit confused by baking thickness etc. I have made a little cupcake charm with Premo sculpey which is about 22mm high and about 18mm at the widest point across the cake part on the top. I wanted to check which measurement to use to determine baking time. So I should go with the fact it is 22mm in height? Or that the cake part is 18mm wide? If I went with the larger measurement to be sure? So would that mean 22mm /6mm: 3.6, so 3.6 x 30 minutes baking time? Which I get 108 minutes, so approximately that.
    Would that be right?
    Also I am interested in making very small food miniatures but they are tiny and I’ve baked a couple of thin bits and pieces for 10 minutes but they’ve just snapped afterwards. How long do you think for very tiny pieces? Because using the 30 mins per 6mm guideline, well if they’re only 2mm thick then they shouldn’t need more than 10 minutes.
    Hope you can help! Love this website.

    1. It does not need to be this precise. You want to bake long enough and hot enough to allow complete fusion of the polymer clay mass. Larger pieces need longer for the heat to get through them. But baking longer (as long as the temp is correct) will not cause any problems. So it does not need to be precise. It just needs to be ‘enough’. Ten minutes is not long enough for thin bits, so the formula doesn’t work like that. The 30 minutes for 1/4″ rule is just a general guideline. Keep in mind that the temperature goes down when you open the oven door, and it takes time for the temperature to come back up. Some ovens do that quickly, some don’t. So we usually bake tiny things for 30 minutes and large things for 45 minutes or an hour or even longer. If something is going to be thicker than 1/2″, I usually pre-bake a base or use a compressed foil core (like an armature) so I’m not making anything that thick in one baking. Thick pieces run the risk of cracking.

  6. is extremely overbaked clay still usable? my husband makes sculpey replicas of people’s cars, and he accidentally cooked a vw bus at 350 for 2 1/2 hrs before we realized the mistake. it’s a large piece, about 5 inches thick, and I’m afraid that the middle might not be cured even though it is burned on the outside. just wondering if it can be saved, as it really can’t be duplicated.

    1. As long as it didn’t burst into flames and smell like smoke, it will be just fine. It will be dark, of course, but you can paint it. It is cured inside, don’t worry. It was plenty hot enough for that. In the future, however, don’t make things so thick. Make a core from compressed foil, and add clay in stages, baking as you go. You can bake a piece repeatedly. But baking more than 1/4-1/2″ thick at a time can lead to cracking.

  7. Hello Ms. Ginger,

    I am a faithful follower of your articles. You are THE BEST! One quick question – if you are making a project that requires multiple baking sets of many different layers, how long should you bake each layer? And do you run the risk of burning the clay that was baked first by re-baking it each time you add a layer? Does my question make sense? I’m making a lotus flower that works better if I bake each layer of leaves before adding the next layer.

    1. Yes, it makes perfect sense. First, you never will burn polymer clay unless the temperature gets higher than 350°F. You can have some colors darken, but there will be no burning, even if you bake it for days. Bake each layer the length of time that it should take to cure thoroughly. So if you’ve put a 1/4″ layer onto previously baked clay, you will would take it 30 minutes. You may even want to do a final bake for longer so the whole thing gets a long, thorough baking. There is some disagreement about partially baking clay. Some people say that it will ultimately be strong if the final bake is long enough. Others say that partial baking will never be as strong, even if fully baked later. I’ve not tested to be sure. But I can say that I’ve always been happier when I’ve opted to bake longer than when I bake shorter periods of time.

    1. Bake your clay at whatever temperature gives you maxiumum strength and minimum browning. Generally, the longer and hotter the bake, the stronger the clay will be. The optimal temperature for you will be determined by your particular oven, the size of pieces you are baking, the temperature in the room, the reliability of the electrical supply, and yes, the elevation. I recommend making some strips of Premo, getting an oven thermometer, and seeing what the best baking conditions are for you.

  8. Brittany Applegate

    I love your tips! They’re easy to understand and easy to follow along with.

    I just have one question, though. Does the project need to be hollow or can it be solid clay? Because I know some clay projects will explode. (My ceramics teacher in high school always reminded us to hollow out the project so that the hot air/heat can circulate and bake it from the inside too. And if we didn’t hollow it, the heat could cause it to explode).

    I was just curious if Polymer Clay was the same way since it’s being baked under strong temperatures. I’ve never used it before, and I do pretty big projects so this question has always bothered me.

    1. Polymer clay does not need to be hollowed out, and in fact, hollow shapes will need to have an air hole or they can collapse due to the vacuum that is created when the heated piece cools after baking. You are right in your instincts, though, that it’s probably not a good deal to bake a super thick piece. It’s best to use an armature or create a base out of compressed aluminum foil and build your piece on that. Clay is far more expensive than foil, so you’ll definitely want to do this. Try to keep your clay layer less than 1/4-1/2″ thick. You can also bake clay in layers, putting raw clay onto a previously baked base, building it up to the thickness you want. The other problem with baking thick pieces is that cracking can happen when the core is still raw and expanding (slightly), but the outside is baked hard.

