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mason stains & "dusting" defect

updated thu 9 apr 98


KarenY31 on wed 8 apr 98

I am firing Mason stains to cone 6 oxidation. The stains are painted on top of
a white base glaze. I'd prefer to use a frit (3124) because the stain mixed
with the base glaze is a thicker material. Mixed with Gerstley Borate the
stain is too faint colored. However, even with slow firing, the colors
(black, green, blue, red) mixed with varying amounts of frit, seem to be
flaking off and forming a dust in the bottom of the bowls. On flat pieces the
colors seem to explode upwards sprinkling the surrounding area with "fairy
dust". There are also a lot of white lines in the colored areas where the
glaze has disappeared. This happens with recently & not recently glazed
My glaze includes Gerstley Borate, Kona F4 Feldspar, EPK Kaolin, Whiting,
Flint, & Zircopax 12%. With the kilnmaster set on Slow cone fire 6, the
heating phase takes about 14hrs.
Has anyone else encountered this problem? Advice welcomed.
Thanks. Karen Yuan
PS Are transcripts of earlier messages available?