Avoid These 10 Sculpey Mistakes (and other clays, too!)

When I started working with polymer clay, I made a lot of mistakes. (I still do, by the way.) But experience has taught me a few things and here are some mistakes that I no longer make. (These tips apply to all brands of polymer clay, not just Sculpey. Read on if you use any oven-bake clay brand!) Nobody likes to have their work break, burn, melt, get sticky, or fall apart. Ruined projects are disappointing, but it’s even worse when we’ve given things as gifts or sold them to customers only to realize they’re falling apart over time. So whether you’re new to the world of Sculpey, Fimo, and polymer clay or whether you’re an old pro, it doesn’t hurt to take a moment to check these out. Avoid these 10 Sculpey mistakes and spend more time enjoying your work with polymer clay.

1. Using Weak Polymer Clay for Thin Pieces

Underbaked polymer clay will crumble. How long to bake polymer clay? Read more at The Blue Bottle Tree.It is so sad to work hard creating something that breaks when it’s worn or used. It’s even more horrifying to realize that you’ve sold something that is made from weak clay and won’t be durable. Not all polymer clay brands are created equal and each has its uses and purposes. For making things that are thin or have areas that are thinner than 1/4″ (6mm), make sure that you’re using a strong clay such as Premo, Fimo, Pardo, Kato, Cernit, or Souffle. Sculpey III, Original Sculpey, Super Sculpey, and Bake Shop are all quite brittle after baking and should not be used, unsupported, in any area thinner than 1/4″ (6mm). These weaker brands do have their uses, however, so save them for other projects. Here’s more about choosing the best brand of polymer clay for your project.

The stronger brands of polymer clay are durable enough that you cannot break them with your hands, even when used as thin as 1/16″ (1.5 mm). Of course to have this kind of durability the clay must be properly baked, which leads us to the next point.

2. Underbaking Polymer Clay

Polymer clay is made from PVC powder, plasticizers, binders and fillers, lubricant, and pigments. As the temperature increases during curing, the powdered PVC softens in the plasticizer and the particles begin to absorb the plasticizer. Optimally, the particles will eventually fully fuse together and form a solid mass of plastic. If polymer clay is underbaked, the fusion will not be complete and the resulting clay mass will be weak. Underbaked clay is not only less flexible, it is susceptible to breaking and crumbling. Underbaked polymer clay can also have excess free plasticizer that can lead to cure inhibition in paints and glues, causing them to remain soft and/or sticky.

To properly bake polymer clay, you must consider both time and temperature. The temperature on the package is a guideline, and you do have some leeway. But you really do need to bake at a sufficient temperature for at least as long as the time stated on the package. Most ovens are inaccurate and it’s important to use a separate oven thermometer to know what temperature your oven actually is. (I like this inexpensive digital probe thermometer, but there are many others.) In the real world, even accurate ovens fluctuate during the baking cycle (and when you open the door). It’s therefore best to bake quite a bit longer than the label suggests to make up for this.

Use oven thermometers to verify the temperature of your oven when baking polymer clay. Most ovens lie.
I use two digital probe thermometers to verify exactly what temperature my oven is during baking. I’ve been quite surprised to see that my oven’s dial is often off by 40°F or more.

Polymer clay should be baked for at least 30 minutes for each 1/4″ of thickness. This means that a 1″ thick bead will need to be baked for two hours. Yes, this is correct. If your oven is truly baking at the correct temperature, your clay will not burn. Lighter colors may, however, discolor, so it is always better to do multiple bakings of thinner layers. Want to learn more? Here’s my class on baking polymer clay that gives more info about choosing an oven, baking temperatures, and knowing if you’ve baked your clay long enough.

Burned and blistered polymer clay is a result of using an oven that heats to the wrong temperature. Learn more Sculpey Mistakes to Avoid at The Blue Bottle Tree.