  9. I’m so happy to see that you’re still replying to questions on this post! I’m very new to working with polymer clay, using Premo Sculpy, which says to bake at 275°.
    I’m having a problem with my oven not staying at a consistent temperature. It has a digital temperature control, and I bought a new oven thermometer.

    If I set the oven at 275, the temp will mostly hold steady at 250 with occasional bumps to 275 when the elements cycle on.
    If I set the oven to 300, it constantly fluctuates between 275-300, as the elements cycle.

    I worry that the first will cause it to not cure fully, but with the second I’m concerned about scorching or possibly burning? I’d appreciate any suggestions, thank you!

    1. This is the reality that most of us live with. Ovens fluctuate like crazy. What you have to do is set the oven to a temp that it spends as much time at 275 as possible, but protect the clay so that it doesn’t darken if the oven does get too hot. 300 really won’t bother your clay if you have it covered. Also, keep a ceramic tile in your oven to help hold the heat more stable as the oven fluctuates, and make sure it’s fully preheated and hopefully more stable before putting your items inside. When you do, don’t leave the door open for any longer that you have to. Good luck!

  10. I am so glad to come upon this article. I have not baked my beads yet so what do you cover them with to bake them, foil?
    Also, what colors did you use to make those beautiful beads pictured in this article?

    1. Yes, use foil to cover them. Or an inverted aluminum pan. Or even cardboard. There is more info in the rest of my baking articles linked in the article above. I made those beads using a layered mokume gane technique with translucent clay and layers of metallic acrylic paint.

  11. I’m making macaroon cookies out of Fimo polymer clay. This is my first time using polymer clay, and I have a question. The “cookie” is actually 5 layers of clay. 2 layers of “cookie” with a layer of white “filling” inside. This makes the whole cookie (which will be a Christmas tree ornament) about 1 1/4″ thick. 1. When baked, will the layers of clay “bake” together into one piece? 2. Or … should I be baking each layer separately, then glue them together into one finished cookie after the pieces are baked? If I do that, each layer is about 1/4 thick. So that would drastically reduce my baking time (rather than baking one piece that is 1 1/4″ thick. What would you advise?

  12. Thanks so much for your article!

    I’m pretty new to polymer clay, hoping to open an Etsy shop soon. I’ve done two bakes so far in my home oven–and accidentally set my second one to 425F…Needless to say some of my pieces were very discolored. I’m thinking that my oven may have been inaccurate, because none of them seemed particularly burned, just discolored. Some of them came out unscathed. Are these all right? Or brittle? I wouldn’t want to put out any jewelry that is flawed, however heartbreaking that loss of time and energy may be.

    Also, as a college student, still living at home, do you suggest getting a separate toaster oven to bake my projects? This baking thing seems very finicky, especially if you have a wonky oven. I feel like my second attempt at baking freaked my family out a bit, it was very smelly and just a bad experience.

    I’ve been baking on a cookie sheet with foil. Would it help if I covered my pieces with foil overtop as well? Also, I’ve heard that baking twice can make my pieces stronger, so if I had some tentacle pendants, baked them, and then put on the suckers, and baked it again, would that be a good idea?

    Many of my pieces have taken a lot of time to make and after reading some of your articles, I’m very nervous about ruining my clay. There’s so many variables and there is so much I have to learn! I’m used to ceramic clay. And I have so many questions, some I don’t even know how to ask! I have a feeling I’ll be around a lot…

    1. First off, please don’t be nervous about baking your clay. Make sure that the temperature inside your oven is correct, then bake according to label directions or a bit longer if you feel it needs to be stronger. Yes, your oven is going to be inaccurate. Most of them are. You need to take some time, do some test bakes, and learn how your oven behaves. Overbaked clay will be discolored, underbaked clay will be brittle. Find a setup that gives the results you want and then reproduce that.

      1. My oven is one of those rare ones that are accurate.Yep, I actually got away with not using an oven thermometer and my creations came out fine!

  13. Pingback: Curing Polymer Clay What to Use | Serenity Clay

  14. I’m trying my first polymer clay experiment tomorrow right after I run out and buy two metal pans and an oven thermometer. I have the tile already and the clips. I’ve made a flattened glass bead that I intend to incorporate into my piece. Cross your fingers and wish me luck. Thanks for your very informative articles. Betsy

  15. Deborah Thacker

    Thank you so much for the article. I thought your makume gane beads were gorgeous. They are like a happy accident. 🙂

  16. I’ve been working with polymer clay for a few years now, but I’ve never covered it before. My pieces have all come out fine. What is the reason for covering it?

