Otto Wenger on wed 6 jan 10
I have been working on using a new glaze for me. Turquoise matte ^6. When=
=3D
the pots reached a temperature that could be handled I removed them from =
=3D
the
kiln and brought them into the kitchen. Before you know it it sounded lik=
=3D
e a
set of wind chimes blowing in the breeze. They were pinging like crazy. I=
=3D
expect this is from poor glaze fit. The pinging has stopped and there is =
=3D
no
visible sign of crazing. I checked the coeffecient of expansion with my
glaze software Matrix. The COE according to Matrix is 8.17. Is that high?=
=3D
What should my goal for a COE be?
Below is the glaze formula
Nepheline Syenite 61.54
Strontium carbonate 20.88
Ball clay 6.59
Silica 7.69
Lithium carbonate 3.30
Copper carbonate 3.50
Bentonite 4.00
Any advice on improving the fit on this glaze would be appreciated.
Ron Roy on wed 6 jan 10
Hi Otto,
Yes the expansion is very high - typical for any glaze with that much
Neph Sy or feldspar - but the alkalies are what you need to get that
colour.
If you have some spodumene it may be possible to get the expansion
down enough to stop the crazing.
Tell me what spod you can get and I'll send you some revisions to try.
Let me know what frits you have as well - a little boron should help
the situation.
RR
Quoting Otto Wenger :
> I have been working on using a new glaze for me. Turquoise matte ^6. When
> the pots reached a temperature that could be handled I removed them from =
the
> kiln and brought them into the kitchen. Before you know it it sounded lik=
e a
> set of wind chimes blowing in the breeze. They were pinging like crazy. I
> expect this is from poor glaze fit. The pinging has stopped and there is =
no
> visible sign of crazing. I checked the coeffecient of expansion with my
> glaze software Matrix. The COE according to Matrix is 8.17. Is that high?
> What should my goal for a COE be?
> Below is the glaze formula
>
> Nepheline Syenite 61.54
> Strontium carbonate 20.88
> Ball clay 6.59
> Silica 7.69
> Lithium carbonate 3.30
> Copper carbonate 3.50
> Bentonite 4.00
>
> Any advice on improving the fit on this glaze would be appreciated.
>
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