The Secret World of Firing

When you are a student of ceramics or working at a public studio, there is a part of the process that you never get involved with—the firings. You make your pieces, glaze them carefully and full of anticipation you put them on a designated shelf. At some point, they just come back to you finished!

The whole transformative process of firing is hidden. This is not a deliberate ploy–it’s just expedient and safe.  Handling other people’s work is a responsibility and understanding a particular kiln with the many possible firing plans takes a lot of experience with that kiln. And that takes time and repetition.

You probably already know that there are two different firings that have to happen before a piece is finished—a bisque firing and a glaze firing.
The bisque firing takes your work from dried mud to a hard yet porous state. It won’t disintegrate in water but it’s still a bit fragile and not fired to full maturity. It’s ready for glazing when it’s in this state.
The glaze firing takes your piece to maturity. The particles of clay are fused together and the glaze has melted. If a piece is high fired the glaze is not only melted onto your piece but fused into the particles of the clay.

Work has to be completely dry-bone before it can get bisque fired. Bone dry work is very fragile so this is when the responsibility for handling other people’s work comes into it’s own! I’m very careful at this stage and pay attention to where my hands are, how they’re moving through space and what’s nearby at all times.
Pieces in a bisque firing can touch each other because they won’t stick together. So, work can be stacked as long as smaller goes on top of larger and not much goes on top of large flat pieces-plates, plaques or platters.

Glaze firing has a different set of requirements. The purpose of this firing is to leave your work with a finished surface and there are many ways and different kinds of firings to achieve this. Work going into this firing has to be free of glaze on the surface that will touch the shelf or it will stick when the glaze melts, damage the kiln shelf and ruin your piece!

I have to give a bit more technical info at this point to make this next part comprehensible so stay with me.
Every firing is measured with ceramic cones. These are bits of material manufactured to melt under certain conditions. It takes a progression of temperature and time to make this happen. The expertise of the ceramicist comes in understanding how to make this progress happen in a manner that’s compatible with the desired results–for that kiln. Phew!!

I have to give a bit more technical info at this point to make this next part comprehensible so stay with me.
Every firing is measured with ceramic cones. These are bits of material manufactured to melt under certain conditions. It takes a progression of temperature and time to make this happen. The expertise of the ceramicist comes in understanding how to make this progress happen in a manner that’s compatible with the desired results–for that kiln. Phew!!

The most common glaze firing is straight forward cone firings, ranging from low to high. Your clay and glaze should have matching cones to get the best results. But like everything in ceramics, there are two kinds of cone firings, oxidation and reduction. This has to do with whether the atmosphere in the kiln is full of oxygen or reduced in oxygen. These different situations cause very different results in glazes. There are also atmospheric firings that introduce a volatile mineral like baking soda into the firing at the appropriate time. And finally, there are specialized firings like wood, pit or raku. I’ve probably missed some, but you get the idea that variation just goes on and on.

Glaze firings at my studio are straight forward oxidation. They are either mid-fire or high fire depending on the glazes. Even within those very simple parameters there is vast amounts of room for variety. You never get bored with ceramics!
All this might make you more interested in the firing process or glad to let it happen without your involvement. Either way, you have a little bit more understanding of what happens when you leave your work on the shelf.

Next Class Session

The next class session will be starting near the end of March so look out notification!