Sunday, May 08, 2011

Cool Waiting

I was just out peeking in the spy holes. The pyrometer is reading 540 degrees still so it is going to be a while. The rule of thumb I was given was that if you could stick a roll of paper into the spy hole and it didn’t burn or smoke, you could open the kiln. [Fahrenheit 451 for Ray Bradbury fans] I have done this, but found the “Ting Ting Ting” sound of the glazes crazing just too nerve racking. So, I go a little slower…

The process of the firing seemed to go well. I did it a little different this time. I have been starting the pilot burners at 10 or 11:00 pm the night before and letting them burn until I get up the next day and light the main burners. The kiln would reach about 450 degrees. This time I just left it until the morning of the day of the firing. I lit the pilots let them burn an hour and then cracked on the mains and let them burn an hour. From there I boosted the pressure 1 psi and hour until I reached 4 psi. I set then damper at 5 inches open and it is in cruise control. When Cone 010 goes down, I pull the brick out of the passive damper and let the kiln go for an hour in body reduction. Usually Cone 080 goes down during this. Back in cruise control the kiln climbs towards Cone 10 (~2350 degrees). I finished up maybe an hour later and saved a few bucks.

It is then time for the fun. I mix 3 gallons of hot water with 3 lbs. soda ash, 1 lbs. salt and ¼ lb. borax. I put this in a sprayer, open ports in the kiln and spray.

When Cone 10 goes down, I shut the burners off and let the kiln cool until 1900 degrees. At this point, I relight the burners and hold that temperature for an hour to foster crystal growth in the glazes. This adds depth to their color if I can get it to happen. The whole firing process is like that. You try your best to control it, but in the end, the kiln Gods give you what they want.

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