[Clayart] Blue haze on kiln shelves (The Back Story)

[Paul Lewing]

On Nov 11, 2022, at 6:27 AM, Dragonbelly Ceramics <lisa at dragonbellyceramics.com> wrote:
t the revision takes the glaze from being out of 2 of the 3
limit formulas to right at the sweet spot where they all overlap.
The thing to know about limit formulas is that they are not hard and fast parameters.  If you’re designing hotel china or commercial dinnerware, you want everything to be within the limit formulas.  But all the really cool glazes have at least one element that is outside the limits.  I designed a zinc base and a magnesium base by starting with a value for each of those elements that was double what limit formulas said was allowed, then filling in the rest to get the surface and fit I wanted.  If one element is way outside the limits, that just means that that glaze will be strongly characterized by the element.  Up to a point, of course.  You get Al or Si too far out and your glaze won’t melt at all.

My next question is this: Is there any way to tell, other than mixing a
test, how the color and glaze behavior will change as the chemistry changes?
Seger formulas will not, in themselves, tell you anything about color.  They will tell you about surface gloss or mattress, and fit.

Paul Lewing
www.paullewingtile.com  <http://www.paullewingtile.com/>
www.paullewingart.com <http://www.paullewingart.com/>
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