Carolynn Palmer on tue 20 oct 98
I am certainly hoping that everyone who addresses your problem answers you on
the list. Ever since opening a new bag of Gerstley Borate I am having these
same difficulties with my favorite white glaze which uses zircopax or superpax
for the opacifier. I don't have any of the old Gerstley Borate left, so I
cannot go back to using it to see if that is causing the problem for sure.
Carolynn Palmer, Somerset Center, Michigan
Greg Lamont on tue 20 oct 98
At 09:46 AM 10/20/98 EDT, you wrote:
>----------------------------Original message----------------------------
>I am certainly hoping that everyone who addresses your problem answers you on
>the list. Ever since opening a new bag of Gerstley Borate I am having these
>same difficulties with my favorite white glaze which uses zircopax or
superpax
>for the opacifier. I don't have any of the old Gerstley Borate left, so I
>cannot go back to using it to see if that is causing the problem for sure.
>
>Carolynn Palmer, Somerset Center, Michigan
>
Hi Carolynn,
I replied in an earlier postto the original message that should appear
later today on the list. It definitely sounds like your Gerstley Borate is
the source of your troubles here. I had a problem a while back witha glaze
that used a high amount of GB. I solved it by altering the recipe to use a
boron frit (Ferro #3134) for a portion of the GB and it solved the problem
quite nicely. Here are the original and the revised recipes:
Clear Gloss Base Cone 5-6 Ox. (original)
Nepheline syenite 47.3
Gerstley borate 27
Flint 20.3
EPK 5.4
Clear Gloss Base Cone 5-6 Ox. (Revised)
Nepheline syenite 41
Gerstley borate 17
Frit 3134 13
Flint 18
EPK 11
Hope this helps.
Regards,
Greg Lamont
3011 Northwood Dr.
Ames, Iowa 50010-4750
515/233-3442
gdlamont@iastate.edu
Ron Roy on wed 21 oct 98
Hi Greg,
Hey you are getting pretty good at this - here are my calculations in case
you want to compare - well done!
Regards - RR
original
-----------------
NEPH SY............. 47.30
Gers Borate 9/97.... 27.00
SILICA.............. 20.30
EPK................. 5.40
----------
100.00
FORMULA & ANALYSIS
------------------
*CaO........ .28 6.13%
*MgO........ .08 1.32%
*K2O........ .07 2.53%
*Na2O....... .26 6.40%
Fe2O3...... .00 .24%
TIO2....... .00 .02%
*B2O3....... .31 8.36% (I calculate this type of glaze with B2O3
in unity)
AL2O3...... .37 14.87%
SiO2....... 2.55 60.13%
P2O5....... .00 .01%
RATIO 6.88
EXPAN 469.69
WEIGHT 254.93
Your variation
-----------------
NEPH SY............. 41.00
Gers Borate 9/97.... 17.00
F3134............... 13.00
SILICA.............. 18.00
EPK................. 11.00
----------
100.00
FORMULA & ANALYSIS
------------------
*CaO........ .31 6.67%
*MgO........ .05 .84%
*K2O........ .06 2.14%
*Na2O....... .27 6.56%
Fe2O3...... .00 .22%
TIO2....... .00 .04%
*B2O3....... .31 8.37%
AL2O3...... .38 15.02%
SiO2....... 2.58 60.14%
P2O5....... .00 .01%
RATIO 6.81
EXPAN 468.05
WEIGHT 257.47
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
Toni Hall on wed 21 oct 98
Carolynn Palmer wrote:...
Carolynn,
I think most of my answers came to me directly, so I'll summerize them for
you and others who might be interested. There were suggestions that the
peeling might be: the components in the glaze itself, application (ie, too
thick or too thin), bisqued too high, glaze that needed more water added to
it, dusty or dirty pots, fired when glaze was wet, or fired too hot or too
fast. I have thanked each individual directly, but will say thank you again
publicly.
