It’s Monday, and if you are one who notices patterns, you may have noticed that every other Monday lately, we have been rolling out a new free download for our subscribers. And guess what! Today is one of those every other Mondays!

 

Our newest download, Electric Kiln Firing Techniques and Tips: Inspiration, Instruction and Glaze Recipes for Electric Ceramic Kilns, is yours for the taking Ceramic Arts Daily subscribers! In today’s post, I am presenting an excerpt from it, which explains how Satori Yamaoka combines both oxidation and slight reduction to create amazing oil-spot surfaces in his innovative electric and propane kiln. And you can get the full article, plus the others by downloading Electric Kiln Firing Techniques and Tips from our free gifts page. – Jennifer Harnetty, editor.

 

 

 


Electric and Propane Combination Firing

 

One of the more interesting aspects of Satori Yamaoka’s firing method involves combining electric and propane, a method he has used for about 40 years. He has three electric kilns that go to Cone 9, all of which are designed to allow a small amount of propane to be used at a certain point during the firing cycle.

 

Using a computer that he has programmed to increase the rate of heat evenly with straight oxidation, electricity is used as the only heat source in the beginning of the firing. At around Cone 08, he introduces a small amount of propane to slightly reduce the atmosphere. This continues to Cone 9, which usually takes 24 hours.

 

This type of firing has evolved from considerations of cost and the colors Yamaoka wants in the finished ware. The kilns are large, custom-made, rectangular, top-loading electric kilns. The interior dimensions are 159 X 57 X 80 centimeters, (63 X 22 X 32 inches), with about 23 centimeters (9 inches) of brick and fiber insulation. Electric elements are anchored to the fiber hot-face. There are eight exit ports about 3 centimeters (1 1/4 inches) in diameter on the sides, front and back (two on each side). A ratchet-and-cable system lifts and holds the lid open.

 

Yamaoka fires about 10 electric/propane firings per month. The exact firing schedule varies a lot, but the first part is always electric guided by computer. There are always variables that affect the latter part of the schedule: stacking, which glazes are included, whether saggars are used, etc. So when the propane is introduced, things may change from firing to firing.


This article is excerpted from Electric Kiln Firing Techniques and Tips: Inspiration, Instruction and Glaze Recipes for Electric Ceramic Kilns, which is free to Ceramic Arts Daily subscribers.


Kiln Diagrams

Top cutaway view of rectangular electric/propane kiln. The manifold that delivers propane to the kiln extends across the length of the center of the kiln floor, with ports every 20 centimeters (8 inches).

Front cutaway view of rectangular electric/propane kiln. Four lid vents draw the propane through the kiln, ensuring even reduction throughout the stack of ware.
Glaze Recipes
Kujaku (Peacock) Glaze, Type 1 Cone 9, reduction
Glaze Material
Barium Carbonate 11%
Bone Ash 2%
Magnesium Carbonate 3%
Strontium Carbonate 6%
Whiting 8%
Potash Feldspar 42%
Kaolin 8%
Silica (Flint) 20%
Total 100%
Add:
Copper Oxide 4%
Tin Oxide 3%
Silicon Carbide 4%
Shinsha Glaze, Layer 1 Cone 9, reduction
Glaze Material
Barium Carbonate 18%
Whiting 7%
Potash Feldspar 38%
Kaolin 12%
Silica (Flint) 25%
Total 100%
Add:
Red Iron Oxide 1%
Satori combines several glazes (all of which are included in Electric Kiln Firing Techniques and Tips: Inspiration, Instruction and Glaze Recipes for Electric Ceramic Kilns)  to get the Peacock affect shown above. Because this glazing process involves several layers, thickness will affect the result.
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