Air dry clay, and the three things every buyer asks about it

Printed prices, verified

Four questions that decide whether air dry clay is the right buy

1. Will the finished thing ever hold water or food?. If yes, air dry clay is the wrong material and no sealant changes that honestly. A dried air-dry body softens when it is soaked and has no glaze layer fused to it. A fired stoneware, priced from about a pound a kilogram on this index, is the material that does that job.
2. How thick is the thickest part?. Air dry bodies shrink as they dry and crack where a thick section pulls against a thin one, exactly as fired clay does in the greenware stage, but with no firing to consolidate it afterwards. Build hollow, keep walls even, and slow the drying with a loose plastic sheet for the first day.
3. What are you painting it with?. Acrylic is what almost everyone uses and it is what most manufacturers name on their own packaging. It goes on after the body is dry all the way through, not while it is damp, and a varnish over the top is decoration and water resistance rather than waterproofing.
4. How much are you buying?. Air dry clay is sold in small packs at craft prices and in bags at supplier prices. If you are equipping a class, the suppliers indexed here sell it by the bag beside their fired bodies, and the per-kilogram difference is large.

What air dry clay is, next to what fired clay is

A fired stoneware goes into a kiln at around 1200 degrees and comes out a different material: the particles fuse, the body vitrifies, and a glaze fired with it becomes glass bonded to that surface. That is what makes a mug a mug. Air dry clay never has that event. It dries, the binder holds the particles together, and the object is as strong as the binder rather than as strong as ceramic.

The practical line is water. Anything that will be washed, filled, planted into and watered, or left outside through a winter, wants a fired body. Anything decorative, modelled, painted or made by a child in an afternoon is what air dry clay exists for, and for that job it is better than the alternative because it needs no equipment at all.

Drying, cracking and the one thing that fixes most of it

Most air dry clay failures are drying failures and most drying failures are speed. A thin edge dries and shrinks while a thick centre is still wet and full size, and the join between them tears. The fix is not a product, it is patience and even thickness: hollow out anything thicker than about two centimetres, and cover the piece loosely for the first twenty-four hours so the surface does not race ahead of the core.

A crack that appears while the piece is still damp can be filled with slip made from the same clay and a little water. A crack that appears after it is dry can be filled but not healed, because there is no firing to fuse the repair.

Silica, dust and the part nobody puts on the packet

Air dry clay is wet in the bag and safe to handle. The hazard on this shelf is dry material: sanding a dried piece, sweeping a dried floor, or handling powdered clay all put respirable crystalline silica into the air, and that is the same dust that the fired-clay side of this hobby manages carefully.

Sand wet rather than dry, wipe surfaces down instead of brushing them, and keep powdered material in its bag until it goes into water. None of that costs anything, and it is the only health advice this page gives, because it is the only one that applies to a material sold to schools.

Common questions

How long does air dry clay take to dry?

Between one and three days for a small thin piece and up to a week for something thick, at ordinary room temperature. It is dry when it has stopped feeling cool to the back of your hand, because the coolness is water evaporating.

Can you bake air dry clay to speed it up?

An oven drives water out of the surface faster than it can leave the core, which is exactly the condition that cracks a piece. If you must speed it up, use moving air rather than heat: a fan in the room does more good than an oven and does no harm.

Can you make air dry clay waterproof?

You can make it water resistant with a varnish or a resin, well enough for a plant pot liner or an ornament that gets damp. You cannot make it hold water like a fired glazed pot, and any product promising that is describing a coating rather than the clay.

Is air dry clay the same as modelling clay?

No. Modelling clay in the plasticine sense never hardens at all, which is what makes it reusable. Air dry clay hardens once and stays hard.

Browse by material

• Compare Stoneware clay on printed prices
• Compare Earthenware and terracotta clay on printed prices