Bisquing
The Bisque process hardens the ware making it easier to handle without breaking during the glazing process. Clay fired at this temperature still retains its porosity, however. The porosity of a material refers to its ability to absorb a liquid. The liquid part of glaze, in this case water, is absorbed by the porous bisque ware, and the glassy materials in the glaze are left deposited on the surface of the bisque ware. So, the bisque process is typically done to make glazing easier.
The bisque firing can take a total of 3 days from start to finish. On day one, the kiln is loaded with the dry greenware and the kiln is preheated, set at a low setting to dry the ware, and left overnight to slowly warm. Firing too fast during this early stage of the firing can easily cause the work to explode. On day two, the kiln is gradually turned higher and the temperature rises until the target temperature of around 1800°F. is reached. The kiln is then turned off and allowed to slowly cool. On day three, the kiln is opened, the bisque ware removed and the cycle repeats.
Challenges
Many people think the bisque schedule is the easy part of the ceramic process but in reality many important changes occur in the clay during this firing. During the bisque firing you remove all existing chemically bonded water form the clay, you burn out any organic material, and the clay goes through whats known as quartz inversion. At the end of the bisque firing the clay has been sintered but not fully vitrified. The most common mistake in bisque firing is heating the ware too quickly. When this happens the water in the clay converts to steam, expands and explodes the clay around it. It is very important to fire slowly at the beginning of this part of the cycle. If the work is thicker the risk for these results goes up exponentially.
Market
The bisqueware market has dropped off in recent years. Many people have realized that it is more convenient to create or pour their own molds and save the time of having to go to a ceramic studio to do so.
Kilns
You can bisque in any of L&L's kilns. Our best advice is to take into consideration the size and shape of your work. For example, if you are making square tiles, then one of Da Vinci square or rectangular kilns may promote a more efficient use of space.
