The Biggest Polymer Clay Mistake: Why Incorrect Baking Ruins Your Work

By Lelalo

About This Series

Hi, I'm Leah, I’m a handmade polymer clay artist passionate about bright, colourful pieces and expressing yourself through your creations. This series is about sharing my experience to help you avoid common pitfalls in this craft. Whether you’re just starting out or looking to improve your skills, this series explores the most frequent mistakes polymer clay artists make, in an attempt to smooth out your learning process. Each post explains why these mistakes happen, how they can affect your work, and what best practices will help you create stronger, smoother, and more professional pieces every time.

The series includes:

• Improper baking

• Working with dirty hands or surfaces

• Using the wrong tools

• Mixing incompatible materials

• Rushing the process

• Making pieces too thick or uneven

• Skipping finishing touches.

Thanks to scheduling internet magic, some of these posts may already be up by the time you're reading this, so go check them out!

Why Incorrect Baking Ruins Your Work

If you've ever spent hours sculpting the perfect piece with polymer clay, only to find it brittle, scorched, or cracked after baking, you're not alone. One of the most common—and frustrating—mistakes people make when working with polymer clay is baking it incorrectly. This issue can occur with any kind of piece- a sculpture, trinket dish, pair of earrings and one key part of using polymer clay is to watch your oven like a hawk until you're used to how it works. It might sound simple, but misunderstanding how polymer clay cures in the oven is one of the fastest ways to ruin a project. So why does this happen, why is it such a problem, and what can you do to avoid it?

Many people assume that baking polymer clay is as easy as following the instructions on the package. And while manufacturers do provide general guidelines, there are several variables that can lead even the most well-intentioned artist astray. Most home ovens fluctuate in temperature by 10-20 degrees Celsius without you realising it. If you rely solely on your oven’s built-in dial, you may be baking your clay too hot or too cold without knowing it. The issue with this is that generally Polymer clay needs 130 Celsius to cook, it won't cook properly at 125, and it will burn at 150.

Additionally, people often shorten the baking time to avoid burning or assume thinner pieces need less time, which is a myth. Polymer clay needs both the right temperature and the right amount of time to properly cure.

Incorrect baking, whether too hot or too short, leads to serious problems. If the clay is underbaked, it will be weak and prone to snapping, even if it appears solid on the outside. Overbaking can cause discolouration, burning, and bubbles beneath the surface. In both cases, the final piece either doesn’t last or looks unprofessional. There’s nothing worse than finishing a detailed sculpture or piece of polymer clay jewellery only to have it break with a small amount of pressure—or worse, melt into a charred blob in your oven, leaving you as a melted blob on the floor.

The good news is that baking polymer clay properly is completely achievable with a few adjustments. First and foremost, always use an oven thermometer. This is an inexpensive tool that takes the guesswork out of baking and tells you exactly what temperature your oven is actually reaching. It’s one of the simplest yet most powerful tools in your polymer clay toolkit. If you're wanting to make a lot of pieces, you could splash out on a mini toaster oven, the smaller size makes the internal temperature more even than your typical kitchen oven.

Next, follow the baking instructions based on the thickness of your piece, not just the time on the package. Most polymer clays require baking at around 130°C for at least 15–30 minutes per 1/4 inch of thickness (6.35mm for us metric users). This means a thicker piece may need to bake for over an hour. That’s okay—polymer clay doesn’t burn if you keep it at the right temperature. In fact, longer baking times at the correct temperature help the clay become stronger and more durable.

To protect your handmade piece during baking, place it on a tile and cover it loosely with foil or an inverted baking dish. This helps insulate the piece and prevent browning from direct heat.

I've had a few of my pieces burn in the oven, some early versions of my handmade earrings didn't make it through, which is a big blow when you've spent hours in the creation process! By taking these simple steps—using a thermometer, baking for the right amount of time, and protecting your pieces—you’ll avoid one of the most common mistakes in polymer clay and set yourself up for durable, professional-quality results.

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