Monday, November 28, 2011
Nerikomi and Firing Temps
For the nerikomi platter pictured above I brushed different glazes on the flowers, stems, and leaves. The background has another glaze brushed on. The background glaze reacted with the minerals in the red clay and essentially is a neutral color but still appealing against the color of the flowers. This piece has me thinking about geometric shapes for a tile wall hanging and I'd like to try inlaid clay on a vertical surface. Every piece I make elicits exponential numbers of ideas.
This platter is a continuation of my ongoing experiments with nerikomi or inlaid clay. Years ago I made several plates with inlaid clay which were fired to Cone 10. Now that I'm working at Cone 6, I decided to do some tests several months ago where I inlaid circles of white stoneware into red stoneware clay. My miniature test bowls cracked after the glaze firing and the inlaid clay was beginning to jut out of the red clay. I also made a window with a red clay frame and white clay curtains and the red clay shrank and cracked the white curtains. The shrinkage rates for both clays were the same at 11 percent so I wondered why that happened.
After looking at the cones of the previous firing, cone 5 on left and cone 6 on right, I decided the kiln fired at too high a temperature the last time. Cone 6 is melted over.
I decided to reduce the hold time and raise the bottom cool down temperature by 100 degrees. From the left Cone 4, then 5, and 6. The platter fired without the previous problems of cracking and pushing the embedded white clay up. If you recall the glaze on the tin cup from this firing was shiny. With a longer hold time the glaze would be more matt. In the future I will have to fire the work according to how I want the glazes to turn out, some with less hold time and some with more.
For the bisque I used the cone fire program of 04 already in the kiln and cone 05 and 04 are melted over. I think my kiln fires hotter than the program says. I'll check the manual to see if I can adjust the programs to match the cones. How long do pyrometers last? Or how many firings should they last?
For this 10 inch bowl I impressed leaves into the wet clay. After bisque firing I hand brushed different glazes on the leaves and on the background and I used a different glaze on the rim and underside. I used the same color background glaze on this bowl as the platter above and it's essentially the same color as the clay but with a nice sheen. It has an earthy look which I find appealing. There are a couple of spots where the background glaze turned a darker burgundy color.
This textured platter came out nice because the red color of the clay shows through the texture giving it an antique look. More results from this firing tomorrow, so stay tuned. Thanks for all of your comments and suggestions, I really appreciate your input.