3. Burning Polymer Clay

Let me be very clear. Polymer clay does not burn unless it reaches temperatures near 350°F (176°C). (Fimo is a bit more sensitive.) If your project actually turns black and bubbles, then your oven is way too hot! As already state, ovens can be wildly inaccurate. When the oven’s heating element cycles on and off, the heat radiating from it can be tremendous. If your project is close to the element, your thermometer could be reading the correct temperature but your project could still bubble and blacken. If you have burned polymer clay, you need to address your oven, not your baking times.

Many people assume that baking longer times at lower temperature settings will solve this problem. It’s common to read recommendations in forums to set your oven to, for instance, 215°F (100°C) and bake for an hour or so. Will this work? Well, it might work for a specific person because they’re compensating for an incorrect oven. What they think is 215°F might actually be 275°F in their oven. But when others follow this temperature advice, they end up with fragile, brittle, underbaked clay.

Light colored or translucent polymer clay will commonly discolor and darken during baking. This is not the same thing as burning. To prevent this, first make sure that your oven truly is baking at the correct temperature. Then cover your pieces to prevent the oven’s element from toasting your polymer clay project. For more info on covering clay and preventing browning, see my class on Baking Polymer Clay.

4. Using Nail Polish as a Polymer Clay Glaze

Are you making these 10 Sculpey Mistakes? Learn more at The Blue Bottle Tree.It’s very common to see polymer clay projects, especially on craft blogs, that recommend using nail polish as a glaze or gloss finish on polymer clay. It’s convenient, it’s simple, and seems like such a good idea. Except that it’s not. As many, many people have found out, nail polish on polymer clay will very often turn sticky and goopy over time. Not all nail polishes are bad. Some work just fine. But there are thousands of brands of nail polish around the world and there is really no way of knowing which ones will work on which brands of polymer clay. Don’t risk it. Use a proper polymer clay sealer. If you need to use one at all. Yes, that’s right. You don’t actually NEED to seal polymer clay. Read more and learn which sealers are the best to use when you do want to use one.

5. Using a Spray Varnish on Polymer Clay

Do not use Krylon Crystal Clear Glaze on polymer clay because it will turn sticky over time.

It also seems like such a good idea to buy a can of spray varnish and give all your newly made Sculpey creatures a nice glossy coat of spray varnish. So simple and so easy. Except that the varnish never dries. There are very few spray varnishes that are compatible with polymer clay. And what works with one brand of clay won’t work with another. I tested many brands of spray sealer on polymer clay and only found two brands that consistently works with all brands of clay.

What if you’ve used a spray sealer and now your charms are sticky? Can they be saved? In some cases, yes. I found that 91% isopropyl alcohol removed most sticky spray sealers. It’s worth a try.

6. Storing Polymer Clay in the Wrong Plastic

Polymer clay is vinyl that contains a plasticizer to make the finished pieces more durable. That same plasticizer also softens other plastics, too. So there are some plastics that will be dissolved when left in contact with polymer clay. Because of this, you need to be careful to only store your unbaked polymer clay in containers that are compatible with polymer clay. Avoid using anything with recycle number 6 or 7 on it. Avoid contact between raw polymer clay and anything made of styrene, polystyrene, styrofoam, and ABS because it will soften and fuse with the polymer. This also means you should avoid contact with keyboards, Lego, many toys, and Bic Cristal pens, and those clear hard plastic pots that lip gloss or eye shadow comes in. The clear, brittle plastic storage boxes are a no-no, too. Learn more about polymer clay melting plastic in this article.

You can generally store unbaked polymer clay in plastic ziploc bags and any plastic box with a 1, 2, or 5 on the bottom. The floss box below works very well.

7. Not Washing Your Hands Before Working With Clay

Dirty hands make working with light colored polymer clay difficult.Related to the dust issue is one of making sure that your hands are clean before working with polymer clay. Even when you think your hands are clean…they’re not. And when working light colors such as white or yellow, or translucent, dirt that’s invisible on your hands can end up in your clay, giving your work dirty streaks. Even the blue residue from wearing blue jeans will coat your hands and show up on light-colored clay. So before working with polymer clay, wash your hands well, and don’t forget to clean under your fingernails.

