Wednesday, October 22, 2014

The Fire has the Last Word:

Mary Paliescheskey-2014

Working in clay requires a few steps and two firings in the kiln. The process isn’t complete until the piece comes out of the final firing. You never know what will happen in the fire of the kiln. The fire does what it wants -Magic or disaster.
The process begins with the building of the piece in clay. I use Long Beach White which can be high fired and is basic clay. Prior to the first firing, the piece needs to dry completely. At this point the clay is very fragile and can be easily broken. If you pick it up by the edge-that edge may just snap off. This is such a sad thing to happen to something that you spent time creating. It is considered greenware.
Drying clay looks
the same as bisque
This first point is where many things can go wrong. First, if the piece isn’t completely dry, you may open the kiln to find a broken piece. The water left in the piece will expand to water vapor from the high heat in the kiln. This rapid rise in temperature causes an expansion of liquid to gas-resulting in the water now taken up a much larger amount of space. The expansion breaks the piece. Another problem could be that you left an air bubble when you joined two pieces of clay. You’d think that wouldn’t matter. A gas is a gas, but as Boyle’s Law tells us; the volume of a gas is dependent upon its temperature. The higher the temperature the larger the volume that is needed. Again the piece can be broken. Open the kiln and see what you have…
 Once it is bisque fired (survived the first firing), you are ready to glaze the object. Choices and choices-there are many. What color glaze do you want? Are you using just one glaze or several? If you over lay glazes, you end up with three colors. The first color, the second color, and the third where the two mix. And guess what! The order that you put the glazes on matters. Color A then Color B gives Color C, BUT Color B then color A gives and entirely different color. There are really unlimited choices. I hope you can make a decision. Now here comes the surprise. Even when you think you know what will happen with the glazes. It’s only a guess. The fire in the kiln decides how things turn out.
You don’t believe me. Well, look at these two goblets. I glazed them in exactly the same glazes in exactly the same order, on the same day. Fired in the kiln and out they came a bit different. I have actually never seen the brown color with Carbon Trap Shino before this. Surprise!
The fire really has the last word.