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Firing Art Clay Copper
by Pam East
Below, Pam describes her own personal method of firing Art Clay Copper...
Prepare your kiln by placing four small kiln posts (1" to 2") in the kiln and pre-heating it to 1780F (971C). Put a piece of fiber paper on the fiber kiln shelf, but do not put shelf in at this time.
Once the kiln has reached 1780F (971C), place the dry Art Clay Copper pieces face down on the fiber paper. Use a pair of very long tweezers or pliers, and a heat glove, to place the entire shelf in the kiln on the kiln posts.
Fire the pieces for 30 minutes.
When the firing is complete, use the long tweezers or pliers and the heat glove to remove the shelf from the kiln and very quickly dump the contents off the shelf and into a bucket of cold water. The faster you get the pieces from the kiln to the water, the less fire scale will form.
After quenching, place the pieces in heated pickle such as Sparex for 15 minutes to an hour depending on how much scale formed. When the black scale has turned to a brownish color, it will brush off easily. Only use copper tongs in your pickle, and rinse your pieces in clean water.
Use a wire brush with soap and water to brush your pieces, and then tumble them to bring them to a lovely shine.
Patinas may be added using either Liver of Sulfur or a torch. You can also inhibit the rate of oxidation by applying a thin coat of Renaissance Wax.
I fire my pieces face down, because less fire scale forms on the front of the piece that way. I use the fiber paper to prevent the piece from sticking to the kiln shelf. I like to place the pieces on the fiber paper on the kiln shelf outside of the kiln to reduce the amount of time the kiln is open. By having them set up on the shelf and then transferring it into the kiln, you can put all your pieces in at one time very quickly. The kiln posts make it easier to take the shelf in and out. Likewise, I remove all the pieces at one time by taking the whole shelf out and dumping the pieces off into the quenching bucket rather than pulling the pieces out one by one. By doing it this way, you greatly increase the speed with which you get all the pieces quenched. If you take them out one by one, the first piece may not have much fire scale, but by the time you remove the last piece it will have cooled too much and there will be a lot.
Pam is a Master Instructor for Art Clay and author of Enameling on Metal Clay.
Last updated on Thu, July 15, 2010 by Metal Clay Guru