Why Does My Pottery Clay Break After Baking? — Spinning Pots

Compared to the other steps and processes of pottery making, baking the clay might seem to be easier. But it’s certainly not. There are plenty of tricks that need to be maintained while baking clay.

Baking plays a vital role in crafting pots by turning a simple lump of clay into a ceramic ware. Here, the clay is heated in a high-temperature range so that it can go through a lot of changes. In the first phase, the water bonds present in the clay starts breaking apart. The second phase leads to the complete evaporation of moisture from the clay. And the final stage makes the clay semi-porous with a stone-hard surface.

Baking is usually done to turn a soft and pliable clay into a hard pottery piece, which can bear daily usages. Henceforth, it provides the clay with enhanced strength to become too tough to get washed away with water.

However, mishaps are unpredictable. So, at times, disasters like breaking of the clay during baking or post-baking might happen. But do you know why this issue occurs? Well, there are several reasons behind this kind of mishaps. And knowing the exact cause behind this problem will help you to work on it and prevent such disasters in the future.

So now, let’s start with the facts that you must know about the breaking of the clay after baking.

Things to focus on:

While baking pots, always remember to use polymer clay type. It is so because only polymer clay reaches out to maturation through baking. Other varieties of clay, including earthenware, stoneware, and kaolin, are too strong to be baked and require super high-temperature for firing. Following we have given a few reasons why clay breaks off after baking and how you should treat it during the process:

1. Wrong temperature set-up and baking time:

You can’t ignore the fact that various types of clay require different temperature set-up to reach the maturation stage. When the temperature set-up goes wrong, it harms the clay texture and leads to the breaking of it. Here’s what happens when the temperature set-up and heat distribution doesn’t occur evenly.

Besides, the baking time plays a crucial role in deciding the fate of your ceramic ware. Though each variation of polymer clay has its own set of baking time duration, the average time for baking a clay should be 35 minutes. Baking for some more time attributes the clay with more strength. But exceeding the time for too long is not at all suitable for your ceramic.

Thus, it is necessary to bake your clay for an apt timing.

Nevertheless, the baking temperature and time go cohesively. While baking, you need to take care of both these factors.

Here’s a temperature graph that you should follow while baking polymer clay.

To solve temperature and baking time-related problems, you need to follow some essential tips to avoid such clay breaking.

2. Unstable oven temperature:

You might have already understood the importance of baking temperature. But the source of the temperature also plays a significant role in deciding the perfection of your baking process. Sometimes your oven might provide you with fluctuating temperature. This sudden interruption in oven temperature facilitates uneven baking, which can very likely cause damage to your polymer clay.

However, don’t worry. You can easily fix this problem to save your polymer pottery from such kind of damage.

3. Variation of clay thickness:

It is a more likely concern to consider clay shaping rather than baking. While building the structure of your pot, if you don’t ensure even thickness throughout its body, then it will end up being a non-uniform surface. Uneven thickness in different places also creates trouble during the baking process.

To avoid such problems, you should take proper measures.

4. Improper drying of clay:

It is essential to dry your clay properly before placing it inside the oven for baking. Once you are done with giving a shape to your clay, you need to let it dry. An improperly dried clay can ruin your entire pottery project when it comes in contact with high temperature.

5. Using a weak clay:

While working on a pottery project, you have to make sure that your clay is strong enough. Weak or feeble clays tend to have a lesser amount of plasticity and bonding compound, which hampers the durability of the polymer.

6. Using improper glazing substitutes:

Using the wrong kind of glazing substitute causes abnormal heat formation. Your polymer clay can’t be compatible with any random glaze, as their maturation temperatures won’t match.

Also, the presence of chemicals in the glazing mixture makes your clay undergo a lot of processes like fusing, oxidation, and reduction, which can have their own abnormal impact on your polymer.

Here are the types of glazes or paints that you should avoid using.

Spray varnish

There’s no doubt that a spray varnish gives a shiny and glossy coating on your polymer clay body. But it doesn’t dry out or get completely absorbed into the clay body, thereby assuring no adhesion. Also, the dampness of varnish abnormally reacts when it comes in contact with heat.

Nail polish

They are a colorful and good substitute for glossy, shiny, beautiful glazing. But the presence of chemicals can cause too much heat formation, which can burn out the clay. Also, it tends to get sticky, which is quite irritating.

7. Removing the clay out of the hot oven:

It is one of the biggest mistakes that beginners tend to make while baking clay. Removing the too hot clay from the oven right after baking will do nothing but result in the cracking of your pot. The sudden change in temperature can create a considerable amount of stress on the clay body, leading to cracking or breaking of the pottery piece. So, to avoid such situations, you should maintain some measures, as stated below.

8. Presence of trapped air bubbles in the clay:

While building the walls of your clay, be double sure that there are no air bubbles trapped in the way. The presence of air bubbles in the pottery wall makes the polymer much prone to cracking during baking.

To prevent trapping of air bubbles, put extra attention during the time of conditioning your clay. Giving the right conditioning to the polymer clay prevents air bubbles and also cracking or burning of the pot.


We have tried to cover the major reasons that lead to the breaking of your clay after baking. However, before working on your pottery project, it is always recommended to undergo several practice sessions to understand the facts and techniques of clay baking. Also, it is wise to always with smaller projects, especially if you’re a beginner. Experiment with your attempts to understand the temperature conditions of a particular type of clay and beat such baking-related problems.

However, it is not always the mistakes in your techniques, but also the quality of clay that has a great impact on how your pot behaves during and after baking. Hence, it is crucial to choose a superior quality clay to get the desired results. We hope the tips mentioned above will help you in understanding the baking process even better.

Happy sculpting!

Originally published at https://spinningpots.com on September 12, 2020.

Cat fanatic and Arts and Craft Lover. With Pottery being my favorite hobby. And a dangerous combo when you add in a couple of chaotic cats. :)