Gene and Dolita Dohrman on tue 28 oct 03
Today my friend and I unloaded a Cone 10 reduction firing. I was very =
excited as I had three pieces in the kiln. We pulled out her bowls and =
they were beautiful, the blues and greens swirled and had such depth, =
the gloss was so amazing that peering into her bowls looked almost like =
an optical illusion-my eyes kept trying to focus. So I got a little =
excited, thinking, wow, mine must look this good also. Well, they were =
stoneware and looked like crap. They were bubbled and out of nowhere I =
got this nasty brown and gold, a little of the blue and green but not =
enough. My friend offered to take them home with her and fire them to =
Cone 10 in her electric kiln. I tried to talk her out of it but she =
insisted. We will see what happens. Now I know why people love =
porcelain-the glazes are breath taking. Even my belly button pitcher, =
as I like to call it, looked like crap and that was a Tenmoku glaze. I =
have three porcelain pieces glazed in Tenmoku out of the last firing =
that worked perfectly. As I have said before, ya live, ya learn. I am =
sure you have all discussed this before and there were recent threads on =
what grog in the claybody does to glazes. What exactly do you add to a =
glaze to make it work better on stoneware? It is very obvious to me =
that you cannot use the same glaze on stoneware as on porcelain.=20
Dolita-getting out the hammer....=20
dohrman@insightbb.com
Louisville, KY
Rob Van Rens on wed 29 oct 03
Dolita,
You can, in fact, use the same glazes on stoneware and porcelain. You'll
just get different effects. I use a number of slip-and-ash-based glazes
that work well on both types of clay; the effects are just VERY different.
One perfect example is my Cone 8 Amber (oxidation); on porcelain, which I
originally developed it for, it's a nice, pale iron amber, which fades on
the high points and does bubbles a little bit at the foot ring, providing a
nice counterpoint...on the other hand, when I use it on a iron-bearing
stoneware, it becomes a deep, rich brown, almost an oxidation temmoku, and
it makes the grog in the stoneware stand out as golden flecks. It's still
really cool, but it's not AT ALL the same effect.
As has been pointed out on this list since time immemorial; test, test test.
Rob Van Rens
Frederick Clay Art Center
5400 Yukon Ct, Unit 500
Frederick, MD 21758
(301) 676-9339
----- Original Message -----
From: "Gene and Dolita Dohrman"
I am sure you have all discussed this before and there were recent threads
on what grog in the claybody does to glazes. What exactly do you add to a
glaze to make it work better on stoneware? It is very obvious to me that
you cannot use the same glaze on stoneware as on porcelain.
Dolita-getting out the hammer....
dohrman@insightbb.com
Louisville, KY
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Hank Murrow on wed 29 oct 03
Dear Dolita;
The iron in your stoneware body is contributing color to the glaze and
if you reduce the colorant laod in your glaze to compensate, you may be
surprised by a different and more pleasing result. Correspondingly,
sometimes glazes need to have the colorant loads increased when used on
porcelain.
Good Luck, Hank in Eugene
On Tuesday, October 28, 2003, at 08:56 PM, Gene and Dolita Dohrman
wrote:
> Today my friend and I unloaded a Cone 10 reduction firing. I was very
> excited as I had three pieces in the kiln. We pulled out her bowls
> and they were beautiful, the blues and greens swirled and had such
> depth, the gloss was so amazing that peering into her bowls looked
> almost like an optical illusion-my eyes kept trying to focus. So I
> got a little excited, thinking, wow, mine must look this good also.
> Well, they were stoneware and looked like crap. They were bubbled and
> out of nowhere I got this nasty brown and gold, a little of the blue
> and green but not enough. My friend offered to take them home with
> her and fire them to Cone 10 in her electric kiln. I tried to talk
> her out of it but she insisted. We will see what happens. Now I know
> why people love porcelain-the glazes are breath taking. Even my belly
> button pitcher, as I like to call it, looked like crap and that was a
> Tenmoku glaze. I have three porcelain pieces glazed in Tenmoku out of
> the last firing that worked perfectly. As I have said before, ya
> live, ya learn. I am sure you have all discussed this before and
> there were recent threads on what grog in the claybody does to glazes.
> What exactly do you add to a glaze to make it work better on
> stoneware? It is very obvious to me that you cannot use the same
> glaze on stoneware as on porcelain.
> Dolita-getting out the hammer....
Bobbruch1@AOL.COM on thu 30 oct 03
<<<< Dolita writes: As I have said before, ya live, ya learn. I am sure you
have all discussed this before and there were recent threads on what grog in
the claybody does to glazes. What exactly do you add to a glaze to make it
work better on stoneware?
Sometimes, it is what you put under it, or over it. I use a heavily grogged
body at cone 6 ox, and I find that slips (several of which you will find in
the archives) and store bought underglazes of various colors will have a
different effect on each of your range of glazes. In general, I find that glazes
which look great with porcelain do nothing on stoneware and vica versa, at least
in oxidation. Underglaze coatings in the white and even yellow range can
modify some glazes to give a porcelain type of response. But, for the most part,
you are going to have to test, test, and test again. You might put a light and
dark underglaze or slip on each test tile along with leaving space for the
original clay body to see the differences.
<<< It is very obvious to me that you cannot use the same glaze on stoneware
as on porcelain. Dolita-getting out the hammer....
Before you use the hammer......... try putting a glaze over what you have. I
think you said you got some bubbling, so you might want to knock the bubbles
off with a dremel tool - using goggles and a mask. You might get some
interesting results with another cone 10 glaze over it, fired at either reduction or
oxidation, or try a cone 6 glaze on top fired in an electric kiln. I sometimes
use runny glazes (ash) and get decent results about 1/3 of the time. If there
were lots of bubbles which you can get off with a dremel, then go to a lower
firing temperature so as not to repeat the process of creating even more
bubbles.
Bob Bruch
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