We often get questions about sealing and waterproofing ceramics. First, if you are firing porcelain or stoneware, read our tip about vitrification of clay. Your best means of achieving a waterproof piece is to fire your clay body to the right temperature. … Low-fire clay also is not waterproof.

What happens when fired clay gets wet?

As it dries out further it eventually becomes bone dry. It’s never a good idea to put wet or leather hard clay in the kiln. Even if you do pre-heat the kiln before firing, there will be too much moisture in the clay. Also, if you try to speed dry wet clay, it will most likely crack.

Is kiln dried clay waterproof?

While it’s not possible to glaze air dry clay in the traditional way using a kiln you can use varnishes and sealants to create a glazed pottery effect. Unlike traditional clay, air dry doesn’t need to be fired to set hard. … So while it’s not possible to truly waterproof air dry clay you can make it water-resistant.