Firing

after the clay is dried, it is fired to chemically change its structure, making it stronger, more durable unaffected by water and harder wearing.

firing can be done to a large number of temepratures, with each temperature affecting each clay body and glaze differently, and can help acheive the desired end product.

as clay is raised to higher and higher temepratures, it generally shrinks in size, both due to loss in moisture but also into various compounds melting and fusing together in the body. this is accompanied with a decrease in porosity, making the the wares absorb less water, as well as a general increase in strength. Firing too high can have adverse affects - pieces can become brittle and fragile again if fired too hot. Even hotter and they may melt and slump into puddles of glass.

although pieces genrally shrink throughout the drying and firing process, some swelling can occur at the quartz inversion stage (550˚-600˚). Care must be taken to not pack the kiln too tight to stop wares from sticking to eachother through this swell in size.

Bisque Firing

Bisque firing is the process of firing ceramics up to aprox. 1000˚, but can depends on the specifics of the clay and its desired application. This firing partially vitrifies the clay, chemically changing its composition so that it is no longer affected by water, though this does not mean it is not porous and will not absorb water. It will also be stronger than dried clay, making it less delicate to handle.

Bisque Firing is mostly done to prepare the work for glazing. The increase in strength makes them less delicate to handle while applying glazes, and the fired nature of the clay means that organic matter is burned off and moisture has been evaporated, both of which can cause unwanted effects when interacting with glazzes.

Compared to higher temperature firings, Bisque ware is more porous, which helps the glazes soak into the clay body - greatly increasing the strength and joint of the glaze to the clay. However this also means Bisque ware is not watertight - a bisque fired vase of water will weep water through its body.

Glaze Firing

Glaze Firings are done at a variety of temperatures (1100˚-1220˚) depending on the clay body and glaze. This second firing converts the dried glaze on the bisque fired body into a glasslike surface. It also has the effect of decreasing porosity, making the works stronger, and more impervious to water.

Higher Firings

Pieces can be fired past 1220˚, which can increase their strength, and also affect the colour of the clay body in interesting ways, however most glazes are not suited to these temperatures- they will degrade, burn and potentially run off the pieces.