Tips and tricks to using stilts.
Here are some tips everyone should know about firing ceramics on stilts.
Firing Temps & Cones
Most items fired on stilts are fired in a glaze firing to what the industry calls "Low-Fire" or "Earthenware" temperatures. Those temps are represented in an industry standard called CONES. A Pyrometric cone number represents something called "Heatwork". Heatwork is a combination of time and temperature to reach the proper firing maturity of a clay or a glaze. Low firing earthenware temps are commonly seen in the Cone numbers 06, 05 & 04. Or what we commonly call "Oh-Six" "Oh-Five" and "Oh-Four".
These low fire cone numbers represent a true firing range of approximately 1800 degrees F to 1940 degrees F. Most commercial bisque has been fired to cone 04 or approximately 1940 F. This bisque is ready for glazing as it is still porous. Once a glaze is applied and fired to the proper glaze cone, the ware will be sealed from water and other liquids.
Higher firing temps of 2200 F - 2350 F are called "High Fire" or "Stoneware" and are commonly fired to a Cone number of 5 or 6. (notice there is no 0 in front of the 5 or 6). The highest common pottery stoneware cones are Cone 10 or 11. Using stilts at these temps is risky. Metal points can bend, so use multiple pointed stilts, and do not fire heavy objects on stilts.
Mayco makes a higher fire stoneware bisque. They do NOT recommend ever stilting their stoneware bisque. Firing at stoneware temps make the stoneware soft in the kiln. In the firing process at high temp, many stoneware clays can deform or slump over the stilt. Dry foot all Mayco Stoneware, and test other higher firing clays as well.
We only recommend using a multi-point stilt when you fire to cone 5 to cone 10. The higher temp firings can warp metal points, and extra points are needed for strength! Only use stilts when firing at higher fire as a last resort.
Stilting your work vs. Dry Footing
In many cases, stilting can be difficult because of the shape of something glazed. Irregular non flat bottoms are common in some specialty shapes so using a "Multi-Point" stilt or a Bar stilt is recommended. Your average plate, dish, mug or bowl should be stilted with a 3-point stilt with the points just inside the foot ring or "lip" of the bottom. Make sure to not use an undersized stilt. If a plate is 5 inches across, use a minimum 3 to 4 inch stilt, not a 2 inch stilt. If too small a stilt is used the piece can tilt or slide into other pieces!
Some items are either stoneware clay or too unruly to put on a stilt. Wipe all traces of glaze off the area the piece will be resting on. Any part of the piece that makes contact with a kiln shelf must be completely free of glaze. This is called "Dry Footing" and is used when stilting is not an option. No glazed area of a piece can ever touch your kiln shelf! Also, never place dry footed stoneware bisque across two 1/2 kiln shelves as it can cause the piece to distort.
For High temp firing we do not recommend stilting unless you really must do so.