joan woodward on sun 29 dec 02
I read with interest John H's recent response to Kristin. It sounds like John is saying we can shorten the cooling cycle somewhat. I have a computer controlled Skutt. My current firing goes as follows:
200d/hr - 250 F
400 d/hr - 1000F
180d/hr - 1150F
300d/hr - 1894F
108d/hr - 2180F with 10 min. soak
350d/hr - 2080F with 20 min. soak
350 d/hr - 1950F
150d/hr - 1100F
I use the 350 degrees instead of 9999 because I remember reading some horror stories on Clayart of malfunctions using the 9999 setting. My guess from reading others' schedules is that mine could be simplified. My results with John and Ron's glazes are generally good, though I'm getting more semi-glosses than mattes. Not sure how to translate John's remark about starting the soak when cone 6 is at 2:00 o'clock to my computerized kiln. Would appreciate other suggests as well.
Separate questions: I like to do fairly precise design work on greenware with Easy Strokes on some of my pieces. I'm finding whatever clears I use (will be testing John & Ron's next glaze firing), my Ash clay from Mile Hi tends to bubble, especially but not exculsively on rims. I've fired it higher and lower, with no change. Had the same problem on Cone 5 BMix once. Used PZN from Clay Art Center, AMACO zinc-free, Duncan. Tried some recipes but they didn't seem to work well over the Easy Strokes. So. . . 2 questions: first, any thoughts on why I'm having this problem? And, second, I'd love to find a majolica glaze over which I could apply Easy Strokes on bisque ware and keep their precision. I'm not looking for washes. Would particularly like it to go over a dark stoneware, Mile Hi's Chestnut.
Any thoughts on these queries would be greatly appreciated. We're bringing Ian Currie to Grand Junction in April, but I'd love some help before then!
Thanks in advance to you generous folks!
Joan, on a day so sunny and warm I'm tempted to forego all my "desk" chores and take the Sunday paper outside!
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John Hesselberth on sun 29 dec 02
> I read with interest John H's recent response to Kristin. It sounds
> like John is saying we can shorten the cooling cycle somewhat. I have
> a computer controlled Skutt. My current firing goes as follows:
I certainly think you can shorten the cycle from peak temperature down
to 1900 and maybe 1800. Get through that as fast as you can. If you
don't want to use 9999 then use 750 or 1000-- that's about as fast as
the kiln temperature can fall anyhow. Then if you are still not getting
good mattes, slow down even more from 1900 down to 1500. I have a set of
samples that show Variegated Slate Blue cooled fast is glossy as can be,
cooled like the book recommends looks about like the book, and cooled
very slowly (50 deg F through that range) is a very dull matte. This is
what I would recommend to Diane--take varigated slate blue and cool is
really slowly one time--then see if it mattes for you.
I am coming to believe that you can spend too much time at/near peak
temperature and the cones may not show it, but you will have difficulty
getting these glazes to matte on the way down. I have some experiments
to do before I take a strong position on that. I think that is much of
what happened to Kristen and I think I have seen it myself, but my
experiments have not yet been well enough designed to prove it. There's
always more work to do to understand this complex craft of ours.
On Sunday, December 29, 2002, at 02:26 PM, joan woodward wrote: