Shelley S on thu 27 nov 97
Hi Group,
Just out of curiosity - a woman in our studio was asking about how to
eliminate the crazing of a Coleman purple glaze on white stoneware. Among
other possibilities, would she be able to just drop the barium to lower the
expansion or would this also affect the color response, opacity, etc.?
Coleman Purple Maroon - C 8-10 reduction
Custer 49.26
Silica 24.63
Whiting 7.88
Dolomite 4.93
Gerstley Borate 4.93
Barium Carb 4.93
Zinc Oxide 2.46
Tin Oxide 0.99
Copper Carb 2.0
Cobalt Carb .24
thanks for your input.
Shelley
Nils Lou on fri 28 nov 97
In similar glazes I have eliminated crazing by increasing the silica--as
much double. Nils
On Thu, 27 Nov 1997, Shelley S wrote:
> ----------------------------Original message----------------------------
> Hi Group,
>
> Just out of curiosity - a woman in our studio was asking about how to
> eliminate the crazing of a Coleman purple glaze on white stoneware. Among
> other possibilities, would she be able to just drop the barium to lower the
> expansion or would this also affect the color response, opacity, etc.?
>
> Coleman Purple Maroon - C 8-10 reduction
>
> Custer 49.26
> Silica 24.63
> Whiting 7.88
> Dolomite 4.93
> Gerstley Borate 4.93
> Barium Carb 4.93
> Zinc Oxide 2.46
> Tin Oxide 0.99
>
> Copper Carb 2.0
> Cobalt Carb .24
>
> thanks for your input.
>
> Shelley
>
Ray Carlton on fri 28 nov 97
hi shelley try increasing the silica in 1% increments [line blend starting
at silica 24 up to say 34] If you need to know how a line blend works email me
cheers
At 10:27 27/11/97 EST, you wrote:
>----------------------------Original message----------------------------
>Hi Group,
>
>Just out of curiosity - a woman in our studio was asking about how to
>eliminate the crazing of a Coleman purple glaze on white stoneware. Among
>other possibilities, would she be able to just drop the barium to lower the
>expansion or would this also affect the color response, opacity, etc.?
>
>Coleman Purple Maroon - C 8-10 reduction
>
>Custer 49.26
>Silica 24.63
>Whiting 7.88
>Dolomite 4.93
>Gerstley Borate 4.93
>Barium Carb 4.93
>Zinc Oxide 2.46
>Tin Oxide 0.99
>
>Copper Carb 2.0
>Cobalt Carb .24
>
>thanks for your input.
>
>Shelley
>
>
raycarlt@valylink.net.au
Ray Carlton
McMahons Creek Victoria Australia 3799
David Hewitt on sat 29 nov 97
Using English & Turner coefficients, this glaze has a calculated
coefficient of expansion of 5.35 x 10-6 /oC linear
If you leave out the barium carbonate this becomes 4.97 x 10-6 /oC
linear.
It is, therefore, moving in the right direction to reduce crazing, but
it could well alter the colour response etc.. Only by testing would you
be able to tell if this is enough to overcome the crazing and if the
degree of any colour change etc. creates another problem.
In message , Shelley S writes
>----------------------------Original message----------------------------
>Hi Group,
>
>Just out of curiosity - a woman in our studio was asking about how to
>eliminate the crazing of a Coleman purple glaze on white stoneware. Among
>other possibilities, would she be able to just drop the barium to lower the
>expansion or would this also affect the color response, opacity, etc.?
>
>Coleman Purple Maroon - C 8-10 reduction
>
>Custer 49.26
>Silica 24.63
>Whiting 7.88
>Dolomite 4.93
>Gerstley Borate 4.93
>Barium Carb 4.93
>Zinc Oxide 2.46
>Tin Oxide 0.99
>
>Copper Carb 2.0
>Cobalt Carb .24
>
>thanks for your input.
>
>Shelley
>
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- +44 (0) 1633 420647
URL http://digitalfire.com/education/people/hewitt.htm
| |
|
