SolvejgMa@aol.com on mon 22 apr 96
Hi gang!
I have this beautiful (commercial) purple glaze, Laguna's ^5 Grape. When I
tested it on small bowls at ^6 oxy, all went well, it was tight and smooth
and nary a crack. So, being a trusting sort I put it on one of my best
porcelain "Hungry Gal" bowls, a big big bowl (think popcorn) with moderately
thin walls. (elegant popcorn) Well, after a ^6 firing it cooled for a good
30 hours. I took it out and it proceeded to sing to me for a week. Ping!
Ching! Tink! I smeared it with clay water and could see that the entire bowl
was covered with craze lines. I refired it hotter, same thing. Refired one
more time, cooler, slower and with a clear glaze over the top. (I'll try
anything) Same thing, crazing galore. So, why did the small bowls come out
just fine and the big one craze so badly?
Second question. What glaze ingredient would turn a Hunter Green underglaze
to Grey Pea Soup? I tried using copper stain with this clear glaze
(commercial again) and it did the same thing. Grey yuck! I want to avoid
this when I make my own glazes.
Yes, I've learned my lesson and will be making my own glazes from here on,
but this was an emergency firing. Miracles happen and I ended up with a spot
in a show after all, after being #32 on the waiting list. Sorta caught me
with my potter's pants down...
Thanks for any help!
Kat in Salem, Oregon
** Emily, can't you redirect that rain elsewhere? It's overflowing into the
valley, and I have a house to build! ** :)
Kathy A. Cheriki on tue 23 apr 96
the same thing happened to me with a ^6 white "majolica" glaze. The
taller peices crazed, the shorter ones not. What causes this, who knows,
probably something do with gravity?
Kent Van Cleave on wed 24 apr 96
>Why did the small bowls come out just fine and the big one craze so badly?
Perhaps the clay body is at fault. Some Glazes are not friendly with porcelain.
>Second question. What glaze ingredient would turn a Hunter Green underglaze
>to Grey Pea Soup?
Underglazes turn different colors when they are overfired. Did you? The
Duncan color charts show this washout. Also, try using a zinc-free clear
over it. The zinc changes a lot of underglazes in the C5 -- C6 range.
Bill Buckner on wed 24 apr 96
Kat:
Does that clear glaze contain zinc? It may be the culprit in causing the
unexpected color change in your underglazes. Since you are using a
"commercial" clear glaze, see if you can find another labelled
"zinc-free."
-Bill
Bill Buckner e-mail: bbuckner@gsu.edu
Georgia State University http://www.gsu.edu/~couwbb
On Mon, 22 Apr 1996 SolvejgMa@aol.com wrote:
> Second question. What glaze ingredient would turn a Hunter Green underglaze
> to Grey Pea Soup? I tried using copper stain with this clear glaze
> (commercial again) and it did the same thing. Grey yuck! I want to avoid
> this when I make my own glazes.
Leona Stonebridge Arthen on mon 29 apr 96
At 10:56 PM 4/22/96, SolvejgMa@aol.com wrote:
>----------------------------Original message----------------------------
>... Laguna's ^5 Grape. When I
>tested it on small bowls at ^6 oxy, all went well, it was tight and smooth
>and nary a crack.... I put it on ...a big big bowl... with moderately
>thin walls.... So, why did the small bowls come out
>just fine and the big one craze so badly?
Would the size of the pot be having an effect? I notice that glazes look
quite different on the inside and outside of pots due to the way they
"stretch" over the clay's shape. Maybe there is a difference in stretch
between a large and a small pot that would cause such a change in the glaze
that it would craze over the large but not the small pots.???
Leona
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