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sv: re: cone 10 glazes to cone 5-6

updated fri 15 jun 01


Alisa og Claus Clausen on wed 13 jun 01

Hi Tom,
Glad to hear you are so actively testing glazes for your planters.
I wanted to mention that I try really hard not to "editorialize" my =
glaze test results with adjectives like great, not great, like, no like. =
Of course at times I do say that I think is a glaze has a great feel or =
nice color. But even then I go lightly. I do this rather on purpose so =
people, like you, who read the recipes, must make their own tests of =
course, and from them make their own aesthetic judgements according to =
what they need the glaze to do for them. On the other hand, when Ron =
R,John H. or others says a glaze is foodsafe, I jump!

Good luck finding the glazes you need. Also, let me know if you looking =
for more than browns right now, I have some new pretty colorful stuff, =
but still on the quiet side.

Best regards,
Alisa in Denmark

I searched thru the archives for cone 6 glazes with the
> adjectives beautiful or great and have tried several glazes on test =

Paul Lewing on thu 14 jun 01

When I made that switch about 15 years ago, I too tried to get all my
cone 10 glazes down to midrange temperature. Some I did have some
success in getting usable recipes using what I refer to as the TIFTIM
method (Throw In Frit Till It Melts), but they were never the same as
the cone 10 version.
The problem is that in a cone 10 recipe you can have so much more
alumina and silica. So in many recipes, such as copper red recipes, you
can remove all the clay and all the silica, and you still have more
Al2O3 and SiO2 than will melt at cone 5 or 6. This is why substituting
Neph Sy for feldspar can lower the firing temperature a cone or two. NS
is essentially a low-SiO2 feldspar.
But usually you can't make an equivalent glaze out of the same set of
ingredients. The TIFTIM method usually involves a calcium/boron frit,
so you've radically altered the flux balance and probably introduced a
whole new element, the boron. As I said, it can result in interesting
glazes, but they won't be the same.
Also, most people make a switch in atmosphere, from reduction to
oxidation, when they make that temperature switch, and that will alter
the look of the glazes more than the temperature will.
Happy testing,
Paul Lewing, Seattle