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

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 and never 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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186 thoughts on “Avoid These 10 Sculpey Mistakes (and other clays, too!)”

  1. Hi Ginger, love your site and tips!

    I am new to jewellery making and started out with Sculpey III because it was available but obviously it was a bit of a disaster!

    I have just started working with Premo & Soufflé and am loving it so far. However I’ve noticed a couple of stud earrings have a very fine hairline crack in them. I baked at 130C for 30 mins. Do you have a suggestion on how to prevent this happening and is there a fix?

    Cheers, Kate

    1. Cracking is so frustrating and there are as many causes as there are stars in the sky. (Maybe not, but close.) The usual culprits are flexing while still warm or having a stretched layer over one that’s not stretched. To fix, just rub a bit of liquid clay into the crack, wipe clean, and bake again. If it’s bigger, use matching clay. You might need to sand it to make it invisible, or use varnish or resin.

  2. Hi, I just started working with polymer clay, I am having issues well before the baking phase. it cracks and breaks, I fix and a day later it breaks or two weeks later. I am starting to think this will never work out. Should I try finding another clay to work with to make my resin stuff. Is it because the clay was too dry to start with I did add water and oil to help but it doesn’t seem to be doing much. Thanking you in advanced.

    1. Polymer clay doesn’t crack before baking, generally, unless it’s flexed. You didn’t say what you’re making or what brand of clay you’re using. But you shouldn’t be adding water or oil to polymer clay. Conditioning is key when it comes to polymer clay. If you’re building a sculpture, make sure you’re using an armature to support it or things will definitely crack as they fall from their own weight.

  3. I use Liquid Sculpey to paint colors on polymer clay sculptures. How do I keep it from blistering when baked? Also: can I use it on a small ceramic dish and bake it? It’s not for food use. Will the Liquid Sculpey peel off after it is baked?

    1. If anything is blistering when it’s baked then your oven is likely too hot. Liquid sculpey can be applied to a dish and baked, yes. It might peel afterward, yes, but it depends on how thick the coating is.

    2. try baking it first then paint it bc then if it accidently gets burned it won’t show when you paint it.

  4. Hi,
    Thank you for your article. I need ornament shape with a topper (hanger) for a memorial. I am looking at making 25 ornaments from white clay. They need to be 4″ wide x 1/4″ thick. If I make these how do I get the hanger in without making a lump in the clay? Or is it better to use a 4″ ornament cutter with an attached topper on it? I’ve never worked with this medium before so I hope you can help!

  5. Hi, I have some Sculpey III and have made a few earrings and I would like to use up my supply so that it’s not a waste. I notice you recommended not to use it ’unsupported’, can you give me any advice on how to reinforce the drill holes so that they won’t break?

    1. I mean that drill holes won’t hold in thin pieces of Sculpey III because it chips out due to the clay being quite fragile and brittle. (That’s why it’s not good for making earrings in the cookie-cutter style…the whole earring will be brittle.) I wasn’t just referring to that specific style of earring. I meant in all kinds of polymer clay creations…don’t use these brittle brands of clay without supporting them with an armature, metal, or a base of a strong brand of clay. These brittle brands should not be used at all in thin things like cookie cutter earrings.

  6. Hi Ginger! Thanks for the tips! Fully agree with the need for kink in eyepins.. my difficulty is how to insert it into the finished clay neatly without accidents (eg kink pokes through the clay). Appreciate any tips on this. Thanks!

    1. It’s not hard, you just have to reform the clay a bit. If a kink is too hard, make a loop instead. It doesn’t matter what shape you make, just make something so the pin doesn’t just pull straight out.

  7. Hi: Have a tin ‘goat’ in the garden whose feet has rusted almost away. Can I build up some feet and attach them with clay and then seal and put outside? Thanks! I know this might be unusual…

    1. I don’t see why not. As long as you can fit your goat in the oven. 🙂 But don’t varnish. That thin layer of plastic (the varnish) will not hold up in the elements. Polymer clay does not need to be sealed.

  8. Hello! Thank you for the tips. I did have a question.
    I use clay softener made by sculpey to brush away fingerprints. It was working great, but suddenly, I have noticed that after I bake my clay, the bottom or whatever rests on the foil is still oily and tacky from the softener. I tried baking again for longer and there was no change. Do you know what could be causing this issue suddenly? I was making small dragons with fimo clay and I haven’t changed the brand or anything.

    1. Clay softener is pure plasticizer and it’s the diluent of the clay. It’s “clay juice”. It will absolutely soak in and soften the clay. I don’t know why this suddenly changed for you. Perhaps they’ve changed the formulas of something. But it’s definitely expected behavior.

  9. I have a bunch of polymer clay beads that I bought years ago from a seller. I’ve discovered they are all brittle and I can easily snap them in half. Are these useable at all? Can they be coated or used in resin? Thank you for your help and informative article.

    1. You can often cure them properly to get more durability. Coating in resin can also make them more durable, to an extent. Yes, you could add them to a resin pour, making them embellishments embedded inside.

  10. Hi, l’m wondering if I should waste my time on some several year old Super Sculpey which was not stored in a plastic bag…. Or just go get some new.

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