Janet Starr on sat 25 nov 06
Dear Ron & Roy,
So, I have been using Glazemaster after a workshop and I put all my glazes
into the software. Some came up very high on the COE, but they all look
nice and I'm making tile, not dinner ware, so it works for me . But one
glaze, a burgundy has a little crazing sometimes and I thought I would try
and fix it. I followed the directions to decrease the sodium and potassium
and increase the magnesium and boron. All the other components remained the
same and I thought this would really work! The COE went from 524.7 to 424.3.
The only chemical I changed was substituting talc for whiting and
adjustments in the quantities of the rest. Instead of burgundy, I got a
light grey with a hint of lavendar. Why is this? I fire to Cone 3
oxidation. The Al2O3 for both was 2.3, and the SiO2 was 2.6. Do you have
any suggestions as to how to make this right? Why did the color go away?
Original New
Kona 26.0 Kona 18.5
Frit 3134 32.0 3134 37.0
Silica 19.0 Silica 13.5
Ball Clay 5.0 Ball Clay 8.0
EPK 5.0 EPK 8.0
Whiting 13.0 Talc 15.0
Mason Stain 6381 - 6.0 in each sample
SiAL 11.39 SiAL: 11.31
COE 524.70 COE 424.30
LOI 7.18 LOI 3.03
I don't understand why colorants are not included in glaze calculation. It
seems that they do make a big difference. I tried another test in which I
added 6.0 of Zircopax and a total of 8.0 mason stain 6381 to the original
recipe and that sample came out burgundy and with less crazing than the
original, yet zircopax is not supposed to do anything. I have noticed that
glazes with zircopax tend to craze less than clear glazes.
Any ideas of what I can do with this glaze? Thanks.
Janet
--
Janet Starr
www.craftsmantiles.com
www.featuretile.com
featuretile@gmail.com
John and Judy Hesselberth on sun 26 nov 06
Hi Janet,
The short answer is that you probably moved farther than you needed
to solve the crazing and glaze composition does affect color. Try a
five or 6 part line blend between the original and the new versions
and see if you can find a spot where the color is the same but the
crazing is gone. If not then the next step would be to try some
different materials substitutions that might affect color less.
Volumetric line blends are pretty easy to do and are explained in the
GlazeMaster User's Guide if you haven't done one before.
There is no good answer as to why colors are not included in the
calculations except that we really don't have enough knowledge to
include them in a meaningful way. We often do include iron when we
are looking at reduction glazes because there it has a big effect.
I hope this helps. You are making a good start and I think if you
will do the line blend you will learn a lot about how this glaze
behaves as you substitute magnesium and boron for sodium and
potassium. I suspect others will have some suggestions also.
Regards,
John
On Nov 25, 2006, at 7:07 PM, Janet Starr wrote:
> Dear Ron & Roy,
>
> So, I have been using Glazemaster after a workshop and I put all my
> glazes
> into the software. Some came up very high on the COE, but they all
> look
> nice and I'm making tile, not dinner ware, so it works for me . But
> one
> glaze, a burgundy has a little crazing sometimes and I thought I
> would try
> and fix it. I followed the directions to decrease the sodium and
> potassium
> and increase the magnesium and boron. All the other components
> remained the
> same and I thought this would really work! The COE went from 524.7
> to 424.3.
> The only chemical I changed was substituting talc for whiting and
> adjustments in the quantities of the rest. Instead of burgundy, I
> got a
> light grey with a hint of lavendar. Why is this? I fire to Cone 3
> oxidation. The Al2O3 for both was 2.3, and the SiO2 was 2.6. Do
> you have
> any suggestions as to how to make this right? Why did the color go
> away?
>
> Original New
> Kona 26.0 Kona 18.5
> Frit 3134 32.0 3134 37.0
> Silica 19.0 Silica 13.5
> Ball Clay 5.0 Ball Clay 8.0
> EPK 5.0 EPK 8.0
> Whiting 13.0 Talc 15.0
>
> Mason Stain 6381 - 6.0 in each sample
>
> SiAL 11.39 SiAL: 11.31
> COE 524.70 COE 424.30
> LOI 7.18 LOI 3.03
>
> I don't understand why colorants are not included in glaze
> calculation. It
> seems that they do make a big difference. I tried another test in
> which I
> added 6.0 of Zircopax and a total of 8.0 mason stain 6381 to the
> original
> recipe and that sample came out burgundy and with less crazing than
> the
> original, yet zircopax is not supposed to do anything. I have
> noticed that
> glazes with zircopax tend to craze less than clear glazes.
