MYSTERY OF THE FIRE
June 17, 2015
The most difficult part of making a pot is the final step… firing the kiln. The glaze firing will test my pots. If there are any hidden weaknesses they will be revealed. There is always some parts of the pottery craftsmanship process that are out of my control, but the firing is the most so. Pots can be ruined by so many things. Being in the path of the flame (causes blistering on the glaze), a hidden “S” crack appears, not enough reduction, too much reduction, iron blowing around in the kiln from an unknown source causing blemishes, warping, too much heat, not enough heat, glaze just doesn’t look right, glaze runs ruining a design (some people find these pieces are the most beautiful, but that is a topic for another blog). I’m not sure about everything that goes on in there. I mean, I know, generally, but I am still mystified by something every firing. Opening the kiln is like getting to open Christmas presents, every time. It’s that exciting. Though after I open the “present” I’m not always pleased. It can be as great as getting a pony or it’s not what I wanted at all. When it’s the later, I feel like quitting my job and slitting my wrists. Don’t worry, I recover from this pretty quickly. There has been so much work and time invested in the pots by the time they get to the kiln. The kiln holds about a months worth of work: here’s a picture of pots ready to be loaded:
That is 9 boards filled with objects that are precious to me. It doesn’t look impressive but it is a huge investment of energy and resources at this point. Each pot started as a lump of clay that I had to wedge. Then it was thrown, trimmed, handles added as required, bisque fired (which requires loading, an 8 hour firing and unloading), waxed, glazed and decorated. Now I must load it into the kiln and blast it with 360,000 BTUs of heat for 10-11 hours until it reaches the point where it turns into a softened glowing 2360ºF mass. In ya go guys. Good luck on your journey. Hope I see you again.
I fire in a reducing atmosphere which means I starve the atmosphere of oxygen. This makes carbon monoxide, which wants to become carbon dioxide. To do so, it grabs an oxygen molecule where available, from the glaze or the clay. This causes glazes with copper to go from pale green to rich red and boring brown iron is reborn in lovely shades of pale green and blue (celadon). It makes my porcelain whiter than white with just a tinge of blue. Sometimes reduction is good. Sometimes not so good.
I judge the amount of reduction by the color of my flames, sound of my burners, amount of back pressure and temperature rise. Quick increase of temperature indicates oxygen which is what the fuel needs to create energy. Very slow rise of temperature indicates reduction as there is not a lot of oxygen to burn fuel. A very un-scientific approach to a very scientific process. Most of the time, it works. I take detailed notes EVERY firing. If I get a great firing I try to reproduce it exactly, down to how the kiln is stacked. Here’s a picture of the kiln well into the reduction phase. The temperature is about 2000º F. You can see the flames exiting from the spy holes.
After the 10-11 hours of firing I still have to wait another 15 hours or more before I can open up and see the results! I usually finish firing in the evening and a night of sleep greatly reduces the amount of time I am impatiently waiting to crack the kiln. In the morning I take the plugs out of the spy holes and peek in with a flashlight just to get a small glimpse. Sometime after lunch I finally get to open my “present”.
There they are… transformed by the flames. A lot of the pots will look how I thought they would. Almost 20 years of repeating the process has taught me what to expect. A few will surprise me. If I am lucky, it will be a happy surprise. The pot will surpass my expectations and will have extra bling. And I will be grateful (for I had not much to do with it). Most will be cleaned up, priced and packed for my next show (http://www.collegehillartsfestival.com/festival_info/). Some, sadly, will not meet my standards and will not make the cut.
What goes on in the kiln during the firing will always be remain somewhat of a mystery. Maybe one day I will fully embrace both the happy and not so happy accidents. Beauty is in the eye of the beholder, so I’ve been told. Now I must go price and pack pots. Heading to Cedar Falls on Friday morning for the College Hills Art Festival.