Grades 3–5 · Arts & Music
How does a ceramic cup get its smooth glazed surface?
Some fired clay still contains tiny connected spaces that can take in water. A ceramic cup may have an additional smooth layer called a glaze. That coating has a different structure from the clay body beneath it.
In the diagramA glassy coating can bridge ceramic surface poresglassy glaze layerporous ceramic bodyEnlarged layers; appearance cannot establish food safety.
Before firing, glaze materials are applied as a coating containing fine particles. In the kiln, the mixture softens or melts sufficiently to spread and join into a glassy layer. Its ingredients and firing conditions determine how it behaves.
As the cup cools, the glaze becomes a solid surface bonded to the clay. A suitable continuous coating can reduce the passage of water through surface pores. It can also provide color, shine or a particular texture.
Glazing and making the clay body strong are related but different jobs. A glaze must fit its underlying ceramic as both cool. Cracks, incomplete coverage or unsuitable ingredients can affect the result, so appearance alone does not establish a cup’s properties.
About this explanation
Starting knowledge: Know that clay objects are fired in a kiln and that a porous material contains small spaces.
Sources
- Victoria and Albert Museum — An A–Z of Ceramics