What is glaze, and how does it work?

Glaze is a thin, glass-like coating applied to pottery that, when fired at high heat, melts into a smooth, hard surface. Glazing is what gives a finished ceramic its colour, its shine (or matte finish) and — importantly — a waterproof, food-safe surface. It is usually the final step before a piece is complete.

The two firings: bisque vs. glaze

Most pottery is fired twice. The first firing, called the bisque firing, hardens the raw clay into a porous, durable state called “bisqueware”. Glaze is then applied to the bisqueware, and the piece goes back into the kiln for a second, hotter glaze firing. That final firing melts the glaze into glass and locks in the colour and finish.

Types of ceramic finishes

  • Glossy glaze: a shiny, reflective, glass-like surface — the most common finish.
  • Matte glaze: a soft, non-reflective surface.
  • Coloured glaze: pigments in the glaze produce blues, greens and the rich tones seen in Moroccan ceramics.
  • Clear glaze: transparent, used to seal and protect painted decoration underneath.

Glazing vs. painting: what’s the difference?

Painting decorates the surface with ceramic paints and is often the creative, hands-on part you do in a workshop. Glazing is the technical coating that seals the piece and gives it a durable, waterproof finish in the kiln. On many decorated pieces, you paint your design first and a clear glaze is applied over it to protect it. Painting is about the design; glazing is about the finish and protection.

A note on food-safe pieces

A ceramic is only food- and drink-safe when it is coated in a food-safe glaze and properly kiln-fired. Decorative pieces painted with standard acrylics are beautiful but not intended for eating or drinking. If you want to use your piece for food, ask your studio about food-safe glazing and firing.

See Moroccan glazing in Marrakech

Moroccan ceramics are famous for their deep blues, greens and geometric glazework. You can see and try glazing in our pottery class, or focus on hand-painting your own design in our ceramic painting workshop.

Key takeaways

  • Glaze is a glass-like coating that colours, seals and waterproofs pottery.
  • Pottery is usually fired twice: a bisque firing, then a glaze firing.
  • Finishes include glossy, matte, coloured and clear glazes.
  • Painting is the design; glazing is the protective, food-safe finish.

FAQ

What's the difference between glazing and painting pottery?

Painting decorates the surface with ceramic paints; glazing applies a glass-like coating that's fired in a kiln to seal the piece and give it a durable, often waterproof finish.

Is painted pottery waterproof?

Only if it's sealed with a food-safe glaze and kiln-fired. Pieces decorated with standard acrylic paint are decorative rather than watertight or food-safe.

Why is pottery fired twice?

The first (bisque) firing hardens the clay so it can be handled and glazed; the second (glaze) firing melts the glaze into a smooth, permanent finish.