Another trick is to have a ball of scrap translucent clay at your work desk. Roll this clay between your hands before working. It will pick up any loose skin bits, fiber, dirt, and dust. It’s also a great trick to do when switching from working with a dark color to a light one. When the clay gets too junk-filled, just toss it and make a new one.

8. Buying Too Many Tools…At First

It’s all too common for a newbie to find out about polymer clay and buy everything in the clay aisle at the craft store, assuming that it’s all required for working with polymer clay. Not only can this be very expensive, but you really don’t need most of the tools you’ll see for sale there. Start with some basics, then add more as your experience grows and you have a better idea of what you like to make.

There are plenty of polymer clay tools out there, and you want to leave enough money (and space) so that you can buy the things that will bring you the most enjoyment. So, what are the essentials? Here’s what I recommend to buy for your Polymer Clay Starter Kit. And when you do start buying tools, you can often find them quite cheaply when you start looking in creative places. Here’s more about finding cheap polymer clay tools.

9. Embedding Eyepins Without a Kink

When you make polymer clay pendants and charms, you’ll want to include a hanging loop. A lot of clayers take a commonly available jewelry eyepin, cut it to length, and insert it into the raw clay. But after baking, the straight wire of the eyepin readily pulls out of the clay. Some people glue the pin and push it back into the baked clay. That will often hold, but not always.

A better way is to create a small kink in the end of the eyepin, before you embed it into the raw clay. This way it cannot pull out after baking. Here’s an example of what I mean:

Always put a kink or bend in your eyepin before inserting it into polymer clay. Avoid these 10 Sculpey Mistakes.

10. Using the Wrong Glue with Polymer Clay

Superglue is magical and it can be an incredible glue in the right circumstance. But it’s not the best glue for polymer clay. At least not the usual inexpensive superglue that we all know and love/hate because the cap gets glued on (so frustrating). It is a very brittle glue and polymer clay is flexible, so when the clay flexes, the hardened glue will pop right off and the bond fails. It’s better to use a gel version such as Loctite Gel Contol or a higher end version such as Lisa Pavelka’s PolyBonder.

Cheap super glue is one of several popular glues that don't work well for polymer clay. Avoid these 10 Sculpey Mistakes, read more at The Blue Bottle Tree.

Another often recommended glue, especially for jewelry use, is E6000. While it can be a very good glue for some uses, it does tend to remain gummy never and fully harden on polymer clay. Many people DO have good results, but many others do not. I suspect the issue lies with the brand of polymer clay or perhaps the age of the E6000. But don’t be surprised if you find that this glue fails for you.

It’s always better to use a physical bond or a baked bond to glue polymer clay to itself or to glue metal to polymer. For more specific recommendation and glue strategies, visit my article What’s The Best Glue for Polymer Clay.

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160 thoughts on “Avoid These 10 Sculpey Mistakes (and other clays, too!)”

  1. Thanks for the article. I am using Sculpey (which I now know was a mistake) and followed the baking instructions 275 deg for 15 min. I’ve had issues with some of my pieces baking after I sealed them. Can I put them back into the oven after sealing to better cure, as 15 min was not long enough? I hadn’t had this issue with prior projects using Sculpey… I am using a Liquitex acrylic gloss varnish to seal.

  2. Thank you so much for a really useful post. I’ve just started dabbling with Polymer Clay. I’ve been informed that Polymer Clay isn’t suitable for coasters, and if it is used for coasters, hot drinks shouldn’t be put on them. Is that right in your experience?

    1. Hi Emma. There is SO much misinformation out there! Polymer clay makes great coasters. One caveat is that you most likely won’t want to seal them or use any surface treatments or varnish on them. Those tend to get sticky when left in contact with a hot mug for very long. But polymer clay itself? Awesome.

  3. Hi such a great article thanks! I just started experimenting with polymer clay and I found that when I take my pieces out of the oven they are often cracked (like small spiderwebs on the surface) what am I doing wrong?? Please help! Thank you! 😉

  4. Hi. I have a question. I am interested in making dolls, and to do so I know I would need to bake certain parts first the head, but when adding and baking the other parts how don I pervent my prebaked parts from burning?

