Steve Slatin on tue 8 nov 05
Lili --
I read somewhere (and I absolutely cannot remember
where) that zirconium dioxide can be substituted one
for one with zirconium silicate. If this is true, the
reason we use the silicate is probably that it's less
expensive to obtain/refine.
I'd also speculate -- and this is just crackpot theory
here -- that part of the reason is that often we put
opacifiers 'below the line' when we calculate glazes.
The glaze doesn't know how we think about it, and
reacts as though those things were above the line ...
and since must glazes are primarily a glass former and
a stiffener, our glazes react more consistently when
what we put below the line most closely resembles what
comes above. Zirconium silicate is closer to a glaze
in characteristics than ZrO2 by itself, so we probably
have better results tossing it in.
Then again, what do I know? Last month I ginned up a
new green glaze trying to get a synthetic celadon in
oxidation at ^6 and it's green enough and clear enough
and it crackled, but the crackle is all wrong ... not
small and regular, but large and irregular. Got much
better results last week on an uncracked clear (don't
tell Mel!) blue. Boring over white stoneware, but it
looks like it should be good over a really colorful
body.
Best wishes -- Steve Slatin
--- Lili Krakowski wrote:
> If I remember there was Opax, Ultrox, Zircopax,
> Superpax....and half a dozen
> more. A pax on all their houses....they come up
> like evening star and then
> are gone...
>
> Question: Why do we use these products instead of
> plain old zirconium
> oxide?
> Can one use plain old Zirc?
>
>
> Lili Krakowski
>
> Be of good courage
>
>
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Steve Slatin --
And I've seen it all, I've seen it all
Through the yellow windows of the evening train...
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Lili Krakowski on tue 8 nov 05
If I remember there was Opax, Ultrox, Zircopax, Superpax....and half a dozen
more. A pax on all their houses....they come up like evening star and then
are gone...
Question: Why do we use these products instead of plain old zirconium
oxide?
Can one use plain old Zirc?
Lili Krakowski
Be of good courage
Steve Irvine on tue 8 nov 05
Hi Lili,
Zirconium oxide can be used in a glaze, but to make it disperse more evenly throughout the glaze
(it can clump together and make little white dots on its own) it is ground to an optimum size and
then the particles are coated with various proprietary mixtures that go by different trade names.
Steve
http://www.steveirvine.com
>If I remember there was Opax, Ultrox, Zircopax, Superpax....and half a dozen
>more. A pax on all their houses....they come up like evening star and then
>are gone...
>
>Question: Why do we use these products instead of plain old zirconium
>oxide?
>Can one use plain old Zirc?
>
>
>Lili Krakowski
John Hesselberth on wed 9 nov 05
On Nov 8, 2005, at 8:08 PM, Lili Krakowski wrote:
> Question: Why do we use these products instead of plain old zirconium
> oxide?
> Can one use plain old Zirc?
Now Lili, what would be the fun if we didn't make it a little bit
confusing?? As I understand it Zirconia = zirconium oxide = zirconium
dioxide = Opax.
Zircon = zirconium silicate = Zircopax = Superpax = Ultrox. Did I
miss any?
Either will do the job, particularly if you account for the silica in
zirconium silicate; however, zirconium silicate is often easier to
disperse well in a glaze. Zirconia is said to give better whites
because of the lack of silica or resulting lower level of silica in
the glaze.
I'm not sure one can easily find zirconia in pottery supply houses
today--but I haven't done a big search for it.
Regards,
John
Tom Buck on thu 10 nov 05
Steve S:
The zirconium opacifiers, ZrO2 (oxide) and ZrSiO4
(silicate/zircon) do NOT melt in any alumino-silicate mix we use in our
glazes. these two have melting points above 2700 degrees Celsius 4860
degrees Fahrenheit. and do not dissolve in the Liquidus; they remain in
suspension. We use these opacifiers as very fine powders, sub-micron, and
either will yield a "white" glaze because the particle size is in the
range that reflects light at an appropriate wave-length.
good pots peace Tom B.
Tom Buck ) -- primary address.
"alias" or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada
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