A ceramic glaze is a thin layer of glass fused to the surface of a pot during firing. It seals porous bodies so they hold liquid, protects the surface, and carries colour and texture. Raw glaze is a suspension of finely ground minerals in water; in the kiln those minerals melt and fuse to the clay. Because it becomes glass, glaze is what turns a porous fired body into functional, washable ware.

The rule that matters most: match the cone

Before anything about colour or finish: a glaze is formulated to melt and mature at a particular cone, and it must be fired to the cone your clay body is fired to. A cone 6 glaze on a cone 6 stoneware, fired to cone 6, works. The same glaze fired too cool will be underfired and rough or unsealed; fired too hot it can run off the pot onto your kiln shelf. Read the cone rating on every glaze and pair it to your clay and firing. Get this right and most beginner glaze problems disappear.

Common glaze types by surface

Transparent / clear

A glassy, see-through coat. Used alone over a clay or slip you want to show, or over underglaze decoration to seal and brighten it.

Opaque, glossy and matte

Opaque glazes hide the body beneath. Within that, glossy glazes give a shiny, reflective surface while matte glazes give a soft, non-reflective one. The same colour can read very differently glossy versus matte.

Coloured and specialty glazes

Colour comes from metal oxides and stains in the glaze. Beyond plain colour, specialty glazes — such as flowing, broken-surface or crystalline effects — create more complex results, and are best approached once you are comfortable with basics, since they behave less predictably.

How glaze is applied

Glaze is normally applied to bisque ware — pottery that has had a first, lower firing to harden it while keeping it porous enough to absorb glaze. The main methods:

Dipping

The pot is dipped into a bucket of glaze for an even, fast coat. Efficient and consistent, but needs enough glaze to submerge the piece.

Pouring

Glaze is poured over and through the pot. Good for insides of vessels and for larger pieces that won't fit a bucket.

Brushing

Glaze is painted on in several coats. The most accessible method for beginners and for small batches, and the usual way to apply brushing glazes sold for the purpose; it takes more coats to build an even layer.

Spraying

Glaze is sprayed on for fine, even gradients. It needs a spray booth and equipment, so it is a later step rather than a starting point.

Food safety and finishing

If you make tableware, use glazes labelled food-safe and fire them correctly to their rated cone — proper maturation matters for a durable, stable surface. Keep glaze off the foot of the pot and off kiln shelves, since melted glaze fuses to whatever it touches. When unsure whether a particular glaze is safe on surfaces that touch food, follow the manufacturer's guidance.

Related reading

To match glaze cone to clay, see clay types. To make sure your kiln reaches the glaze cone, see how to choose a home kiln.

Sources & further reading