    1. To protect against the color shift that can happen with some colors. I didn’t do it in the beginning, but after I had a whole batch of translucent beads turn yellow, I have done it ever since. It does make a difference.

    1. First, make sure it’s truly polymer clay. Be aware that sometimes plastalina-style modeling clay is sold as polymer clay and that stuff will melt into a goo when baked. Most every polymer clay will bake just fine at 275°F (130°C). Make sure to cover it during baking and bake it for at least 30 min per 1/4″ thickness. I’d do a test bake before you bake anything you’ve put a lot of effort into. Good luck!

  17. I’m so glad I “stumbled” on your website and these fabulous, informative articles!
    Thank you. I look forward to each new installment 🙂

      1. Thanks, Ginger! I do have a convection oven, and I recently bought two thermometers for it–one for the front and one for the back of the oven. I was
        shocked to discover a 25 degree difference from front to back! When the rear thermometer is at the correct temperature, then I put my pieces in, and position them closer to the back than the front. I’ve had success using this
        approach. I know that convection relies on a fan to distribute the heat more
        evenly, but still there is no unified temperature in the oven. I’m really con-
        vinced that two thermometers per oven is a good idea.

  18. Is the baking temperature different in a convection oven? My oven can switch between conventional and convection, which do you recommend? Thanks so much for sharing your wisdom…I am learning a lot this morning by just reading through your blog posts and tutorials.

    1. I don’t have a convection oven, so I’m not real up on how they work. But I do know that temperature doesn’t change when it comes to polymer clay. The chemical reaction happens at a certain temperature, so you need to set your oven to whatever that temperature is (as per the instructions for your brand of clay). Now remember to verify with an oven thermometer, because most oven thermostats are inaccurate. I think you could go with either setting, but I don’t know for sure. Maybe someone who uses a convection oven will chime in and give use some more info.

      1. Maybe I’ll just stick with using the conventional mode for now. Convection also bakes faster, so there’s that issue too! Thanks so much for your prompt reply.

  19. Hello, this was incredibly helpful! Although, today I created and baked my very first polyclay miniature, and I’m sad to say that even though I kept it in the accurate temperature zone for the accurate amount of time, wherever the miniature made contact with the surface it was being baked on, turned a light brown! It’s a small flat spot surrounded by a faded yellow, although the rest of the mini is perfectly white and fine and hasn’t touched the surface. I used Premo! Sculpey, and cured the creation on a metal pan covered in aluminum foil. I’ve read that the metal can absorb the heat and over-bake the areas which are in contact with the metal? Is this what happened, or something else..?

    1. Oh no, I’m sorry to hear about that! I’ve not had this specific problem, but it does sound like contact with the metal might be the cause. To prevent future trouble I’d do two things. One, place a ceramic tile in the pan. That will help the heat stay more even inside of the pan. And two, bury your little miniature in some baking soda. That would keep it covered and protect it even further against the heat. It sounds like your oven is touchy and the temperature gets very hot while the element is on, acting more like a toaster than an oven, if you see what I mean. So protection is your solution. Let me know how it goes.

  20. Margaret Ashley

    First time visited your site. I have bought several Dvd’s from Tv sites but yours has been the most informative. Great site, thank you, Margaret

    1. Thank you so much, Margaret. It’s so frustrating when you have questions and get conflicting, incorrect advice so I work hard to give good information and provide a valuable resource for clayers.

  21. Well done, again Miss Ginger. I totally agree with the Bake Time issues. All I can say is, I sure could have used this wonderful advice when I was first starting out. This is great information, Ginger. I hope more of the Clay Mags / Blogs add this to their resource vaults. Definitely, well done.

    1. Well thank you Kate! The information is out there, but it’s lost in blogs and posts and comments and on forums. It’s not brought together in one spot. I’m trying to do my little bit. I am glad that people are reading it and finding it helpful.

    1. Thank you Anita. I struggle with the words the most. I know what I want to say…but organizing it and not rambling…that’s so hard! I wish I’d learned more about writing in school. It’s so necessary in our lives!

  22. I appreciate this thoughtful and detailed discussion, having just lost a big project to an oven that had degraded its ability to hold temperature. What I also found out, sad to say, was that the little temperature gauge had also degraded and was not accurate. So they might be cheap, but also, they might be useless!

    1. I’m sorry to hear that! So frustrating. I think we’ve all had our projects ruined at the baking phase for one reason or another. Yes, a thermometer might be useless if it doesn’t work, true enough. And I have had one break…it just got stuck at zero one day. But having one is better than not, definitely. And maybe more than one!

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