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cone 8 glaze down to ^6

updated sun 16 oct 05


elark1@VERIZON.NET on fri 14 oct 05

for many years i have been using the following glaze on my porcelain. but i have now gone down to ^6 - thanks to ron r. and john h. i love my new glazes, but i have some customers from old who need replacements of their plates, bowls, etc. i would like to use the ^6 porcelain and perhaps the same glaze adjusted to the lower cone temp. i am having difficulty getting it down to ^6 and could use some help.
the original glace was called eggshell or bone and its formula is
cornwall stone 50 gms
ky ball clay 15
dolomite 20
bone ash 10
after i did some adjustments i made it up for a cool ^8
cornwall stone 53
ky ball clay 13
dolomite 21
bone ash 10
flint 3
but now i need help to bring down to a true ^6. can anybody help me??
eleanor arkowitz
in soggy wet, grey,and cool in n.h.,usa

Daniel Semler on sat 15 oct 05

Hi Eleanor,

These two recipes are almost identical. I would not expect them to be very
different. I note that the first only sums to 95 grams. Is this correct ? You
mention having difficulty reducing the maturation temp. What have tried so far

Anyhow, my first inclination was to try using a boron containing frit, but I
then became interested in the possibility of using strontium carbonate and/or
zinc oxide. Its not far from where you are to where you want to be, and just
diversifying the fluxes a bit might be enough. It would be interesting to try.
Having said that it looks like this glaze is an opaque semi-matte
off-white. Is
this close ? It seems it may rely on the dolomite for a silky or buttery
surface. Is this true ? If so then the boron might be a better way to
go as the
other method tends to reduce the MgO.

So let me know a little more about the glaze and I'll take a crack, unless my
vague ramblings above are sufficient for you, in which case great. The boron
approach is the same as what I did with Luba's clay mattes. If you want to try
monkeying with the SrO and ZnO approach it may take some more testing but the
info gained would be way interesting.