pduncan on tue 30 mar 99
I am looking for a clear base glaze to use on some underglazed cone 6
porcelain tiles. I was playing around with a sample of ^6 porcelain and
came up with some nice tiles that could be "keepers" except that every
test of clear base glazes I have tried has just about crazed off the
test tile. Does any one have any suggestions of where to start with a
base glaze that will not craze on a ^6 porcelain body? And a base that
would not affect the underglazes adversely. Thanks for any direction.
Pam in WI
Went to NCECA for Friday only, still had "overload" syndrome when I got
back home! Did not make it to the Clayart Room, next time!
Looking forward to Ron Roy's Glaze Calc Class this July
Bryan on wed 31 mar 99
-----Original Message-----
From: pduncan
To: CLAYART@LSV.UKY.EDU
Date: Tuesday, March 30, 1999 9:20 AM
Subject: Clear Base for Porcelain
>----------------------------Original message----------------------------
>I am looking for a clear base glaze to use on some underglazed cone 6
>porcelain tiles. I was playing around with a sample of ^6 porcelain and
>came up with some nice tiles that could be "keepers" except that every
I am using a glaze that would probably meet your requirements, but after
reading all of the discussion about glazes, leaching, durability, etc, I am
hesitant to recommend it.
I am ready to dry mix another (large) batch, but before I do I'd like some
feed back from a glaze person. Did I do the molecular equivalents right... I
modified this from an earlier glaze that was over fired, by adding more
imsil and kona. Could I change my recipe to get the same +/- glaze?
Bryan's Clear #46v121
recipe %
Imsil 38 .314
Gerstley borate 25 .207
Neph. Syenite 25 .207
Wollastonite 15 .124
EPK 10 .083
Kona Fspar 8 .066
K20 .091 Al2O3 .415
Na2o .193 B2O3 .849
CaO .716
SiO2 3.18
Thanks,
Bryan
C.Harris on thu 1 apr 99
Pam,
This is the clear glaze that I use over reward/amaco velvet underglazes
fired to cone 6 oxidation. I have never had any crawling, pinholing or
other problems with tiles, bowls or whatever - and I use underglazes ALL
the time! You may be putting the underglaze on too thick if the clear is
crawling off - or if you are using stains watch the thickness as well.
Here's the recipe - It works on my MCS porcelain clay body with no problem.
Transparent Glaze (% - adds up to 101%, I know)
Frit 3134 50 We have also tested with F12 and works ok
EPK 30
Silica Flint 20
Bentonite 1
Clear glaze should be put on relatively THIN.
Cathy Harris
Potter's Pleasure
Aurora, Ontario
c.harris@aci.on.ca
----------
> From: pduncan
> To: CLAYART@LSV.UKY.EDU
> Subject: Clear Base for Porcelain
> Date: Tuesday, March 30, 1999 10:20 AM
>
> ----------------------------Original message----------------------------
> I am looking for a clear base glaze to use on some underglazed cone 6
> porcelain tiles. I was playing around with a sample of ^6 porcelain and
> came up with some nice tiles that could be "keepers" except that every
> test of clear base glazes I have tried has just about crazed off the
> test tile. Does any one have any suggestions of where to start with a
> base glaze that will not craze on a ^6 porcelain body? And a base that
> would not affect the underglazes adversely. Thanks for any direction.
> Pam in WI
> Went to NCECA for Friday only, still had "overload" syndrome when I got
> back home! Did not make it to the Clayart Room, next time!
> Looking forward to Ron Roy's Glaze Calc Class this July
Mason Batchelder on thu 1 apr 99
I have been in pottery since 1966 and have no familiarity with Imsil and quite
a number of the ingredients in the current issue of Ceramics monthly's
published receipes.Would anyone who is submitting and publishing these
receipes explain any unfamiliar or new ingredients and list the probable
suppliers? please ????
Bryan on fri 2 apr 99
-
>I have been in pottery since 1966 and have no familiarity with Imsil and
quite
>a number of the ingredients in the current issue of Ceramics monthly's
>published receipes.Would anyone who is submitting and publishing these
>receipes explain any unfamiliar or new ingredients and list the probable
>suppliers? please ????
Bryan's Clear #46v121
recipe %
Silica,Amorphous (Imsil) 38 .314
Gerstley borate 25 .207
Neph. Syenite 25 .207
Wollastonite 15 .124
EPK 10 .083
Kona Fspar 8 .066
K20 .091 Al2O3 .415
Na2o .193 B2O3 .849
CaO .716
SiO2 3.18
Sorry for the assumption that Imsil is a common material. It was Air Floated
Silica from Illinois Minerals. The bag now says that it is from UNIMIN. I
got it from A.R.T. , sold as Amorphous Silica, with the product description
"There are no quartz phase changes of amorphous silica during firing,
therefore silica conversions from one phase to another are avoided...no
definite melting point..." (I started using it when Nick Nero was still
doing goofy ads in CM.)
Wollastonite is calcium silicate.
Bryan
Ron Roy on mon 5 apr 99
Hi Bryan,
Here is my print out of your glaze - I am assuming Imsil is silica. Looks
like your analysis of Gerstley Borate is not a true representative - I'm
including the one I use - from H&G
-----------------
SILICA.............. 38.00
Gers Borate 9/97.... 25.00
NEPH SY............. 25.00
WOLAST.............. 15.00
EPK................. 10.00
F4 SPAR............. 8.00
----------
Total 121.00
FORMULA & ANALYSIS
------------------
*CaO........ .64 10.30%
*MgO........ .10 1.19%
*K2O........ .05 1.50%
*Na2O....... .21 3.70%
Fe2O3...... .00 .22%
TIO2....... .00 .03%
B2O3....... .31 6.30%
AL2O3...... .36 10.63%
SiO2....... 3.82 66.11%
P2O5....... .00 .01%
RATIO 10.57
EXPAN 395.20
WEIGHT 346.28
From H&G received Aug 97. Ger Borate.
B2O3 - 27.68
Na2O - 4.29
SiO2 - 11.73
Fe2O3 - 0.48
Al2O3 - 1.63
MgO - 4.19
CaO - 19.06
K2O - 0.1.38
H2O - 5.71
LOI - 23.64 (Last two added together for LOI of 5.71+23.64=29.35)
Total - 98.79
I think this glaze will prove to be safe - depending on how much and what
kind of underglaze it covers - or how much colouring oxides or satins are
mixed in it. I certainly would not recommend any underglaze with Cadmium in
it to be on food bearing surfaces.
RR
>>----------------------------Original message----------------------------
>>I am looking for a clear base glaze to use on some underglazed cone 6
>>porcelain tiles. I was playing around with a sample of ^6 porcelain and
>>came up with some nice tiles that could be "keepers" except that every
>
>
>I am using a glaze that would probably meet your requirements, but after
>reading all of the discussion about glazes, leaching, durability, etc, I am
>hesitant to recommend it.
>
> I am ready to dry mix another (large) batch, but before I do I'd like some
>feed back from a glaze person. Did I do the molecular equivalents right... I
>modified this from an earlier glaze that was over fired, by adding more
>imsil and kona. Could I change my recipe to get the same +/- glaze?
>
>Bryan's Clear #46v121
> recipe %
>Imsil 38 .314
>Gerstley borate 25 .207
>Neph. Syenite 25 .207
>Wollastonite 15 .124
>EPK 10 .083
>Kona Fspar 8 .066
>
>
>K20 .091 Al2O3 .415
>Na2o .193 B2O3 .849
>CaO .716
>
>
> SiO2 3.18
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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