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Over 1500 quality clay and ceramic products for hobbyists, teachers, and potters.

General Information

How Much Grog?
As a general rule, larger work and tile usually demand more openess and tooth, which is accomplished by adding "temper" to the clay. Temper is added in the form of grog (crushed fire brick), kyanite, mullite or sand. Our clay descriptions give you an idea of what to expect. Keep in mind that many people break this rule with successful results.

Clay Consistency
One of the most challenging task is to mix clay to the proper consistency.If you need one of house bodies at a special consistency please inquire. Special consistencies can take up to 4-6 weeks depending on the mfg.

Bisque and Glaze Firing
When a ceramic product is twice fired, the first firing is called the bisque, or biscuit. The second is called the glaze firing. Stoneware and percelain (to be glaze-fired to cone 6-10) should be bisque fired to cone 04, although some fire to 08-07 with good results. Low-fire bisque should be at least a cone hotter than the glaze firing. Bisque firing drives off all the water in the clay structure and burns off much of the organic material. If the organics are not removed from the body, the outgassing will continue during the glaze firing. As trapped gases try to push through the glaze, they cause surface defects such as pinholes, bubbles, and craters. In low-fire ceramics, the glaze firing causes the glaze to melt and flow. There is no further change to the clay body. With stoneware and porcelain, the glaze firing causes the clay body itself to begin to fuse and become glass-like. This process, called vitrification, is accompanied by some shrinkage and a large increase in strength and hardness. At the same time the clay body is vitrifying, the glaze melts and bonds to the clay.
To control the bisque firing for best results, we recommend the following: (These suggestions apply primarily to electric kilns)
1) Loading: Do not stack or load bisque too densely in the kiln. Allow space for air to circulate among the pieces. Invert, rather than stack, similar pieces (bowls, etc.). Use stackers for tiles and plates.
2) Firing: For kilns without downdraft vents:Remove the top spy-hole from your kiln for all firings. This helps the kiln keep enough oxygen in contact with the ware. For kilns with downdraft vents: Keep the lid closed and peeps in. Keep the vent on during the entire firing.

Bisque Firing Schedule
The following schedule should take approximately 12 hours to fire. Adjust it according to your needs. If you're having trouble with blow outs, put a longer hold on steps one and two to allow for the escape of water. For pinholes and craters, increase the hold on step three, and bisque to 1940 F.
Bisque Cycle (using computer)
Segment 1: Rate-150 F/hour, Temp.-250 F, Hold- 1/2 hour
Segment 2: Rate-200 F/hour, Temp.-550 F, Hold- 1/2 hour
Segment 3: Rate-250 F/hour, Temp.-900 F
Segment 4: Rate-100 F/hour, Temp.-1350 F
Segment 5: Rate-300 F/hour, Temp.-250 F lower than desired bisque temp.
Segment 6: Rate-120 F/hour, Temp.-To desired bisque Temp.

If you are firing a kiln with a kiln sitter and switches, it's important to take note of the atmosphere in the kiln. The color of the atmosphere tells you what is happening in the kiln. For example, in the early dark stages, before red heat, gases begin to emit from the clay body, free and chemical water is driven off.
Bisque Cycle (using kiln sitter with no vent)
Segment 1: Bottom Switch-Low, Middle Switch-Low, Top Switch-Low
Hold- 3 hrs, Kiln Atmosphere- Dark, Lid- Ajar
Segment 2: Bottom Switch-Medium, Middle Switch-Low, Top Switch-Low
Hold- 1 hr, Kiln Atmosphere- Dark, Lid- Ajar
Segment 3: Bottom Switch-Medium, Middle Switch-Medium, Top Switch-Medium
Hold- 1 hr, Kiln Atmosphere- Dull Red, Lid- Closed
Segment 4: Bottom Switch-High, Middle Switch-High, Top Switch-Medium
Hold- 2-3 hrs, Kiln Atmosphere- Bright Red, Lid- Closed

Kiln sitter should cut off in 2-3 hours. Kiln can be pushed to temperature by turning top switch to high. However, before firing, check sitter to make sure it is adjusted properly. For safety's sake, use coneson the shelves in the kiln for visual check. If you have further questions, feel free to call or email us.