Glaze is a thin, glass-like layer that's melted onto ceramics during firing. It makes porous clay dense and water-resistant, protects the surface and gives the ceramic its glossy or matte look. Most glazes on tableware are food-safe, and you look after them best by avoiding abrasive cleaners and rough sponges.
Contents
When you hold a smooth, glossy ceramic vase or a cup up to the light, it's the glaze you're seeing and feeling. Glaze is one of the main reasons ceramics can be used for both flowers, food and drink. In this guide, we take a look at what glaze actually is, why it's used, and how you keep your glazed ceramics looking beautiful for years to come.
What is glaze?
Glaze is basically a type of glass powder that's applied to the raw or bisque-fired clay and then melted onto it in the kiln at high temperature. During firing, the glaze's components melt together into a thin, hard, glass-like layer that bonds to the surface of the clay. The result is an even, often glossy surface that you can both see and feel.
Glaze is typically made up of three types of ingredients: a glass-forming material, a substance that lowers the melting point, and a hardening material that binds it all together. Colour and appearance are controlled by added minerals and metal oxides, which is why glazes can range from deep, glossy colours to calm, matte shades.
Why is glaze used?
Glaze has both a practical and an aesthetic function. Clay is in itself more or less porous, and the glaze seals the surface so the ceramic becomes dense and easier to use in everyday life.
- Density: The glaze makes porous clay water-resistant, so water and liquid don't seep into the material.
- Durability: The hard layer protects the surface against scratches, wear and stains.
- Hygiene: A smooth, dense surface is easier to clean and picks up less dirt than an open, porous surface.
- Look: The glaze provides colour, shine and depth and is a big part of the ceramic's visual character.
Tip: If the base of a vase or bowl is unglazed, it can scratch your table. You might want to add a small felt pad or a napkin underneath to protect both your furniture and the ceramic.
Glossy, matte and unglazed
Glaze comes in many different looks. The most common distinction is between glossy and matte glazes, as well as completely unglazed ceramics, where the clay is left raw. Each type has its own advantages.
| Type | Look | Properties |
|---|---|---|
| Glossy glaze | Shiny, reflects light | Dense, easy to clean, brings out colours |
| Matte glaze | Muted, soft surface | Calm look, can be more prone to showing grease and fingerprints |
| Unglazed | Raw, natural clay | More porous, can absorb liquid and stains more easily |
Is glaze food-safe?
Most glazes used on tableware such as cups, plates and bowls are made to be food-safe when fired correctly. A well-fired, dense glaze doesn't release substances into food and drink during normal use.
However, do take care if you have decorative ceramics, craft pieces or older items where you don't know the glaze. In these cases, you should follow any instructions from the manufacturer and only use ceramics for food if they're intended for that purpose. If in doubt, use the item decoratively rather than for serving.
Crazing
Crazing is the fine network of small cracks that sometimes appears in the glaze. This is typically caused by the glaze and the clay expanding and contracting at slightly different rates as the ceramic heats up and cools down.
Crazing can be a completely intentional, decorative effect, and many people appreciate the lively, handmade look it gives. On tableware, though, the cracks can gradually collect liquid and become discoloured over time. So use crazed ceramics thoughtfully for food, and dry them thoroughly after use.
Caring for glazed ceramics
Glazed ceramics are fairly easy to look after, but a few simple habits will help them last longer and keep their shine.
- As a rule, wash by hand with a soft sponge and ordinary washing-up liquid.
- Avoid abrasive cleaners, steel wool and harsh scouring pads, as these can scratch the glaze.
- Rinse well so no soap residue is left behind.
- Dry the ceramics off, and let them air-dry completely before putting them away.
- Avoid sudden changes in temperature, which can stress both the clay and the glaze.
Tip: Got brown coffee or tea stains in a glazed cup? A soft paste of bicarbonate of soda and a little water often removes the discolouration gently without scratching the glaze.
Frequently asked questions
What is glaze made of?
Glaze is a type of glass powder consisting of a glass-forming material, a substance that lowers the melting point, and a binding material. Minerals and metal oxides give colour and character.
Why is ceramic glazed?
Glaze seals the porous clay, making the ceramics dense and water-repellent, more durable and easier to clean. At the same time, it adds colour and shine.
Is glazed ceramic food-safe?
Most glazes on tableware are made to be food-safe when properly fired. For unknown or decorative ceramics, you should follow the manufacturer's instructions.
What is crazing?
Crazing is fine cracks in the glaze that occur when the glaze and clay expand differently. It can be a deliberate decorative effect, but it can collect liquid on tableware.
What's the best way to clean glazed ceramics?
Wash by hand with a soft sponge and mild washing-up liquid, avoid abrasive cleaners and harsh sponges, rinse well and let the ceramics dry completely before putting them away.
Summary
Glaze is the glass-like layer that's melted onto ceramics, making them dense, durable and beautiful. It comes in glossy, matte and completely unglazed finishes, and most glazes on tableware are food-safe. Take care of your ceramics by washing them gently, avoiding abrasive cleaners and drying them thoroughly, and the glaze will keep its shine for many years.