I negected to add to my first post that I do sometimes fire the pots with wet
glaze, I bisque to cone 04, fire electric on automatic, and have started
firing on "fast" speed. Therefore, I believe that my problem stems from the
first and the last problem (firing wet glaze and firing too fast). Now I know
where to look for correction.
Good luck with your glaze. Thanks, Toni
Marty Anderson on wed 21 oct 98
I am having the same problem with a glaze I use all the time. The new batch
is coming out with pinholes. I am not sure if the school had opened a new
bag of Gerstley Borate or not. My previous batch was made last semester,
and this batch was made a few weeks ago. I know the school has not changed
their supplier for this chemical. What could be the problem?
Marty
-----Original Message-----
From: Carolynn Palmer
To: CLAYART@LSV.UKY.EDU
Date: Tuesday, October 20, 1998 8:50 AM
Subject: Pinholes and peeling-me too!
>----------------------------Original message----------------------------
>I am certainly hoping that everyone who addresses your problem answers you
on
>the list. Ever since opening a new bag of Gerstley Borate I am having
these
>same difficulties with my favorite white glaze which uses zircopax or
superpax
>for the opacifier. I don't have any of the old Gerstley Borate left, so I
>cannot go back to using it to see if that is causing the problem for sure.
>
>Carolynn Palmer, Somerset Center, Michigan
>
Greg Lamont on thu 22 oct 98
At 01:20 PM 10/21/98 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi Greg,
>
>Hey you are getting pretty good at this - here are my calculations in case
>you want to compare - well done!
>
>Regards - RR
>
>original
>-----------------
>NEPH SY............. 47.30
>Gers Borate 9/97.... 27.00
>SILICA.............. 20.30
>EPK................. 5.40
> ----------
> 100.00
> FORMULA & ANALYSIS
> ------------------
>*CaO........ .28 6.13%
>*MgO........ .08 1.32%
>*K2O........ .07 2.53%
>*Na2O....... .26 6.40%
>Fe2O3...... .00 .24%
>TIO2....... .00 .02%
>*B2O3....... .31 8.36% (I calculate this type of glaze with B2O3
>in unity)
>AL2O3...... .37 14.87%
>SiO2....... 2.55 60.13%
>P2O5....... .00 .01%
>
>RATIO 6.88
>EXPAN 469.69
>WEIGHT 254.93
>
>Your variation
> -----------------
>NEPH SY............. 41.00
>Gers Borate 9/97.... 17.00
>F3134............... 13.00
>SILICA.............. 18.00
>EPK................. 11.00
> ----------
> 100.00
> FORMULA & ANALYSIS
> ------------------
>*CaO........ .31 6.67%
>*MgO........ .05 .84%
>*K2O........ .06 2.14%
>*Na2O....... .27 6.56%
>Fe2O3...... .00 .22%
>TIO2....... .00 .04%
>*B2O3....... .31 8.37%
>AL2O3...... .38 15.02%
>SiO2....... 2.58 60.14%
>P2O5....... .00 .01%
>
>RATIO 6.81
>EXPAN 468.05
>WEIGHT 257.47
>
>>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
>
Hi Ron,
Thanks. I do believe I'm getting the hang of this. One day I'd like to
take your glaze calc course, if it ever gets to the Midwestern U.S. I'll
be watching!
Greg Lamont
3011 Northwood Dr.
Ames, Iowa 50010-4750
515/233-3442
gdlamont@iastate.edu
Ron Roy on mon 26 oct 98
It would be a great help if I could see the recipe - for instance - how
much GB. I need to know anout how you are firing your bisque and glazes -
RR
>----------------------------Original message----------------------------
>I am having the same problem with a glaze I use all the time. The new batch
>is coming out with pinholes. I am not sure if the school had opened a new
>bag of Gerstley Borate or not. My previous batch was made last semester,
>and this batch was made a few weeks ago. I know the school has not changed
>their supplier for this chemical. What could be the problem?
>
>Marty
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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