1. Fully Dry Your Green Pottery
When pottery is first made, it is loaded with water. All atmospheric water must be evaporated as much as possible before the pottery is ready to be put into the kiln. Otherwise, problems with the clay body are quite likely to occur. Be sure to dry your pots slowly and evenly until they are completely bone dry.
Remember: Glazes and clay bodies need to be matched for temperature maturation as closely as possible. In nearly all circumstances, low-fire clay bodies should be used with low-fire glazes. Mid-range or high-fire clay bodies will remain too porous or "punky".
Since we are talking about bisque firing low-fire clay bodies, we can fire the clay slightly higher than the glaze. Usually, this means you will bisque fire to cone 04 (make sure you get the zero in there!), which will tighten the clay body just a bit more than a lower temperature will.
Once the pottery has been bisqued, cooled, and removed from the kiln, you can decorate it. Glazing your pottery can be an adventure of discovery, especially when you are using new glazes or using familiar glazes over a new, different colored clay body. Remember to use wax resist and coat the pot's bottom and up it's outer sides a quarter of an inch before using underglazes and glazes.
Raw glazes are not at all the same color they will be once fired, which can stretch your imagination as you work to envision what the finished piece might look like. If you have examples of the fired glazes, you may find it helpful to keep them near where you can use them as a reference as you glaze your new pots.
4. Glaze Fire Your Pottery
Stack your glazed pieces in the kiln after they are completely dry (usually just a few hours). Stack carefully; give pots a quarter inch clearance space on all sides and at the top.
The firing schedule for glazing is faster than for bisqueing. This is because the bisque firing has already transformed the clay into a ceramic material. Low-fire glaze firings are usually between cone 06 and 04, with cone 05 being very common. A typical firing schedule is:
- two hours with ramp at 150°F/hr
- three hours with ramp at 400°F/hr
- ramp at 120°F until the desired temperature is reached.