How to Keep Your Precious Creations from Burning & Cracking

Posted on 13 Comments
How To Keep Your Polymer Clay Creation from Burning or Cracking by KatersAcres


How To Keep Your Polymer Clay Creation from Burning or Cracking by KatersAcres

There is truly nothing that makes me more sad and angry than spending hours making something gorgeous only for it to burn & or crack.  This is horribly frustrating for every polymer clay artist.  Today I’m going to give you my best hints, tips, & tricks to preventing this.  We’re going to go back to basics and learn how to bake polymer clay.

In my opinion, cracking objects is often worse than burning objects.  Objects that are burned can often be covered or disguised by antiquing, covering in a paint medium, using Perfect Pearls, or even Swellegant‘s line of products by Christi Friesen.  However, when a project cracks, there is not a lot that you can do.

OH NO! It cracked!

Any oven, whether your home oven or toaster oven is unreliable and has massive temperature fluctuations. I know even as I type this, you don’t believe me…but it’s true. But don’t worry or fret because there are some easy and quick solutions that you can do to solve this problem on your own that are cheap, cost-effective, and will make a drastic difference in how your clay is baked and will keep it from cracking and burning.

Don’t Let it Crack

There’s a couple of important steps in keeping your precious creation from cracking.  Cracks can appear as hairline, tiny fine cracks in just the surface of the clay to huge fissures that run along the majority of a piece. A basic how to bake polymer clay instruction guide is below.  90% of the time, it is one of these reasons that your clay has cracked while baking.

How to Bake Polymer Clay - Oven Tips by KatersAcres
  •  The first and most important is to make sure that your clay is fully conditioned.  Clay that is not proper or fully conditioned has a better chance of cracking while baking.
    • Point of note: Sometimes poor clay quality (cheap clay) will do this regardless and there isn’t much that you can do about it except change to a higher quality of clay with a better manufacturer. Read this post here for more info.
  • Make sure there are no air bubbles in your clay. Trapping air bubbles while conditioning clay is another top source of cracking in your clay. Air bubbles will also cause cracking in undesirable places if you are not careful.
  • Keep your oven at a constant temperature.  Most countertop ovens do not have good seals.  This means that the temperature inside the oven will vary by as much as 50 degrees.  This will cause your oven to lose its temperature drastically and spike as well. Both of these things cause your pieces to crack.  
    • PRO TIP: Use an oven thermometer to be sure that your oven stays at a constant temperature. I like this magnetic one and put it on the inside back of my oven. There are made for stovepipes and are perfectly safe for your toaster oven and polymer clay.
  • Use ceramic tiles to help hold your oven’s temperature.  I placed 4 ceramic 4×4 tiles in the bottom of my oven as well as two larger 12×14 tiles on the top and back of my oven to cover the vents.  This helps hold the temperature of the oven steady.  It’s a cheap fix and it will help your clay so that won’t crack anymore by acting as an insulator for your oven holding the temperature more steady and constant.

Don’t Let it Burn

There are really only two reasons that your clay will burn.  The first is that you are baking your clay above the recommended temperature. Always read the package for the particular brand of clay you are using to make sure that you are baking it at the right temperature. It is better to bake your clay longer at the recommended temperature than higher for shorter amounts of time. The second reason your clay will burn is that it is too close to the heating elements.  There’s a simple solution to this too. Move your piece away from the heating elements into the center of your oven and tent your piece with foil. It works, every time!

Sculpting Blessings,


13 thoughts on “How to Keep Your Precious Creations from Burning & Cracking

  1. nice

  2. Hi,

    I have been covering glass with translucent clay and cracks appear days after the project is complete so i don’t want to sell any of it or give it as a gift. I have been having a hard time pressing the clay onto the glass and getting rid of all the trapped air between the clay and the glass. Any tips you can share? Should I coat with liquid sculpey or cover the glass with a thin base of clay and bake that first? I’m pretty frustrated by now but I don’t want to ditch covering glass in polymer clay 🙁


    1. I have not covered a lot of things with glass, but the few I have, I have not had any issues with. Are you using cane slices per chance? Cane slices will often crack because they haven’t been reconditioned and instead have just been pressed onto the glass. The lack of conditioning (think reducing your cane) will cause them to crack. Cracking clay is often due to UNDER conditioning. Make sure your clay is FULLY conditioned before adding it to the glass. Fully conditioned clay should not have any “cracks” on the edges after running through the pasta machine. Many people STOP conditioning when the clay feels “flexible” … but cracking edges means it’s not fully conditioned. I would NOT cover the entire glass with liquid sculpted. Your pieces will slip & slide and you won’t like the result. See if the above doesn’t help you. If not, come back & we’ll try to figure it out together.

  3. do you lay the tiles in the bottom on top of the elements, that is what it looks like?

    1. Kathay, That’s what I have done in my oven, yes. Some elements in some ovens are also on the top, but there is no way to line those.

  4. I’m very new to sculpting but I have had much experience with cracking here’s what I do works every time and I don’t see any cracks after wards okay so I apply more of the same clay to the cracks wet a medium hand towel put my oven at its lowest setting and wrap my piece in the towel and put it back in thee oven for 20mins
    I hope that help alittle

    1. I haven’t tried this, but I rarely (once a year) have anything crack. I will let you know how it works for me.

  5. I have to disagree where cracking is worse than burning. Burning polymer clay releases toxic fumes into the air which is not good at all and you never want.

    Just a helpful tip from experience. To prevent either cracking or burning, you can bake in a pan of baking soda, cover the items in baking soda and then tin foil or lid. After baking, allow to cool completely before removing any clay pieces. Cracking is caused by the clay pieces expanding and contracting from the heat and then cooling if there is any air pockets trapped inside or under any layers where covering them with the baking soda prevents this from happening so much and provides a more constant environment.

    Also, as Alecia, mentioned, cracks can generally be “back-filled” with clay moistened with liquid clay. However, the object can crack again during baking unless it is buried in the baking soda.

    Since I have used this method I have never had an item crack on me in years. It does work.

    1. Hi Carolyn! Thanks for stopping by. I love the work you and your hubby do – GORGEOUS!

      I do know that the fumes are toxic, I had a fan built into my studio just for this reason (though I’ve only burned 2 things in 5 years … knock on wood). I do know that baking soda works, however most of my items range from 2″-6″ tall. This would be a TON of baking soda to bury them in. I just cover my things in foil.

      I must be doing something wrong as when I “back-fill” with liquid clay I can still see the crack and this bothers me. Perhaps if I filled it wil really softened clay of the same color? That might work!

  6. One way to fix small cracks is to create a ‘slurry with a small amount of the clay you used in the project with liquid clay. Make a thin paste, and smooth it into the crack (I use my finger) – bake for 15-20 minutes and cracks are gone. It might require a tiny bit of sanding to remove the shiny look of liquid clay… 🙂

    1. That’s a GREAT tip! Thanks!

  7. Katie – Thanks for the ‘tenting’ suggestion. Hugs!

  8. You are so right Katie, there is so upsetting to spend so much time creating a piece only to have it crack. Good tips here, thanks for sharing!

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