This is my blue ash glaze, it turns yellow where the ash hits it. I love it.
So, I fired in about 6 hours. When I was in college my prof. taught me to fire the cone 10 reduction kiln in about 7-8 hours. He had it down so he could start it up when he got to work and shut it off when it was time to leave. His advice was to get the reduction right, soak it when you need to, let the glazes melt and then seal it up tight and let it cool for 2 days. Some of the best fired pots I've made have come out of that kiln. The idea is that as long as you fire through the atmosphere that you want and let the glazes melt it'll be fine, the color/surface comes in the cooling. My flashing comes from the flame carrying the salt, if you woodfire and want flashing from just the flame this clearly won't work. Think about raku, fire it up to 1800 in an hour, as long as the glaze melts you're ok. I've wanted to "fast fire" for some time but have never wanted to risk it. This time I was foreced into a position where it was either fast fire or not at all. The firing was a bit of a hail mary but it paid off. There are "rules" to this though. If you single fire clearly this isn't an option. I use a very coarse clay body, lots of fireclay and grog, so it can take thermal shock. I don't think porcelain or fine grained clay bodies would do so well. So here is the firing schedule I used(everything except cone packs were bisqued):
1.5 hours: ambient to 900 degrees.
1.5 hours: 900-1200(begininning of red heat.) My friend Kent says that ash glazes need to go slow here to avoid blistering, my experience says he's right.
1.5-2 hours: 1200-cone 5.
1-1.5 hours: cone 5-cone 9 sometimes my kiln will just fly through this temp range and it's difficult to hold it back. I get good glaze melt in an hour here. I also fire neutral, which is theoretically the most efficient way to fire, reduction will slow this down.
Here is an interesting article by Marc Ward.
So long dudes.
7 comments:
Way to push it Brandon. You know I really appreciate the fact that you know what you're doing. I mean, lots of people out there do stuff and then make things up to justify what happened. You clearly knew that this would probably work. Probably. Of course we both know things can go wrong, and you know your parameters. Nicely done.
probably indeed. there was huge chance for error but it was nice to know that my research and experience was on my side. all those hours of reading ceramics publications in college have finally paid off.
Hey brandon, crazy how it goes yellow like that...i like it a lot.
btw where did you find the plan for that box joint jig you used on the treadle wheel?
Hey Brandon: This is great info, I'm about ready to gas fire my kiln and have been researching a firing schedule. I'm all about the faster firing since I'm doing Raku. I think I'll give this a shot, all the stuff I have to fire are all test glazes and test shapes, so there will be no great loss. I love experimenting, great way to learn something!
Great info on the firing, thanks so much; beautiful tea pot.
What a lovely tea pot, you must be really happy with it. Thanks too for solving the pb&j riddle, I must try it one day. Great information too about your firing schedule. Very helpful, thanks.
nice surface... looking forward to more pics
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