Ron Roy on tue 29 sep 98
From time to time I get asked a question about a glaze that changes colour
in use. Just got asked one and thought it would be useful to post it.
Some one left a rotten apple in a pot glazed with the following glaze. This
is a blue glaze but where the apple was it had turned white.
This is a semi-matte cone 5/6 glaze on porcelain.
Those of you who are calculators will see the following when you evaluate
the glaze using cone 6 limit formulas which attempt to predict durability.
ZnO is somewhat over supplied and CaO is low - the significant part is that
silica is way under - the limits I use for glazes without B2O3 say it needs
from 2.5 to 3.5 moles of silica - this glaze has 1.76.
This glaze will craze on any body I am familiar with.
Not a durable glaze - do not apply where it can come in contact with food.
G 200 SPAR.......... 50.00
STRONT CARB......... 22.00
ZINC OXIDE.......... 11.00
SILICA.............. 9.00
WHITING............. 5.00
EPK................. 5.00
*copper carb......... 2.00
*coblt carb.......... 2.00
MnO2................ .05
----------
106.05
FORMULA & ANALYSIS
------------------
*CaO........ .13 3.42%
MnO2....... .00 .05%
*MgO........ .00 .02%
*K2O........ .13 5.79%
*Na2O....... .06 1.63%
*ZnO........ .32 11.95%
Fe2O3...... .00 .09%
TIO2....... .00 .02%
AL2O3...... .26 11.99%
SiO2....... 1.76 48.34%
P2O5....... .00 .01%
*SrO........ .35 16.69%
RATIO 6.86
EXPAN 700.81
WEIGHT 218.76
This was probably a Barium glaze (with approx 27% BaCO3) in which the
Barium has been replaced with Strontium.
Any questions?
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Mark Mondloch on wed 30 sep 98
Hi Ron,
Is there an easy way to convert the expansion figures that you use to the ones
used in Insight? When you make a comment about a glaze's chances of crazing,
I'd like to be able to relate it to the figures I'm familiar with. Thanks.
Sylvia
Ron Roy wrote:
> ----------------------------Original message----------------------------
> >From time to time I get asked a question about a glaze that changes colour
> in use. Just got asked one and thought it would be useful to post it.
>
> Some one left a rotten apple in a pot glazed with the following glaze. This
> is a blue glaze but where the apple was it had turned white.
>
> This is a semi-matte cone 5/6 glaze on porcelain.
>
> Those of you who are calculators will see the following when you evaluate
> the glaze using cone 6 limit formulas which attempt to predict durability.
>
> ZnO is somewhat over supplied and CaO is low - the significant part is that
> silica is way under - the limits I use for glazes without B2O3 say it needs
> from 2.5 to 3.5 moles of silica - this glaze has 1.76.
>
> This glaze will craze on any body I am familiar with.
>
> Not a durable glaze - do not apply where it can come in contact with food.
>
> G 200 SPAR.......... 50.00
> STRONT CARB......... 22.00
> ZINC OXIDE.......... 11.00
> SILICA.............. 9.00
> WHITING............. 5.00
> EPK................. 5.00
> *copper carb......... 2.00
> *coblt carb.......... 2.00
> MnO2................ .05
> ----------
> 106.05
> FORMULA & ANALYSIS
> ------------------
> *CaO........ .13 3.42%
> MnO2....... .00 .05%
> *MgO........ .00 .02%
> *K2O........ .13 5.79%
> *Na2O....... .06 1.63%
> *ZnO........ .32 11.95%
> Fe2O3...... .00 .09%
> TIO2....... .00 .02%
> AL2O3...... .26 11.99%
> SiO2....... 1.76 48.34%
> P2O5....... .00 .01%
> *SrO........ .35 16.69%
>
> RATIO 6.86
> EXPAN 700.81
> WEIGHT 218.76
>
> This was probably a Barium glaze (with approx 27% BaCO3) in which the
> Barium has been replaced with Strontium.
>
> Any questions?
>
> Ron Roy
> 93 Pegasus Trail
> Scarborough, Ontario
> Canada M1G 3N8
> Tel: 416-439-2621
> Fax: 416-438-7849
>
> Web page: http://digitalfire.com/education/people/ronroy.htm
--
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake, WI 53075
mondfam@execpc.com
http://www.execpc.com/~mondfam
Ron Roy on fri 2 oct 98
Hi Sylvia,
Piece of cake!
Here are the expansion numbers I use. Change the values in any glaze
program to these - save them as MDT or TMT or whatever after renaming it
RR's or what ever. In Insight you can then work in what ever version you
want and even swithch back and forth to compare both expansions.
I can only give specific instructions for doing this in Insight and will be
glad to give more detailed instructions - perhaps others can explain how to
do it with other programs.
MDT map using Ron's expansion numbers.
Oxide - Expan
BaO - 14.00
CaO - 16.30
MnO - 2 5.70
Li2O - 7.45
MgO - 4.50
K2O - 39.00
Na2O - 41.60
ZnO - 7.00
Fe2O3 - 10.40
TiO2 - 10.60
B2O3 - -6.53 yes! that is a minus
Al2O3 - 1.40
SiO2 - 0.50
PbO - 10.60
P2O5 - 7.45
SnO2 - 3.65
ZrO2 - 2.30
SrO - 13.50
>----------------------------Original message----------------------------
>Hi Ron,
>Is there an easy way to convert the expansion figures that you use to the ones
>used in Insight? When you make a comment about a glaze's chances of crazing,
>I'd like to be able to relate it to the figures I'm familiar with. Thanks.
>Sylvia
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
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