About My Stones
Chinese Blue is no longer available, except in occasional one of a kind pieces
Each of the stones is handmade using stoneware clay. They are shaped and flattened and then must dry thoroughly. Once they are dry, they are fired in a bisque kiln, which goes to 1700° F. This bisque firing serves the purpose of giving the piece considerably more strength than it has when it is simply dried clay and the piece won’t break while I handle it. The bisque firing leaves the "stone" porous enough that it can readily pick up glaze from a suspension of glaze materials in water.
The next step is glazing the stones. Each piece is hand painted with the glazes developed by Pamela Owens of Jugtown Pottery. The glazes are mixtures of local clays and inorganic materials such as crushed rock, oxides and various types of ash, to create a glass-like coating. These are specialized glazes and produce colors that you can't find in commercially developed glazes. Glazes are very thick and the porous bisque ware will quickly dry the first coat. I use several glazes together, and must be careful that the stone is thoroughly glazed, but that the glaze doesn’t run off the stone, or it will stick to the kiln shelf.
At Jugtown they do weekly firings in the gas kilns, and specialized firings in wood kilns and the reduction gas kiln and I fire in my electric kiln in my studio. Many of the stones that I do are done in the oxidation firings, which are heated to over 2200° F. The term oxidation firing refers to a when the atmosphere in the kiln contains oxygen. Oxidation produces brighter shiny colored results due to the oxides used.
The colors I get in these kilns come from combining glazes such as the greens from Weathered Bronze, blue from Blue Ridge Blue and turquoise colors from Chinese Blue. Tobacco Spit produces the neutral browns and Mustard the earth tones.
The Reduction firings yields a warmer clay body and textured glaze results. Reduction firing is when you reduce the amount of oxygen in the kiln. Copper oxide can produce a beautiful red in a reduction firing, which comes out in the Chinese Blue or the beautiful color in the Peach Bloom. In fuel burning kilns, the carbon from the burning materials combines with the oxygen in the kiln. When more carbon exists in the atmosphere than oxygen, carbon and carbon monoxide form and begin to take oxygen from all available sources including the oxides in the clay body and glaze. Impurities and trace metals in the clay and glaze will react with carbon in the kiln atmosphere to create spotting. Reduction kilns are special events at Jugtown, and a lot more work is required to attain good results. Therefore, the stones acquired from these firings are highly prized and sought after.
To achieve the depth and multi-dimensional colors the stones are fired a second or even third time. Sometimes, if the reduction is too heavy, a second firing in oxidation will bring out a wider variety of tones and color. Therefore, the process to this point can take over a week to achieve. And of course, the reduction firings are not done regularly, so the wait for those stones can be considerable!
The final step before setting the stones is to clean them so that they will fit properly in a bezel. The stones are individually ground on a grinding stone, when necessary, to ready them for setting.