How to Avoid Cracks When Baking Polymer Clay

Cracks will destroy the look of your clay creation, disfigure your designs and harm your project’s durability. They can appear as large fissures that spread over most of your piece, or they can show up as small fine cracks that appear on the surface of the clay. To prevent these cracks from forming, you need to know the best practices for baking polymer clay without cracking.

Learn more about how you can protect your baked polymer clay from cracking and various tips for proper baking.

Steps to Baking Polymer Clay Without Cracking

Keeping your polymer clay from cracking isn’t all that complicated. With a few straightforward practices, you can make cracked clay a thing of the past. Below, you can learn more about the steps to prevent your baked polymer clay from cracking in the oven.

1. Fully Condition Your Clay

Unconditioned clay has a much higher chance of cracking when you put it in the oven and expose it to high temperatures. Due to the impact of not thoroughly conditioning your clay, you should make sure to completely condition your clay before placing it in the oven.

Conditioning involves kneading and warming polymer clay to get it ready for use. You can complete the conditioning process manually or through a clay conditioning machine. The amount of curing time required will depend on the thickness of the clay and the brand of clay. 

2. Check for Air Bubbles 

After conditioning the clay, you should check it for trapped air bubbles that can cause cracks. Since these air bubbles often form in the conditioning process, you must take steps to prevent them from appearing.

One step you can take to prevent bubbles is to tear your clay instead of folding to prevent the clay from trapping air. If you see any bubbles forming while you condition it, pop or cut them immediately, as they can hide in the clay when left unchecked. You can also stretch or pull on your sheet of clay to release air in the material.

3. Maintain a Consistent Temperature 

Once you place your clay in the oven, maintain a constant temperature to prevent cracks from forming. Many countertop ovens lack proper seals that ensure a consistent temperature. The absence of seals can cause your oven’s temperature to swing wildly, with your oven’s temperature dipping down and then spiking up. These temperature fluctuations can lead to an uneven bake and cracked clay.

To make sure your oven maintains a consistent temperature, you can purchase an oven thermometer. This thermometer will give you a more accurate reading than your display and show if you can trust your oven to bake clay correctly.

Besides keeping your oven at a consistent temperature, you should make sure you aren’t baking your clay over the recommended temperature, as it could cause the clay to burn. It could also burn if you place the clay too close to the oven’s heating elements. Put the clay in the center of the oven to prevent it from interacting too closely with the heat.

Baking Polymer Clay Tips and Tricks

Besides the steps listed above for preventing cracks while baking polymer clay, there are a few other pieces of information that can help you bake your polymer properly. You may not know the temperature or the time required for baking clay, so it’s crucial to learn how to ensure your clay comes out correctly. 

Below are some common questions crafters usually have about baking polymer clay.

  • What temperature should I bake clay? There’s not a set temperature for all the different clays available on the market today. You should always stick to the temperature the packaging states. Manufacturers will specially formulate their clays, so it’s critical to stick to their specifications. Not doing so could lead to clay cracking or burning.
  • Will a higher temperature make my project bake faster? To avoid burning, never bake your clay projects at a higher temperature than the clay’s packaging suggests. A higher temperature will also lead the polymer clay to break down and degrade. 
  • How long should you bake polymer clay? You should follow the instructions on the clay’s packaging to see how long to bake it. Like the oven temperature, the time will depend on a company’s clay formulation and thickness of your creation, so it’s crucial you stick to the packaging’s specifications.
  • Can I bake my clay in a microwave? Don’t try to use a microwave to bake your clay. It’s difficult to set temperatures in microwaves, and they also have hot spots. If you put your clay in your microwave, it can end up experiencing a thermal breakdown, which could lead to fumes and charring.
  • What should I put my clay on? When you’re baking your clay, place it on a metal sheet, oven-proof glass, ceramic tile, index card, aluminum foil or the Sculpey Oven-Safe Work Mat.
  • Do you have to bake polymer clay? Yes, you must bake polymer clay. This material isn’t suitable for air drying and won’t fully cure if you never bake it. Baking your polymer clay ensures proper curing and prevent cracking.
  • What if I am baking two brands of polymer clay? When baking multiple clay brands, always bake at the higher temperature and for the longer time of the two.

Repairing Polymer Clay

If you follow the steps above you should be able to prevent your polymer clay from cracking. However, both breaking and cracking can occur when the clay is not baked or cured properly.

Cracking is almost always caused by insufficient curing or by baking a sculpture with uneven thicknesses throughout. To ensure you have a consistent thickness in your piece, we recommend “bulking out” with foil or creating an armature from Super Sculpey UltraLight™. It is also very important to adhere to proper baking times and temperatures. Using an oven thermometer is the most accurate way to make sure your oven is heated to the exact temperature.

When your sculpture does crack or break, there are several ways to repair the polymer clay. Read on to discover ways you can fix broken clay creations — and even prevent them in the first place! 

How to Fix Broken Polymer Clay Pieces

While it is tempting to add new clay to your creations and rebake them, this may not have the desired results — cured and uncured clays will not meld with each other. In fact, trying to fill cracks with new clay often causes them to widen. 

If your piece has suffered a break, you may be able to save your clay project with some carefully placed glue and a paint touch-up. 

How to Fix Cracks in Polymer Clay: Adding Clay Dust to Hardened Pieces 

Cracks in the surface of a project can be frustrating, but there are some no-bake ways to save your finish. If the completed piece is destined for paint, mix some two-part plumber’s putty and spread it smoothly into the cracks. This epoxy will air-harden in just a few minutes, and you can sand and paint the repaired piece once it’s fully set. 

Already happy with your Sculpey® color? Take a small piece of baked clay in the same shade and use a rasp or grater to make clay “sawdust.” Then, mix your colored dust with a clear, air-hardening epoxy glue and fill the cracks. 

How to Prevent Polymer Clay From Breaking or Cracking 

Variation in thickness is one of the most common reasons clay experiences cracks or breakage. To ensure you maintain sufficient compactness so the piece can cure properly, try:

  • Creating an armature from Sculpey® UltraLight™ or adding crushed aluminum foil as bulk to keep the clay layer consistent. 
  • Using an oven thermometer to make sure your home oven is heated to the recommended temperature. 
  • Ensuring baked pieces of polymer clay are not exposed to significant humidity or temperature changes.
  • Working in some Sculpey® Clay Softener before baking if you are working with a very thin clay layer — the increased flexibility will help keep it stable.
  • Using a type of support under the polymer clay piece before placing it in the oven to bake. Extended or raised portions of the clay can sag or crack when heated. Supports you can use under the clay to keep it in place during baking include crumpled aluminum foil, crumpled up tissue paper or paper towels, glass bowls, fiberfill, wire supports or wooden dowels. 

Choose High-Quality Polymer Clay From Sculpey

Now that you know how to bake polymer clay so it doesn’t crack, you should be ready to purchase high-quality polymer clay for your next project. Sculpey is proud to provide crafters, no matter their skill level or age, with the best polymer clay on the market. We offer numerous color palettes, and our clays feature incredible strength and flexibility. Besides our top-quality clays, we also offer many polymer clay tools to work with the material and bring your vision to life. 

Browse our clay products to find the best kind for your next creation. If you have any questions, contact us, and one of our representatives will be happy to help. 

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