Dave Kuilema on thu 14 aug 97
Hello All,
Today I mixed up a great new glaze--"superglaze", submitted some
time ago to the list. One of the ingedients is zinc oxide. For years I
have avoided glazes w/ zinc because it is always a problem to get it
through the sieve. I do not have access to a ball mill and trying to grind
w/ a spatula or mortar is time consuming and usually I give up before all
of it has gone through. If it stays in those hard little hunks in the glaze
they end up looking like little white pieces of junk on the pots.
Am I doing something (obvious) wrong?? Can I calcine zinc to make
it behave and disperse in the glaze? If so, will the weight % change in the
batch formula?
The zinc I have has gone through many bouts of humid Michigan
summers, and despite living in a plastic bag w/ a twistie, and inside a
bucket too yet, it is lumpy and hard. It is vintage zinc. In fact, it may
be antique zinc, maybe part of an old retired potter's studio buy-out. Will
fresh zinc solve this problem? Will I find true happiness without zinc in
my future.
Oh great glaze masters of the clayart list- please give me a clue.
Mary
David Hendley on fri 15 aug 97
Yes, fresh zinc will solve the problem. I bought a 50 lb. bag in the 70's
(that's a lot of zinc for a single studio potter) and had to resort to ball
milling to use the last of it a few years ago. Bought a new bag and it's
smooth as any other glaze material. I do think it has to do with moisture
absorbtion over the years
David Hendley
Maydelle, Texas.
At 10:53 AM 8/14/97 EDT, you wrote:
>----------------------------Original message----------------------------
>Hello All,
> Today I mixed up a great new glaze--"superglaze", submitted some
>time ago to the list. One of the ingedients is zinc oxide. For years I
>have avoided glazes w/ zinc because it is always a problem to get it
>through the sieve. I do not have access to a ball mill and trying to grind
>w/ a spatula or mortar is time consuming and usually I give up before all
>of it has gone through. If it stays in those hard little hunks in the glaze
>they end up looking like little white pieces of junk on the pots.
> Am I doing something (obvious) wrong?? Can I calcine zinc to make
>it behave and disperse in the glaze? If so, will the weight % change in the
>batch formula?
> The zinc I have has gone through many bouts of humid Michigan
>summers, and despite living in a plastic bag w/ a twistie, and inside a
>bucket too yet, it is lumpy and hard. It is vintage zinc. In fact, it may
>be antique zinc, maybe part of an old retired potter's studio buy-out. Will
>fresh zinc solve this problem? Will I find true happiness without zinc in
>my future.
>Oh great glaze masters of the clayart list- please give me a clue.
>
>Mary
>
>
James Dapogny on fri 15 aug 97
Hi Mary,
One thing I have done with zinc is to buy one of those little $20 coffee
grinders and use it for zinc, cornwall stone, bone ash, etc. It does a
great job and was well worth the investment.
Good luck from a fellow over-heated Michiganian. Gail Dapogny in Ann Arbor
>----------------------------Original message----------------------------
>Hello All,
> Today I mixed up a great new glaze--"superglaze", submitted some
>time ago to the list. One of the ingedients is zinc oxide. For years I
>have avoided glazes w/ zinc because it is always a problem to get it
>through the sieve. I do not have access to a ball mill and trying to grind
>w/ a spatula or mortar is time consuming and usually I give up before all
>of it has gone through. If it stays in those hard little hunks in the glaze
>they end up looking like little white pieces of junk on the pots.
> Am I doing something (obvious) wrong?? Can I calcine zinc to make
>it behave and disperse in the glaze? If so, will the weight % change in the
>batch formula?
> The zinc I have has gone through many bouts of humid Michigan
>summers, and despite living in a plastic bag w/ a twistie, and inside a
>bucket too yet, it is lumpy and hard. It is vintage zinc. In fact, it may
>be antique zinc, maybe part of an old retired potter's studio buy-out. Will
>fresh zinc solve this problem? Will I find true happiness without zinc in
>my future.
>Oh great glaze masters of the clayart list- please give me a clue.
>
>Mary
Scott Paulding on sun 25 jul 04
Hello,
Thanks everyone for the advise of spouts :)
I have another question. I've heard that Zinc, at cone 10, in reduction is
useless because it vaporizes. Is this true?
Thanks,
-scott
=====
"I should have been a plumber."
-Albert Einstein
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David Hendley on sun 25 jul 04
Theoretically, zinc vaporizes in a cone 10 reduction firing. I'll leave
it to the scientific types to argue that.
But, I can say with confidence that zinc is not "useless" in certain
cone 10 reduction glazes.
A few years ago, I tested several glazes with significant zinc oxide in
their recipes. I also mixed up batches without the zinc, and fired the
2 variations side-by-side.
For some of the glazes, there was no visible difference, but for others
there was, indeed, a difference between the "with" and "without"
zinc variations. I repeated the tests over another firing, with the
same results.
So, I can't say what the zinc is doing, but, for certain glazes, it
is influencing the fired results.
As the Tony the Canadian Cowboy also says, we'll take the results
of a potter over the theory of a scientist any day of the week.
David Hendley
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
>
> I have another question. I've heard that Zinc, at cone 10, in reduction is
> useless because it vaporizes. Is this true?
>
>
John Hesselberth on mon 26 jul 04
Hi Dave,
There is nothing wrong with the science here at all. It all depends on
when the glaze seals over. If it seals over before the zinc oxide is
reduced to zinc metal then not all the zinc will get reduced. Once a
glaze seals over relatively little reduction happens in the interior of
the glaze.
Regards,
John
On Sunday, July 25, 2004, at 10:12 PM, David Hendley wrote:
> we'll take the results
> of a potter over the theory of a scientist any day of the week.
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
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