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Clay Art Web Guide
FAQ# 2 Pit Firing Techniques
I would love to hear about any tricks to the trade if you would be willing to share them. The problem that I always encountered with pit firing was the lack of heat and not getting my pieces to fire completely through. I always used sawdust for my fuel, but I suppose that my clay could have had too high of a cone for the pit fire.
One thing about using straight sawdust is that you don't get very much heat. You are actually choking your fire back. When you run a kiln, you need fire and oxygen. What I am doing is laying down a bed of six inch sawdust and then placing my work in and on top of that. The work is about maybe 1/5 in the sawdust. Then I build a bonfire around the work and keep stoking it for several hours to get the temp that I am wanting. I am firing with cone six
clay. You would not want to fire with a clay that takes becomes more vitreous at a lower temp because it will not take the fuming that you want it to. Rather, it will repel it. I am using saggars to fire in also. This keeps the fumes from escaping. Other pieces are fired in the open though and have chemicals placed around them. Root killer otherwise known as bluestone which can be purchased from Wal-Mart is a good source of copper
and actually fumes better than copper carbonate. Salt is important. But, do not use too much or you will get a build up on the work and it will attack the surface. Then there is ferric chloride a good source for which is computer etchant which you can obtain at Radio Shack. Well, that is about all I know. The rest is luck!