>
> Any ideas of what I can do with this glaze? Thanks.
>
> Janet
>
> --
> Janet Starr
> www.craftsmantiles.com
> www.featuretile.com
> featuretile@gmail.com
>
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Ron Roy on sun 26 nov 06
Hi Janet,
The chrome/tin pinks and reds can be tricky - that is where part of the
colour is coming from - probably - in this case - because you added MgO.
Slow cooling helps this kind of colour by the way - you may find refiring
in a bisque firing will get the colour back - if that works you will know
that a slower cool with work as well.
I just looked up that stain in Tuckers catalogue and there are specific
conditions for that stain to work - no zinc, Maximum temp. is 2300F and
glaze must contain 6.7 to 8.4% CaO
You took out a lot of CaO so that probably explains it.
I would try subbing in Li20 for KNaO - it has a much lower expansion rate -
but has a similar effect on glazes - you can keep everything else the same
that way.
I used the Aussi Spod - there are others depending what you can get but it
is worth a try - here is my revision with a little more CaO and a much
lower expansion.
AUSSI SPOD........... 16.00
F3134............... 32.00
WHITING............. 14.00
OM-4................ 4.50
EPK................. 8.00
SILICA.............. 25.50
----------
100.00
FORMULA & ANALYSIS
------------------
*CaO........ .72
MnO2....... .00
*Li2O....... .12
*MgO........ .00
*K2O........ .00
*Na2O....... .15
Fe2O3...... .00
TIO2....... .00
B2O3....... .30
AL2O3...... .24
SiO2....... 2.71
P2O5....... .00
RATIO 11.32 (original is 11.41)
EXPAN 411.01 (original is 524.7))
WEIGHT 262.78
RR
>Dear Ron & Roy,
>
>So, I have been using Glazemaster after a workshop and I put all my glazes
>into the software. Some came up very high on the COE, but they all look
>nice and I'm making tile, not dinner ware, so it works for me . But one
>glaze, a burgundy has a little crazing sometimes and I thought I would try
>and fix it. I followed the directions to decrease the sodium and potassium
>and increase the magnesium and boron. All the other components remained the
>same and I thought this would really work! The COE went from 524.7 to 424.3.
>The only chemical I changed was substituting talc for whiting and
>adjustments in the quantities of the rest. Instead of burgundy, I got a
>light grey with a hint of lavendar. Why is this? I fire to Cone 3
>oxidation. The Al2O3 for both was 2.3, and the SiO2 was 2.6. Do you have
>any suggestions as to how to make this right? Why did the color go away?
>
>Original New
>Kona 26.0 Kona 18.5
>Frit 3134 32.0 3134 37.0
>Silica 19.0 Silica 13.5
>Ball Clay 5.0 Ball Clay 8.0
>EPK 5.0 EPK 8.0
>Whiting 13.0 Talc 15.0
>
>Mason Stain 6381 - 6.0 in each sample
>
>SiAL 11.39 SiAL: 11.31
>COE 524.70 COE 424.30
>LOI 7.18 LOI 3.03
>
>I don't understand why colorants are not included in glaze calculation. It
>seems that they do make a big difference. I tried another test in which I
>added 6.0 of Zircopax and a total of 8.0 mason stain 6381 to the original
>recipe and that sample came out burgundy and with less crazing than the
>original, yet zircopax is not supposed to do anything. I have noticed that
>glazes with zircopax tend to craze less than clear glazes.
>
>Any ideas of what I can do with this glaze? Thanks.
>
>Janet
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
stephani stephenson on mon 27 nov 06
changes in Alumina/ silica ratio may also affect
color in surprising ways.
Stephani Stephenson
revivalsteph[use@]yahoo.com
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