Fabienne Cassman on thu 22 oct 98
------------------
Hello, :)
I have my test tiles out of the kiln, but can't make up my mind. I have
been flipping pages of Rhodes', Hamer=26Hamer's and Hopper's books to no
avail. Can anyone help me?
Here is the recipe:
FM091198 - =5E6 Clear Base for MCS
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D==
3D=3D=3D=3D=3D=3D=3D
WOLLASTONITE........ 7.00
EPK KAOLIN.......... 17.00
FRIT 3134........... 27.00
SILICA.............. 21.50
STRONTIUM CARBONATE. 4.00
CUSTER SPAR......... 23.50
=3D=3D=3D=3D=3D=3D=3D=3D
100.00
I did 2 tiles with the clear base and 4 with colorants in it. I have not
tested them to see how they handle thermal shock (boil/freeze routine)
because I seem to have other problems when I look at the tiles under a X10
magnifier. I suppose my first question would be, should I do it anyway or
wait until after I fix the =5Ffew=5F pinholes and a fair amount of bubbles?
Tile A: +5=25 Tin, +4=25 Cobalt
-Blue=3B Shows pinholes on thicker parts=3B hard to tell elsewhere due to =
dark
color.
Tile B: +10=25 Superpax
-White=3B No apparent defects thick or thin. Best tile with D.
Tile C: +3=25 Lithium, +1=25 Cobalt, +0.5 Nickel
-Variegated transparent blue=3B Traps bubbles and shows pinholes the thicker
it gets.
Tile D: Clear - very thin coats
-Transparent=3B No apparent defects.
Tile E: +3=25 Lithium, +2=25 Copper Carbonate, +1=25 Spanish Red Iron
-Transparent green=3B few long crazing lines only on one side the first =
day=3B
now on the third, the lines have increased.
Tile F: Clear - twice as thick as tile D
-Transparent=3B shows few pinholes on the thick section.
Zinc and Rutile are of no concern. Next, I have ZERO control over the
length of the firing schedule, which seems to be the foremost fix. :( I
use the community college to fire my stuff.
What's left as a feasible fix for me would be to apply the glaze less
thickly=3B tile D seems to suggest that, but why then is my thick white just
fine? Lowering the fusion point seems to be a corollary fix, but superpax
contains no flux. And, tile C shows pinholes everywhere=3B isn't lithium a
flux at this range? It sounds backwards. Is there an explanation for this?
Could I get away with it if I just lowered the fusion point a bit (more
flux)? Or is the thin coat the obvious fix? It sounds rather difficult to
achieve the same thickness on every shape/pot and keep the glaze to the
perfect consistency, too.
Thank you for your time :)
=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=
=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60
Fabienne
Yes, I have learned from my mistakes...
I can reproduce them exactly.
Penny Hosler on fri 23 oct 98
Fabienne,
I sure wish you'd try Tony Hansen's ^6 glossy base glaze (G1214W) -- I've
had wonderful luck with it. No problems at all no matter how I doctor it
up. He maintains these are just starting points, but not for me (so far).
After a lot of testing of various glazes I've decided he's overdue for
sainthood.....
Wollastonite - 10
Frit 3134 - 25
EPK - 25
Flint - 25
Kona F4 Feldspar - 15
http://digitalfire.com/education/glaze/g1214w.htm
(code 6 glossy base, fine-tuned)
http://digitalfire.com/education/glaze/cone6.htm
(the original ^5-7 base glaze - gives pretty good percentages for adding
colorants on page 3) You should really read the whole thing - tells you
exactly how to adjust for various problems, chrome-tin colors, etc)
http://digitalfire.com/education/glaze/g1214z.htm
or a silky matte (satin if you fire it fast)
I've never met the man, but I suspect I'm in the throes of a serious
crush....
Penny in WA
-----Original Message-----
From: Fabienne Cassman
To: CLAYART@LSV.UKY.EDU
Date: Thursday, October 22, 1998 7:13 AM
Subject: Glaze Advice Request For Test Results
----------------------------Original message----------------------------
------------------
Hello, :)
I have my test tiles out of the kiln, but can't make up my mind. I have
been flipping pages of Rhodes', Hamer&Hamer's and Hopper's books to no
avail. Can anyone help me?
Here is the recipe:
FM091198 - ^6 Clear Base for MCS
==========================
3D======
WOLLASTONITE........ 7.00
EPK KAOLIN.......... 17.00
FRIT 3134........... 27.00
SILICA.............. 21.50
STRONTIUM CARBONATE. 4.00
CUSTER SPAR......... 23.50
========
100.00
I did 2 tiles with the clear base and 4 with colorants in it. I have not
tested them to see how they handle thermal shock (boil/freeze routine)
because I seem to have other problems when I look at the tiles under a X10
magnifier. I suppose my first question would be, should I do it anyway or
wait until after I fix the _few_ pinholes and a fair amount of bubbles?