  5. Thanks for the info on what to avoid! A friend had a paw print made in polymer clay after her beloved dog died, but never baked it as instructed. It’s now cracked and in pieces. She’s wondering if there’s any way to fix it. I don’t know whether patching it with fresher clay would work, or if the pieces could be baked and then glued together. Any ideas?

    1. It’s really hard to give advice on something like that. Usually, however, polymer clay doesn’t become permanently hard until it’s baked. So you should be able to “rework” it a bit and smooth the seams. But sometimes it’s not possible if there’s too much damage.

  6. So wonderful to have happened upon your article. I have a question I cant seem to find any answers for. I want to use Premo and I am making handle covers on aluminum crochet hooks. I have done this before and been very successful, so now my goal is to teach someone else coming in new to clay. Well she was describing some designs and I had a light bulb go off that I could use my cricut, cut out some vinyl and sandwich the vinyl pieces between colored and transparent clays. Will baking them cause any harm to the vinyl or clay itself? Thank you so much for your time in answering us all. I appreciate it much 🙂

    Mrs B.

    1. I think it’s always worth a try, but I’m not sure it would work well. One thing to be aware of is that polymer clay IS vinyl and the plasticizer in it might have unknown effects on the vinyl cutouts. Some people DO use their Cricut or Silhouette to cut unbaked polymer clay sheets. So there’s a whole world out there you might want to explore. There’s a Facebook group for Silhouette users called PCSilieLovers.

  7. I have a weird question and wasn’t sure where to ask for advice. I made a sculpture with Super Sculpey. I baked it and all was good (I think… it was my first time using Sculpey, and since the figure felt pretty hard after baking, I assume it was baked long enough). The sculpture has an armature and was bulked properly with aluminium foil. I left it for a few days and decided to paint it with acrylic paint. I painted thin layers onto the sculpture. Hours of drying time between layers. Then I left it alone for about a week and then decided to continue painting it… But the acrylic paint feels as if it’s sticky, and in some places I can peel it off.
    I am wondering what I did wrong in the process 🙁 Right now I am trying to remove the paint by carefully peeling it off. I have no idea what to do with this sculpture now… And I am working on another one, but I am so put off painting because I am scared it will be ruined too.
    I have no idea if maybe there was too much water in my acrylic paint? Or did I bake the sculpture wrong to cause this? Maybe my acrylic paint isn’t good enough? Any advice would be greatly appreciated.

    1. Sadly, it’s a chemical reaction between the polymer clay and the paint. Some paints will do this with polymer clay, especially model paints. Remove the paint if you can. Try using rubbing alcohol to dissolve the paint. Then you can paint it again with a different paint. But this time test the paint first.

  8. I bought two big blocks of Sculpey for my grand kids to play with about 12 years ago.They played with some of one block and never touched it again Today it is like a rock and I would like to make some of the teeny babies. Is it possible to soften it again?

  9. new to polymer jewelry making & have just made pendant & earring sets (1/8″ thick, after running through largest setting on pasta machine). Baking advice for my clay says 15mins for each 1/4″…. so, I baked for only 8 mins….
    After reading these tidbits of marvelous information, I’m wondering if I should rebake them, and for how long?? HELP!

    1. Definitely rebake them, and I’d go for an hour at 275°F, assuming you’re using an oven thermometer and you know your oven is correct. Also, since you’re using Sculpey III, beware that it’s a brittle clay and won’t be durable when that thin. Try using Premo or Souffle to make jewelry. Always bake any clay at least 30 minutes, usually longer. Don’t go less than 30 min even for thin pieces because it takes time for the oven to heat back up again after opening the door. Have a look at my baking articles for more explanation. Thanks!

      1. Mackenzie LeBlanc

        I’ve tries increasing baking time for Sculpey jewelry as you’ve recommended, but find the dangly earrings feel somewhat bendy after the longer bake time. Is this normal? Should I make them thicker?

