jim wightman on sun 20 nov 11
I've been testing a number of clear cone 6 glazes and have had terrible
problems with crazing, or having the glaze turn milky. The most recent
glaze I tried is G1214W. I tested it on a piece that fired to cone 5.5 and
it was perfect. I glazed all my pots with it and my kiln fired a bit hotter
to cone 6 and it crazed badly. I'm using Laguna SB (cone 6) clay. Do you
think the increased temperature could have had something to do with it? I
didn't open the kiln until it was completely cool. I've tried the 20 X 5
clear, MC6G clear, commercial Mayco (blistered), and several other recipes.
I've read the posts on Clayart and will test a recipe John Hesselberth
recommended testing, but was wondering if anyone else had any input. A
person I know recommended adding 0.5% gerstley borate to help with crazing.
Would that help?
I have had success with Amaco clear but would prefer to mix my own. I've
posted the recipes below. Thanks!
Karen Nakakihara
Alpine, Texas
G1214W
Wollastonite 10
3134 25
EPK 25
Silica 25
F-4 15
John's recipe
3134 25
F-4 5
Wollastonite 10
EPK 25
flint 30
talc 5
May Luk on sun 20 nov 11
Hello Karen;
If you have difficulties with so many recipes, maybe you can try
different clay. I used to use Standard 182 with grog and it was pesky
with lots of glazes but one.
What clay are you using?
Otherwise, a systematic approach like a Currie Grid or line blends
May
Brooklyn NY
On Sun, Nov 20, 2011 at 10:45 AM, jim wightman wrote=
=3D
:
> I've been testing a number of clear cone 6 glazes and have had terrible
> problems with crazing, or having the glaze turn milky. The most recent
> glaze I tried is G1214W. I tested it on a piece that fired to cone 5.5 an=
=3D
d
> it was perfect. I glazed all my pots with it and my kiln fired a bit hott=
=3D
er
> to cone 6 and it crazed badly. I'm using Laguna SB (cone 6) clay. Do you
> think the increased temperature could have had something to do with it? I
> didn't open the kiln until it was completely cool. I've tried the 20 X 5
> clear, MC6G clear, commercial Mayco (blistered), and several other recipe=
=3D
s.
> I've read the posts on Clayart and will test a recipe John Hesselberth
> recommended testing, but was wondering if anyone else had any input. A
> person I know recommended adding 0.5% gerstley borate to help with crazin=
=3D
g.
> Would that help?
>
> I have had success with Amaco clear but would prefer to mix my own. I've
> posted the recipes below. Thanks!
>
> Karen Nakakihara
> Alpine, Texas
>
> G1214W
>
> Wollastonite =3DA0 =3DA010
> 3134 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA025
> EPK =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 25
> Silica =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA025
> F-4 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 15
>
> John's recipe
>
> 3134 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA025
> F-4 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 5
> Wollastonite =3DA0 =3DA0 10
> EPK =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA025
> flint =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 30
> talc =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA05
>
--=3D20
http://www.artspan.org/artist/mayluk
http://www.ceramicsbrooklyn.com/
Ron Roy on sun 20 nov 11
Hi Jim,
Crazing is not usually that difficult to deal with - especially if the
pattern is wide or the crazing is delayed.
Some clays are better then others by the way so you should try
different clays.
Send me a clear that you like - one with wide spaces between the lines
and I'll adjust it for you.
RR
Quoting jim wightman :
> I've been testing a number of clear cone 6 glazes and have had terrible
> problems with crazing, or having the glaze turn milky. The most recent
> glaze I tried is G1214W. I tested it on a piece that fired to cone 5.5 an=
d
> it was perfect. I glazed all my pots with it and my kiln fired a bit hott=
er
> to cone 6 and it crazed badly. I'm using Laguna SB (cone 6) clay. Do you
> think the increased temperature could have had something to do with it? I
> didn't open the kiln until it was completely cool. I've tried the 20 X 5
> clear, MC6G clear, commercial Mayco (blistered), and several other recipe=
s.
