Tom Buck on fri 1 oct 99
Why omit Zinc Oxide? Because when you reduce a lot, the ZnO goes to Zn
metal and boils off. In some cases there is no zinc oxide left in the
glaze. David H. in Texas ran some Copper Red tests, ones with ZnO in the
RCP, ones without. He reported on Clayart that his Cu red came out exactly
the same, the ZnO had departed. However, if your Cu Red starts out as
being quite viscous at C10 the ZnO (before it departs) might lower the
viscosity enough to allow good copper oxide reduction, and hence good
reds. As David noted, using ZnO in C10R glazes is simply wheel-spinning
most of the time, and hence a waste of cash.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Ron Roy on mon 4 oct 99
See David's article in this months CM on the subject - most revealing.
I wish there were more articles on glazes that were as well designed as
this one. The truth is obvious - well done David.
RR
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Andrew Buck on sun 17 oct 99
Tom,
If I read your post right, then, sometime zinc oxide might be useful in
some cone 10 reduction glazes. It seems to be a good assumption that, to
see if the glaze one is using needs zinc oxide, one needs to test, in the
same glaze loads, a sample of glaze with and without, as David did. If
the glaze comes out better with the zinc, use it. If there is no
difference or the glaze is better with out, then don't put any in and save
money. If it doesn't do anything but burn out, one would not even have to
recalculate the glaze. Just omit the zinc oxide. Seems a relatively easy
test to do.
Andy Buck
Raincreek Pottery
Port Orchard, Washington
On Fri, 1 Oct 1999, Tom Buck wrote:
> ----------------------------Original message----------------------------
> Why omit Zinc Oxide? Because when you reduce a lot, the ZnO goes to Zn
> metal and boils off. In some cases there is no zinc oxide left in the
> glaze. David H. in Texas ran some Copper Red tests, ones with ZnO in the
> RCP, ones without. He reported on Clayart that his Cu red came out exactly
> the same, the ZnO had departed. However, if your Cu Red starts out as
> being quite viscous at C10 the ZnO (before it departs) might lower the
> viscosity enough to allow good copper oxide reduction, and hence good
> reds. As David noted, using ZnO in C10R glazes is simply wheel-spinning
> most of the time, and hence a waste of cash.
>
> Tom Buck )
Ray Aldridge on mon 18 oct 99
At 12:15 PM 10/17/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Tom,
>
>If I read your post right, then, sometime zinc oxide might be useful in
>some cone 10 reduction glazes. It seems to be a good assumption that, to
>see if the glaze one is using needs zinc oxide, one needs to test, in the
>same glaze loads, a sample of glaze with and without, as David did. If
>the glaze comes out better with the zinc, use it. If there is no
>difference or the glaze is better with out, then don't put any in and save
>money. If it doesn't do anything but burn out, one would not even have to
>recalculate the glaze. Just omit the zinc oxide. Seems a relatively easy
>test to do.
>
You might also want to run a test with some other flux replacing the zinc.
I quit using zinc just because it was such a pain in the ass to sieve, and
because it has a bad effect on a lot of stains. But I replaced it in
several glazes by increasing the calcium slightly, or replaced it with
strontium carbonate (expensive solution, but there's usually not a lot of
zinc in high temp glazes.)
In any case, the point I'm struggling to make is that even if the glaze
isn't as good when the zinc is left out, that doesn't mean you can't get
rid of the zinc anyway, if you're willing to experiment a little with
another auxiliary flux.
Ray
Aldridge Porcelain and Stoneware
http://www.goodpots.com
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