Why is my earthenware glaze crazing?

The glaze may not be suitable for the particular clay. Clays and glazes expand and contract at different rates so it is important to choose a glaze that is suitable for your clay. All our glazes state which clay bodies they are suitable for. Crazing can also be caused by glazing over an underfired bisque, so it is worth checking the temperature of your bisque firing. Some glazes are designed to craze - check the label!