  10. This was such a fun read! I have one little detail to add to point 6, referring to storage and buying a limited amount of polymer clay. Sometimes it is best to buy the extra clay while still fresh and store it in air tight containers to preserve them, because I do notice some stores still have the same batch from my last purchase after months. In other words, the clay they are selling becomes hard to the touch, but it’s still on sale either way. And when buying online, you can’t ‘feel’ the clay you are buying, sometimes ending with an old hardened block instead of the fresh and soft ones.

    1. Yes, stores often keep their stock for a long time. Online sources typically have a much greater turnover and the clay is usually very, very fresh. The problem with stocking up is that some clay brands get harder over time, regardless of how they’re stored.

  11. Hi.
    I hope you can help me with my problem. I do not make jewelry from polymer clay, instead I make things for dollhouse 1:12. I have made a lot of beet root canes (3 to 6 millimeters thick), that I firstly baked for 30 minutes. When finished they were extremely bendy yet brittle, so I baked them for another 20 minutes. Normally I would be able to cut very fine slices without a problem, but no matter how I cut and no matter how sharp the knife, it just crumbles into tiny pieces. My theory is that I have baked them so long, they became too dry. Is there any way I can save them? For example soak them in oil?

    1. Generally, polymer clay only becomes tougher and less brittle the longer you bake it. It does not “dry out”. Your 30 minute bake was likely not hot enough and the second bake of only 20 minutes was not long enough to allow complete fusion of the clay mass, especially if your oven is not hot enough. Get an oven thermometer and adjust your oven to the correct temperature (most dials are wildly inaccurate). Then bake your can for an hour. That should solve the problem.

      However, slicing baked clay is always tricky. Not all brands are “elastic” after baking and will be susceptible to breakage. Make sure you’re not using Sculpey III for this as the clay is quite brittle after baking. I’d use a brand like Fimo Professional or Cernit to be flexible enough to allow easy slicing after baking. Also, you’ll likely want to heat the cane before slicing.

  12. Benjamin Stevens

    I have watched several you tubes from Giovy Hobby. Does anyone know the type of polymer clay the use. When it comes to carving details like he shows my clays just don’t hold up. I use mostly Sculpey

  13. Hi Ginger,

    Thank you for sharing all of this helpful information!

    I really want to try using liquid clay on some of my charms. Is it okay to use sculpey liquid clay on fimo clay? I always worry about baking too long and leaking chemicals into my oven.

    Thanks for your help!

  14. can anyone tell me if i can use a metal bowl as mold for cooking polymer clay in the oven or should i use a glass bowl?

  15. Hi Ginger, I am a middle school art teacher and I stumbled across your site looking for answers on crumbling clay. I was wondering if you could give me advice on keeping Sculptey clay from crumbling on foil armatures before they are baked. I have to bake 130 sculptures with foil armatures over several days, so during that time ( even though they are in Ziplock bags) some of the clay begins to crumbling off the foil ( I have added masking tape to the foil-mummy style and that helps some). I tell the students to work the clay first, then to apply thin ( no more than 1/4 inch layer), and then to smooth over seams and cracks, but still I seem to spend hours fixing cracks of sculptures I can’t get to for a day or two. Thanks

    1. Polymer clay won’t dry in the air, so it shouldn’t be crumbling and falling off the armature on its own. Is someone disturbing them? Polymer clay will sometimes crack when re-worked after a long period of time, and sometimes cracks can appear, but not usually in a few days. This makes me think you might be using an air dry clay instead of polymer clay? Which brand are you using?

  16. Great tips, especially your tips on baking. I recently completed a piece that was very thick…probably 1.5 inches in the body. I baked for about 23 minutes at 275 (or so my oven claimed anyway). To my dismay, after taking it out, I noticed several hairline cracks. It took days to create the sculpture, so I tried using liquid polymer clay cured with a heat gun (I use genesis heat set paints). This covered the cracks, but as I added and cured paint, more cracks just endlessly sprung up. It was a real disappointment. So I’m guessing 23 minutes for 1.5 inches is not nearly enough time, and I need to check the temp on my oven. I was pretty confident my build up and preparation of the clay was ok (the clay is the Sculpey Firm, and I buy 3 boxes at a time from Amazon, which is usually dry and crumbly until I add clay softener throughout). Hopefully the baking process is my issue :-). Thanks!