> I've read the posts on Clayart and will test a recipe John Hesselberth
> recommended testing, but was wondering if anyone else had any input. A
> person I know recommended adding 0.5% gerstley borate to help with crazin=
g.
> Would that help?
>
> I have had success with Amaco clear but would prefer to mix my own. I've
> posted the recipes below. Thanks!
>
> Karen Nakakihara
> Alpine, Texas
>
> G1214W
>
> Wollastonite 10
> 3134 25
> EPK 25
> Silica 25
> F-4 15
>
> John's recipe
>
> 3134 25
> F-4 5
> Wollastonite 10
> EPK 25
> flint 30
> talc 5
>
John Britt on mon 21 nov 11
Try these. They are from an article in September Ceramics Monthly entitle=
=3D
d=3D20
"Celadons at Six". Leave out the colorants and see if they fit. :
JOHN=3D92S SATIN BLUE CELADON cone 6 reduction=3D20
6.90=3D09Nepheline Syenite=3D20
29.31=3D09Silica=3D20
20.69=3D09Whiting
25.86=3D09Grolleg Kaolin
17.24=3D09Frit 3195
100.00%
1.00=3D09Tin Oxide=3D20
0.50=3D09Synthetic Red Iron Oxide
Add: 3.00 Synthetic Red Iron Oxide for Lung Chuan (on white stoneware)
=3D20
JOHN=3D92S SATIN BLUE CELADON 2 cone 6 reduction=3D20
19.82=3D09Custer Feldspar=3D20
24.32=3D09Silica=3D20
19.82=3D09Grolleg Kaolin
18.03=3D09Frit 3134
4.50=3D09Wollastonite
4.50=3D09Talc
9.01=3D09Dolomite
100%
1.00=3D09Tin Oxide=3D20
0.50 =3D09Synthetic Red Iron Oxide
Add:=3D20
1.50 Synthetic Red Iron Oxide for Lung Chuan Celadon (on white stoneware)=
=3D
.
If you need any Mastering Cone 6 recipes let me know, but you can find so=
=3D
me=3D20
in the archives:
MC6 GLOSSY CLEAR LINER cone 6=3D20
20.1 Feldspar=3D20
19.1 Ferro 3134=3D20
15. Wollastonite=3D20
20. Clay=3D20
6.01 Talc=3D20
19.01 Silica=3D20
You also know that there is a website:
http://cone6pots.ning.com/
and they have lots of things and you can ask for help there too.
Let me know,
John Britt
John Britt on mon 21 nov 11
Karen,
If you liked that website try this one:
http://wpapotters.blogspot.com/2011/10/cone-6-oxidation-results-group-
8.html
And try this glaze:
ODYSSEY CLEAR =3D09Cone 6
Nepheline Syenite =3D0930
Silica =3D09 =3D0930
Whiting =3D09 =3D0910
EPK Kaolin =3D0910
Gerstley Borate =3D09 20
Bentonite=3D09=3D09 =3D09 2
Johnbrittpottery.com
Ben Shelton on tue 22 nov 11
It sounds like you need to test your clay for its COE. Then you will know t=
=3D
he expansion coefficient of the actual batch of clay you are working with. =
=3D
=3D0A=3D0AIt could be that he clay you are using does not meet the specs th=
e ma=3D
ker intended.=3D0A=3D0ATo test you need to make a a series of glazes with e=
xpan=3D
sion coefficients from low to high. "Mastering Cone Six Glazes" covers this=
=3D
.=3D0AApply these test glazes to tiles made form your clay and fire in the =
sa=3D
me manner you normally fire.=3D0AMark everything carefully and keep good no=
te=3D
s.=3D0A=3D0AWhen you know the coe(coefficientof expansion) of your clay you=
can=3D
then either replace the bad clay or adjust your glaze to fit.=3D0A=3D0AIf =
you =3D
need help with glaze calculations please ask. Many here will help.=3D0A=3D0=
A=3DA0=3D
=3D0ABen
| |
|
