Thursday, November 10, 2011

Fourth Firing - Heat and Humidity - Sept 2011

We had been spending a lot of time on our farm, making trails for the woodlot tour in October to see our butternut grove. Butternuts  in North Anerica are all dying from a canker and so have been put on the endangered speices list. The search is on for a canker resistant tree - so far over 8000 trees over a wide geographic area have been examined by researchers and maybe only 4 are showing sign of recovery. These may then become the parents of future resistant trees if the trait proves to be genetic and can be passed on to future generations.

As a result of all the trail clearing I got a lot of white pine branches cut into firewood for my wood kiln. In addition I bought a truckload of cedar slabs in June hoping that they would dry a lot faster than any cedar cut this year.
Wood storage - cedar slabs on the left
Malcolm Davis Shinos ready to go into the wood fire - the large plate dunted in the firing - seems like it was on the way up as the glaze had run down the broken edges a bit. I think that I preheated too hot the night before and then let it cool before starting again the next morning.
I managed to get this firing in before the end of summer which has been very hot and humid. With all the humidity the shino glazes did not want to do their thing - that is getting that crusty white soda ash look from the soda ash migrating to the surface. To speed up the drying process I had heat-gunned the interior of my tall slab vases and then blocked the tops with plastic bags, thinking this would force the soda to the outside surface. This did not seem to work as little soda ash ended up on the outside surface, much less than normally. Thinking back, heating the interior would really have wicked the soda ash to the inside surface, even if the tops were blocked and the interior could not dry quickly. It would have been better to sweep the heat gun on the outside surface. The test that I had done at MISSA two years ago when I had placed the shinos in different situations - what worked the best was to place the pot in a sunny and windy location and you got great crusting patterns.

Below shows a test to see how ashes affect the cones - both are cone 10 - one was capped by the pot and the other was outside it. It seems like they were equal which is good to know, but maybe the outside cone was not subjected to too much ash where it was placed. I will have to repeat the test in the very front where there is a lot of ash.

I got some great chuns - on the left Jun 4 over Temmoku turned out a vivid blue/purple and in the front section some super carbon trapping - totally black except where for wax resist brush marks. This was MD shino without the Red Art and it results in more white instead of orange over porcelain. Unfortunately the tall vases ended up mostly an ugly shade of orange brown. I will have to try and refire them in the gas kiln. I am having trouble understanding why one pot gets it while another one next to it hardly any at all.
This time some of the carbon trapping also ended up as even speckling - rather like granular managnese, even where there was applique or lacquer resist/carving that was waxed out. I guess that is what makes shinos so exciting!