Can I Bake Air Dry Clay To Harden It?

What is Air Dry Clay?

Air dry clay, also known as cold porcelain, is a modeling and sculpting material made primarily from calcium sulfate dihydrate plaster (better known as plaster of Paris) and a non-toxic stabilizing binder or glue.

Unlike ceramic clay that requires firing in a kiln, air dry clay dries naturally at room temperature. The drying process takes 24-72 hours depending on factors like thickness and humidity. Once fully dried, air dry clay hardens into a durable, solid material similar to bisque-fired clay.

Key properties of air dry clay include:

• Smooth, doughy texture when wet
• Does not shrink or crack as it dries
• Lightweight, easy to sculpt and mold
• Paintable and sandable when dry
• Non-toxic and safe for kids

The main difference between air dry clay and ceramic clays like earthenware or stoneware is that air dry clay does not require firing in a high temperature kiln. It also does not need to be glazed or sealed for protection. Additionally, air dry clay cures at room temperature rather than through heat, making it more accessible for hobbyists, kids and beginners.

Can You Bake Air Dry Clay?

Yes, baking air dry clay is an effective way to harden it further. Though air dry clay will harden naturally at room temperature over time, baking provides a more thorough hardening and curing process. When baked, the clay undergoes a chemical reaction that converts the material into a hard, ceramic-like finish.

The recommended baking temperature for air dry clays is generally between 130°F (265°C) to 275°F (135°C), depending on the specific clay brand. Pre-conditioned clays like Original Sculpey can be baked at the lower end around 130°F, while clays like Crayola Air Dry Clay require closer to 275°F for proper hardening.

Baking times range from 10-15 minutes for thinner pieces, up to 1-2 hours for thicker sculptures. Closely follow the manufacturer’s recommendations for exact time and temperature. It’s important not to exceed the recommended baking temp, as too high heat can cause cracking or scorching. Allow pieces to fully cool before handling after baking.

Why Bake Air Dry Clay?

Baking air dry clay serves several important purposes that make the finished pieces more durable and usable. The main reasons to bake air dry clay are:

Makes it more durable and harder: Baking hardens and strengthens air dry clay, making the finished pieces less prone to cracking or chipping from normal use and handling. The clay becomes much denser and more stone-like after baking.

Strengthens it and prevents future cracking/chipping: Baking air dry clay helps seal and strengthen it by finishing the drying process. This prevents future cracking or deteriorating of details on the baked clay pieces.

Seals the clay against moisture: The baking process fully hardens the clay and seals the outer surface, which prevents moisture from being re-absorbed back into the clay. This protects all painted and unfinished surfaces.

How to Bake Air Dry Clay

Baking air dry clay is a simple process but there are some key steps to follow for best results:

1. Prepare the Clay

Before baking, ensure your air dry clay sculptures are 100% dry to the touch. Baking wet clay can cause cracks or explosions. Allow your clay to air dry for 24-48 hours. For larger pieces, dry even longer. Condition the clay by kneading it before baking to eliminate air pockets.

2. Preheat the Oven

Preheat your oven to the desired baking temperature, typically 275°F. Place your clay sculpture on a baking sheet or oven-safe dish. Avoid placing directly on the racks.

3. Bake at Low Temperature

Bake air dry clay at 225-275°F. Start at the lowest recommended temperature and gradually increase if needed. Baking at higher temperatures can cause burning, cracking, or scorching.

4. Bake for 30-60 Minutes

Bake most air dry clay pieces for 30-60 minutes. Thinner pieces may only need 15-30 minutes. Bake larger or thicker clay sculptures for up to 2 hours.

5. Cool Completely

Allow the clay to cool down fully in the oven with the door closed. Never remove hot baked clay from the oven—thermal shock can cause cracking. Cool for 30-60 minutes before handling.

6. Check for Doneness

The clay should be hard after baking. There should be no moist spots. Tap the clay gently—it should have a ceramic hollow sound, not a dull thud. Bake longer if needed.

Follow these baking instructions and tips, and your air dry clay creations will transform into strong, hardened pieces ready for display and play.

What Temperature to Bake Air Dry Clay?

When baking air dry clay, the recommended baking temperature is generally between 130°F to 275°F. The optimal temperature depends on the type of clay and the level of hardness you want to achieve.

Higher baking temperatures between 225°F and 275°F will result in a harder, more durable finished piece. Polymer-based clays like Sculpey and Fimo can be baked at 275°F. For other clay types, aim for lower temps closer to 200°F to prevent scorching and cracking.

Lower baking temperatures around 130°F to 190°F are suitable for clays that don’t require as much heat to harden and set, like air dry clay and homemade salt dough. Baking at a lower temperature helps prevent the clay from burning or becoming too brittle.

Always check the packaging or manufacturer instructions for the recommended baking temperature. Going too high can risk fires or burning the clay. Too low may not fully cure the clay. Finding the right baking temperature is key for properly hardening air dry clay in the oven.