    1. There’s more than one thing going on here. Underbaking is an issue, certainly. But also, baking anything thicker than 1/4″ at a time runs a huge risk of cracks being formed. Always bake a center first, then add more clay on top of that, making each layer no thicker than about 1/4″ thick with each baking. You can also use a compressed foil core instead of baked clay. The point here is that thick pieces cure on the outside while the inside is still being cured. This causes cracks on the outside.

  17. Thank you for all the information. I have a question about the digital thermometer for checking the oven temperature. Because they have a probe that is designed to be inserted into food, where do you place the probe? Just lay it on the oven rack? Thanks in advance for the answer.

    1. Yes, just lay it on the rack in the oven. It will fluctuate more than a dial thermometer will because it’s sensing minute changes in the temperature as the oven cycles. But in my experience it will generally show the correct temperature.

  18. Ginger, my daughter made a bunch of covered pen barrels for Christmas gifts and we followed directions in her sculpey book for baking. The pen barrels all melted and the sculpey split all over. It was so heartbreaking and she had put so many hours in to these. What went wrong???

    1. Oh no! That’s awful! The problem was that the wrong kind of pen was used. Some pens will expand in the oven, causing the clay to split and fall off. The best beginner pens to use are Bic Stic pens. Don’t use generic ones from the dollar store…many are the wrong kind of plastic. I’m surprised that the Sculpey book didn’t tell you what kind of pens to buy. If they didn’t, I’d contact them and tell them your experience. Please have another go at it. It’s hard to start over, but setbacks are a lesson for kids to learn, too. She’ll be even more experienced the second time. 🙂

  19. Hi Ginger! Thank you for all your great tips! I have a question regarding sealers/glazes. I found a cute video on polymer clay earrings and have made some encased in brass. The light coloured clay ones have faded or discoloured after applying a sealer. I used Mod Podge Dimensional Magic after my items cooled. The video had suggested using this but the light coloured clay has totally faded!
    Any suggestions?

    1. I’ve never had polymer clay fade after applying any varnish or “sealer”. I’m not sure what’s going on. Are you sure the Dimensional Magic isn’t cloudy and it appears that the clay has faded? It’s quite common for dimensional glazes to turn cloudy. You can read more about the various types of clearcoats and why dimensional glazes aren’t the best thing to put on clay in my article on Understanding Glazes, Sealers and Varnishes.

  20. Rebecca Doremus

    Hello Ginger and thank you for this terrific article on surface treatments and sealers. I was wondering if you have ever tried using Kiwi Neutral Shoe Polish, Magic Shine for shoes, wax or Renaissance Wax for the same purpose? I have used all of these on small pieces in a very thin layer and then buffed. Each is a little different than the other and I primarily use it on Sculpey III and Premo (all versions). I have had great results and a little goes a very long way.

  21. Great Article! Thank you. You approach poly clay problems as a scientist! I will keep this article, and reread it. Thanks for helping me avoid some of the same mistakes.

  22. Pingback: KatersAcres 15 Common Polymer Clay Mistakes You Need to Know - KatersAcres

  23. Thanks Ginger, With your MeasurePro thermometer, can you leave the probe and cord on the oven the whole time youre baking or are you testing at certain times only ? Im looking at a similar one here in Australia

  24. Thank you, Ginger.

    So, when you say not to use nail polish as a glaze, I assume that would apply to using it like a paint, to colour the surface of areas of the clay? RATS! I have some gorgeous colours of polish, and I never do my nails lol! I bought it all for playing with my polymer clays. Oh well, I want to try resin pouring paintings, and I may be able to incorporate the polishes into that.

    1. Oh no! Well, nail polish isn’t always a bad thing. Some polishes work with some clays. So if you have them already, go ahead and give it a try. I don’t generally recommend using them because it’s pretty hit-or-miss. But since you have nothing to lose, give it a try.

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