Sunday, August 22, 2010
One that Got Away. Green pots, white pots, and testers.
This is a detail of "one that got away". It was a large pot of a different shape that I hoped would be a good one for crystalline glazing.
This is it soon after unloading from the kiln still on its glaze catching saucer and stand. Everything looked like it was OK until a few days later when I went to pick it up and found that the base had separated from the rest of the pot.. Ooooops! A nice clean break right around.
It had actually crossed my mind that this pot might be vulnerable to something like that happening. I had potted this one quite thickly as I had planned on a good pool of glaze inside, and realized that this could be a likely cause of stress. I guess that the walls of the pot air cooled much faster than the base did, and ..., in the end something needed to let go!
In retrospect I should have let this pot cool right down to room temperature in the kiln before unloading it, as this would have kept the temperatures around the pot more even as it cooled.
Anyway, "we live and learn", as they say, and it is much better that a technical failure like that happens here where I can observe it and add it to my knowledge.
Most things in that firing turned out well, I am glad to say. I had 8 or 9 small pots in the kiln with this larger one, and some more glaze tests.
I am still playing with liner glazes, simple glazes that I put inside the pots. I either use a dark one, like the iron rich one in the pot above, or I am tending to use dolomite matte glazes, which give a smooth off white that sometimes looks really good where the crystal glaze has dusted over it. On one pot that I fired recently, the only good part of the glaze was where the crystal glaze overlapped the dark iron glaze inside. It produced a flowing chun-like blue that I want to experiment further with.
The pot above had a new crystal glaze on it that really didn't do what I intended it to do, but I do like what it came up with! The pot has a dense pack of small crystals all over, and is stone-like to touch. To get the large, separate crystals that I intended from the glaze, I am going to either, take it to a higher top temperature, hold it at the top temperature for longer, or add some more flux.
This white glaze really does make me think of wedding dresses decorated with floral designs. It is a glaze I tested a couple of month's ago, and I have started to use on finished work.
Above is a glaze test that has lots of possibilities. I like the cold, almost violet undertone to this white. This is another glaze that has to go up in temperature to do what it really should, but the stony quality of this test really appeals to me, and would be good on something sculptural.
Above are two tests with 3 percent nickel added to different glaze bases. Again, both under fired, but the colours are fascinating.
You will have notice rather a lot of green pots this time around. I hope to build up a little collection of them for an experimental reduction firing or two. I will be trying to turn some of them red by firing them to about 800 degrees Centigrade in a wood fired kiln, then starving them of oxygen until they are below about 500 degrees Centigrade. Don't worry, I won't do it to all of them.... I like the green, but it will be a wonderful thing if I can get some reds happening too!
I have been making some smaller crystalline glazed pots over the last week, anything from about 5 - 7 inches in height. I have an electric kiln load of them to pack and bisque fire tomorrow.