Advice on a Raku glaze
Posted 01 May 2013 - 02:25 PM
Soda Ash 30.5
Lithium Carbonate 8.5
Black Copper Oxide (added) 2.5
There have been a couple instances where this glaze yielded a lovely mix of vibrant blue-greens, with every shade of red and orange on the sides. Here's an example.
More often, though, I get either an algal green, or a brick red (or copper). For an example of the former, see below.
I'd like to get the first result more consistently. Yes- I know Raku is a chaotic process...
My theory is that the first result stemmed from several factors...
1) Less maturity at the tail end of the firing process (and thus a 'sandstone-like' texture)
2) Thick glaze application
3) Fast transfer of the piece to the reduction chamber
4) Intense but brief reduction, with the piece pulled early and rapidly cooled
These were the conditions for the firing for the piece at the head of the page. However, when I tried to duplicate these conditions recently, here's what I got...
Not bad... but not exactly what I'm going for.
Any suggestions appreciated!
Posted 01 May 2013 - 02:50 PM
Kiln Repair Tech
L&L Kilns Distributor
Owner, Neil Estrick Gallery, LLC
Posted 01 May 2013 - 03:34 PM
As you said, Raku results will vary based on firing temp, glaze thickness, degree of reduction, cooling speed, etc. You need to experiment with many pots, only changing one variable at a time to see what gives you the best results. It different for every kiln, every firing situation.
Mostly, I was curious as to whether anyone had used a glaze with similar chemistry/characteristics, and had suggestions on ways to narrow in. There are a lot of variables to tweak otherwise!
Posted 02 May 2013 - 06:06 AM
So, you just have to be consistent in how you apply the glaze and when you pull them out and how fast you get them into the reduction.
Marcia Selsor, Professor Emerita,
Montana State University-Billings
Marcia Selsor Studio in Brownsville, Texas.
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