Cracking is normal in air dry clays: it's caused by shrinkage because of the loss of the water inside the clay body. Cracking in air dry clay is typically caused by sculpting over an armature or using a lot of water, either to mix the clay or to help it adhere onto a previous layer.
In order to dry properly, air dry clay projects should be exposed to air on all sides at the same time. This will help prevent warping and cracking. We recommend drying pieces on a screen or cookie rack, for example, where air flow is the same on all sides.
Clay has a memory. So in an effort to erase the memory of a crack, score the area in question deeper and larger than the crack itself (2), then place a bit of scored soft clay into the space you've made and compress it with a rib (3, 4). This will heal a crack in most cases, depending on how dry the cracked clay is.
Our Verdict. If you are in need of a versatile air dry clay that is non-toxic and suitable for all ages, the DAS Air-Hardening clay is crack-resistant, dries in 24 hours, and comes in white and terra cotta.
Air-dry clay usually takes 24-48 hours to dry completely.
However, it is best to check on the clay periodically to be sure. If you're looking for a quicker option, you may consider modeling clay that will dry in less than 24h. Baking air dry clay can cause it to warp or crack.
What is the best sealant for air dry clay? The best option to provide a water-resistant, durable seal on air dry clay objects is to use a polyurethane or acrylic sealer. These provide a durable, water-resistant finish to protect the air dry clay and prevent it from yellowing.
In general, cracks result from stresses in the clay. There is always some stress in clay because of the fact that it shrinks as it dries and when it is fired, and it also expands and contracts during firing. Sometimes the stress is too much for the clay to handle and it cracks.
Coat it with primer
Even when dry, the air-dry clay remains prone to dents and scratches. To strengthen its surface, coat it with a few layers of primer. It works wonders forming a smooth and sturdy exterior. Unfortunately, most good-quality primers come in grey color, so it can be harder to paint the surface later.
Can You Paint Air-Dry Clay Before it Dries? No, you need to wait for the clay to fully dry before you begin painting. By painting the clay while it is still wet, you run the risk of altering the clay item and causing cracks. However, you can color or dye the clay with paint before it dries by kneading in the paint.
A con to building with air dry clay is how fragile it can be. Thin additions like legs, fingers, and ears will easily break off. To avoid small parts breaking off, have students create mixed media pieces.
They harden within a few days and do not need to be fired to create a permanent form. Air-dry clay vessels and sculptures are more fragile than traditional kiln-fired ceramics, but they can be sealed and strengthened with shellac and paint.
It can be hardened simply by leaving it out in the air which makes it a popular choice for beginner crafters and families with kids. When the clay is fully dry it becomes hard and durable.
Sago Brothers modeling clay is very soft and smooth, no odor, doesn't crack, fade, or lose shape.
It's important to store your clay in a comfortable room temperature location. Your clay can freeze if it gets too cold or can melt if it gets too hot. So keeping your extra stash of clay in a dark cool environment, is ideal.
Adding too much water to your DIY air dry clay can sometimes result in a crack. Do your best to keep the clay moist as you work, but not overly saturated with water. If you have too much water, I recommend setting your clay out to dry for an hour or two before continuing on.
Mod Podge on Air Dry Clay
It's really easy to use Mod Podge and clay together (including polymer and air dry). Mod Podge is a great sealer for clay, which is what makes it so perfect for these charms/gift tags.
Depending on the thickness of your project, air dry clay will dry to earthenware hardness in around 24 hours. If you want to work on your piece in multiple sessions, wrap it in a damp tea towel and then cover it with cling wrap to make it air tight. This should keep it workable for around 4 days.
Air drying clay should be painted before being sealed. If you seal air dry clay before decorating you will be unable to paint your work, it will be 'sealed' against moisture, including your paints.
Water can be added to Air-Dry Clay to soften or join pieces. If too much water is added and clay is very soft, allow excess to evaporate before molding pieces; otherwise, cracking may result. Check frequently to determine when the clay achieves the desired workability.
Vinegar is also used in clay bodies to increase acidity to improve plasticity. The acid works to neutralize sodium ions (from water, leaching feldspars) that tend to deflocculate the clay. Excessive acid may tend to dissolve more feldspar or nepheline syenite negating the effect.
Storing Water-Based Air Dry Clay
Once dry, they cannot be re-hydrated and used any more. Some dried air dry clays will disintegrated if left soaking in water for a long time, but I would warn against trying this method to "revive" your clay.
You can seal your painted air-dry clay using a spray-on acrylic sealer. Resin is also an option but you can also find acrylic paints that carry their own sealant properties.