Tips for working with Ceramics
Sometimes a firing cycle for a particular glaze (e.g. a ‘copper red’) will include various stages of oxidation and reduction. Re-oxidation brightens up a glaze, although the effect will usually still be different from a pure oxidation firing. Re-oxidation is often done towards the end of a firing cycle, in order to eliminate excessive carbon trapping, which could result in dullness.
Stilts cannot be used to support porcelain bisque as they become embedded in the porcelain when heated to high temperatures.
A ‘limit timer’ is the term used for the timing device that may be installed on a kiln to shut off the power at a predetermined and set time.
Pyrobars serve the exact same function as Junior cones in the Kiln Sitter, except Pyrobars aren’t tapered and provide a more reproducable firing.
If firing a new glaze you are unsure of, put the whole piece on a piece of bisque you have pre-made. Then if glaze runs, it will run onto this piece instead of ruining your kiln shelves.
Mid to High fire glazes often look better if they are cooled slowly. For this reason 3″ brick is preferable for high firing. However, it is possible to slow down the cooling by “firing down”. With a manual kiln, when you would normally turn the kiln off, instead turn the switches down to medium. With an electronic kiln, you will want to program this ahead of time. As an example, your last segments could allow rapid cooling to 1950 degrees F, a 30 minute hold at that temperature, then slow cooling at a rate of 150 degrees per hour down to 1100 degrees F. At that point the kiln would turn off.
Be sure that at least one element groove is between the top shelf and the top of the kiln.
The first layer in the kiln should be small, light pieces.
Raku Pottery is earth derived…the firing process is unique and daring, and in the eyes of the Zen Masters, the process truly reflects the most fundamental rhythm of enlightened life.
Items may be stacked on and inside one another for bisque firings. They won’t stick together. However, you can cause problems by doing this.
* The carbons may not burn out completely from an area that is covered by another piece, and this may cause defects during the glaze firing.
* Some items may break if they are not allowed to expand and contract freely. So if stacking two bowls for example, make sure there is plenty of room between them. Remember that items will shrink during firing.
* Stacking may cause more uneven temperatures throughout the kiln.
* Some people think the tighter they stuff the bisque load, the better. And you may have success with this method. But other people find that they do better when pieces are given space.
My advice is that you can pack a bisque load tighter than a glaze load, but don’t overdo it.
You can fire overglazes directly on porcelain bisque but you may have to use a hotter cone. These overglazes can be applied directly and fired in the 017-015 range.