How Long to Bake Air Dry Clay

When baking air dry clay, the baking time will depend on the type of clay you are using as well as the thickness of the clay pieces.

For most standard air dry clays, the baking time is typically 1-3 hours at 275°F. Thinner pieces made with 1/4″ clay can be baked for 1 hour while thicker pieces made with 1/2″ or more clay may need 2-3 hours to fully cure and harden.

Polymer-based clays specifically designed for baking, like Sculpey, usually have shorter baking times of 15 minutes up to 1 hour at 275°F. Again, the thickness of the pieces will determine baking time – bake thinner pieces for 15-30 minutes and thicker pieces for 45-60 minutes.

When determining if the clay is finished baking, check for these signs:

• The clay has firmed up and is completely hard and rigid
• The clay has lightly browned or discolored

Avoid underbaking the clay, which can result in pieces that are still soft, sticky or prone to cracking. If unsure if the full curing time was met, allowing the clay to bake slightly longer is recommended.

Can You Overbake Air Dry Clay?

Yes, it is possible to overbake air dry clay. When exposed to excessive heat for too long, air dry clay can become brittle, discolored, or even scorched. There are a few key signs that your clay has been overbaked:

Color Change – The clay will start to darken and change color the longer it bakes. Pale clays like white and beige will turn an amber color. Bright clays will fade and become dull.

Brittleness – Overbaked clay will be dry and fragile. It is prone to cracking, crumbling, or shattering when handled. The clay loses its flexibility and sturdiness.

Burning/Scorching – If severely overheated, the clay can start to burn or scorch. You’ll see black or brown burn marks on the clay. It will be irreversibly damaged.

The material properties of the clay change dramatically when overbaked. It is always recommended to closely monitor the clay in the oven, checking it frequently near the end of the advised baking time. This prevents accidentally overbaking your creation.

Storing and Handling Baked Clay

When your air dry clay sculptures are finished baking, make sure you store them properly to prevent damage. Here are some tips for storing baked clay:

Store pieces in a dry location away from moisture. Exposure to moisture can cause baked clay to soften and lose its structural integrity. Place pieces in a cabinet, on a shelf, or in an airtight plastic container.

Avoid stacking multiple baked clay pieces directly on top of each other, as this can cause chipping or cracking. If needed, layer pieces with cloth or bubble wrap between each item.

Prevent dust buildup by wiping pieces with a dry soft cloth periodically. Dust can collect in crevices and be difficult to remove.

Handle baked clay carefully, as it can chip or crack if dropped. Move pieces gently and avoid placing heavy objects on top that could cause impressions or scratches.

Baked air dry clay has a hard, durable finish that will last for years with proper care and handling. Be mindful of potential cracks or weak points that may need glue repairs. With some simple storage methods and care, your polymer clay creations will remain beautiful works of art.

Troubleshooting Baking Clay

Baking clay can sometimes lead to issues like cracking or scorching if not done properly. Here are some common problems and how to avoid them:

Cracking

Cracking happens when the clay dries too quickly or there is too much moisture present. To prevent cracking:

• Allow clay to air dry completely before baking
• Avoid baking clay that is thicker than 1/4 inch
• Bake at a low temperature first to draw out moisture slowly

Scorching

Scorching occurs when the clay is baked at too high of a temperature. To avoid scorching:

• Follow recommended baking temperatures
• Avoid exceeding the baking time
• Use an oven thermometer to ensure accuracy

With proper air drying, pre-heating, and following the temperature guidelines, you can avoid most baking issues with clay. Take your time and bake slowly.

Alternative Ways to Harden Clay

While baking is the most popular and effective way to permanently harden air dry clay, there are other options if you don’t have access to an oven:

Air Drying: You can harden air dry clay simply by leaving it to dry in the open air. This takes 1-3 days depending on the thickness and ambient conditions. Air drying is free and doesn’t require any special equipment. However, it results in a more fragile piece compared to baking, and has a risk of cracking or warping as the clay dries.

Oven Drying: You can harden air dry clay in a low temperature oven (200°F or less) for 1-2 hours. This dries the clay thoroughly without baking it. It still won’t be as hard or durable as true baking, but helps reduce cracking and warping issues. Just watch closely to prevent any scorching.

Microwave: You can quickly harden thin pieces of air dry clay in the microwave for 1-2 minutes per side. This can cause bubbling or cracking so it’s not recommended for large or complex pieces. Results are not as hard as baking but faster than air drying.

Varnish/Sealant: Applying a varnish, mod podge, or sealant can help harden and strengthen air dried clay slightly. It provides a protective coating and prevents moisture absorption. But it’s primarily just a surface treatment and does not permanently harden clay throughout like baking does.

So in summary, baking clay in a proper oven at the right temperature ultimately provides the most hardness, durability and permanent results. But for non-baked options, air drying, oven drying and quick microwaving can also harden clay to varying degrees.