How to Harden Clay After Casting

Play clay comes in many varieties, including ppymer clay and self-drying clay, often used to make interesting products such as dishes, jewelry, and other crafts. You can easily perfect your creation by heating the ppymer clay in the oven or allowing the clay to dry on its own.

Table of Contents

Heating ppymer clay

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Use a needle to make an air hole if your model has an airbag. For models with air pockets on the inside, you need to create an air hole to prevent cracking due to temperature changes in the oven. Insert a needle into the model until it penetrates the internal airbag. ^{[1] X Research Source}

If there are no air bags in the model, you don’t have to worry about creating air vents!
Make sure to fill each airbag with at least 1 hole to let all the air out.
For example, many animal models are hollow inside for lightness. In addition, jewelry such as earrings can have air pockets, especially delicate items.

Note, some clays such as oil-based clay are not designed to harden, so check the packaging of the clay product you are using to be sure!

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Read the instructions on the package for the firing temperature. Most modeling clay products have an instruction manual stating the firing temperature, which is usually between 100 – 150 degrees Celsius. Check the packaging to see if the firing temperature varies with the thickness of the model. no, then preheat the oven to that temperature. ^{[2] X Research Source}

If using more than one brand of clay in the same model, follow the instructions for the clay that makes up the majority of it. If you are unsure, you can set the temperature to about 129 degrees Celsius.

Place the clay model on a ceramic baking tray. While you wait for the oven to heat up, place the clay model on a piece of oven-safe ceramic. You can use a ceramic baking dish, or even a ceramic tile. ^{[3] X Research Sources}

Ceramic material retains heat well and can prevent sudden temperature changes when you open the oven door.
Avoid metal or glass trays, as these materials are prone to temperature changes.

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Fire the clay model immediately after painting or glazing. One of the advantages of ppymer clay is that you don’t have to let the paint dry before firing. As soon as you finish the model with 1-2 coats of paint, open the oven to prepare it for firing.

Painted or enameled models will require a little longer firing. Normally, each layer of paint or enamel will need to be fired for another 3-5 minutes.

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Heat the clay according to the time instructions on the package. Most clay brands have a firing time of about 10-30 minutes, depending on the thickness and color of the clay. A general rule of thumb is to bake for the time indicated on the package for each 0.65 cm of thickness. ^{[4] X Research Sources}

For example, if your model is 1.3 cm thick and the instructions on the package are to bake for 15 minutes, you will have to bake for 30 minutes.
If the packaging can no longer be kept, it is recommended that you heat it at a lower temperature for a longer time (eg 30-40 minutes) just to be safe.

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Prepare a pot of ice water while heating the clay. Choose a large pot or bucket that fits the model. Pour ice water up to 5cm from the pot to leave room for the water to rise.

The model needs to be completely submerged in water, so you should use the largest pot possible.

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Remove the model from the oven and immerse it in the water immediately. When the firing time is up, use a shovel to remove the model from the ceramic tray. Carefully transfer the model to the pot of ice water and soak for at least 30 minutes so the clay doesn’t overheat. Use your hands or tongs to remove the model after soaking for enough time.

When fresh out of the oven, the model may still be a little soft on the outside, so some tools like tongs can leave indentations on the hot clay surface. You should only use tongs when removing the model from the ice, not when placing it in the immersion.
If you don’t know how to submerge the model in ice, just put the ceramic tray in the water.

Self-drying clay

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Hong model clay for 24-48 hours to dry. Keep the model in a dry, well-ventilated place and do not touch it. Every 4-6 hours check it for cracks or chipping, and make sure it’s hardening. Drying time will vary depending on the thickness of the model and the humidity in the air, but most self-drying clay products will dry completely within 72 hours. ^{[5] X Research Sources}

If your model doesn’t harden after about 12 hours, try increasing the temperature by blowing the model with a hair dryer or putting it in the oven on the lowest setting for 1-2 hours. Remember to check in from time to time.

Treat cracks that appear during drying. As the clay begins to dry, you may notice some cracks or dents appearing on the model that were not there before. To smoothen cracks, dip your finger in clean water and smooth over the imperfections a few times. ^{[6] X Research Source}

If large cracks form during the drying process, you may have to redo the model by kneading the clay again. Pour a little water into the clay and put it in a plastic bag for about 10 minutes, then take it out and knead again, continue to add a small amount of water until it is flexible enough to mold.

Advice

When firing clay, you should try to avoid opening the oven door to allow heat to escape or the model to crack due to sudden temperature changes.
Please be patient! Some clay products can take 72 hours to dry completely. Your item may be damaged if you touch it or move it away before this time.

Steps

Heating ppymer clay

Self-drying clay

Advice

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