Tile A: +5% Tin, +4% Cobalt
-Blue; Shows pinholes on thicker parts; hard to tell elsewhere due to dark
color.
Tile B: +10% Superpax
-White; No apparent defects thick or thin. Best tile with D.
Tile C: +3% Lithium, +1% Cobalt, +0.5 Nickel
-Variegated transparent blue; Traps bubbles and shows pinholes the thicker
it gets.
Tile D: Clear - very thin coats
-Transparent; No apparent defects.
Tile E: +3% Lithium, +2% Copper Carbonate, +1% Spanish Red Iron
-Transparent green; few long crazing lines only on one side the first day;
now on the third, the lines have increased.
Tile F: Clear - twice as thick as tile D
-Transparent; shows few pinholes on the thick section.
Zinc and Rutile are of no concern. Next, I have ZERO control over the
length of the firing schedule, which seems to be the foremost fix. :( I
use the community college to fire my stuff.
What's left as a feasible fix for me would be to apply the glaze less
thickly; tile D seems to suggest that, but why then is my thick white just
fine? Lowering the fusion point seems to be a corollary fix, but superpax
contains no flux. And, tile C shows pinholes everywhere; isn't lithium a
flux at this range? It sounds backwards. Is there an explanation for this?
Could I get away with it if I just lowered the fusion point a bit (more
flux)? Or is the thin coat the obvious fix? It sounds rather difficult to
achieve the same thickness on every shape/pot and keep the glaze to the
perfect consistency, too.
Thank you for your time :)
$:0`0:$x,88,x$:0`0:$x,88,x$:0`0:$x,88,x$:0`0:$x,88,x$:0`
Fabienne
Yes, I have learned from my mistakes...
I can reproduce them exactly.
Ron Roy on mon 26 oct 98
------------------
Hi Fabienne,
Do the fit tests first - absolutely - then you can deal with any of those
problems as you are dealing with the others.
You are going to find the bubble thing exasperating no doubt - there are
always less on porcelain and always more on dark bodies. Keep the
application thin to minimize bubbles.
The thick white looks fine - cause you can't see the bubbles. They are only
an issue cause you can see em in the clear.
Lithium is an alkali and alkalies let bubbles grow,
There is a problem with lithium carb - well several actually - but lets do
the one that is raising the expansion to give the crazing. Take the
alkalies (K2O, Na2O and Li2O) as a group - if the lithium is less than 20=25
of that group - because lithium has a much lower expansion than both K and
Na then you can use it to replace some of the KNaO and lower the expansion
of a glaze. What you did is raise the level of L in that alkali group to
32.25=25 - Lithium - under that condition (over 20=25) actually raises the
expansion of your glaze - quite a bit - hence the crazing.
OK OK=21 - the other problems with lithium carb - it will deflocculate =
glazes
because it is somewhat soluble in the slop - and it had a toxic effect and
a little can do a lot. There is some evidence that some of that lithium
(the soluble part?) can effect the boundary layer between body and glaze
and give fit responses that are abnormal.
I don't recommend using lithium carb - if you need some lithium the
material of choice would be spodumene if you ask me.
RR
=3EHere is the recipe:
=3E
=3EFM091198 - =5E6 Clear Base for MCS
=3E=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D==
3D3D=3D=3D=3D=3D=3D=3D
=3E WOLLASTONITE........ 7.00
=3E EPK KAOLIN.......... 17.00
=3E FRIT 3134........... 27.00
=3E SILICA.............. 21.50
=3E STRONTIUM CARBONATE. 4.00
=3E CUSTER SPAR......... 23.50
=3E =3D=3D=3D=3D=3D=3D=3D=3D
=3E 100.00
=3E
=3EI did 2 tiles with the clear base and 4 with colorants in it. I have not
=3Etested them to see how they handle thermal shock (boil/freeze routine)
=3Ebecause I seem to have other problems when I look at the tiles under a =
X10
=3Emagnifier. I suppose my first question would be, should I do it anyway =
or
=3Ewait until after I fix the =5Ffew=5F pinholes and a fair amount of =
bubbles?
=3E
=3ETile A: +5=25 Tin, +4=25 Cobalt
=3E-Blue=3B Shows pinholes on thicker parts=3B hard to tell elsewhere due to=
dark
=3Ecolor.
=3E
=3ETile B: +10=25 Superpax
=3E-White=3B No apparent defects thick or thin. Best tile with D.
=3E
=3ETile C: +3=25 Lithium, +1=25 Cobalt, +0.5 Nickel
=3E-Variegated transparent blue=3B Traps bubbles and shows pinholes the =
thicker
=3Eit gets.
=3E
=3ETile D: Clear - very thin coats
=3E-Transparent=3B No apparent defects.
=3E
=3ETile E: +3=25 Lithium, +2=25 Copper Carbonate, +1=25 Spanish Red Iron
=3E-Transparent green=3B few long crazing lines only on one side the first =
day=3B
=3Enow on the third, the lines have increased.
=3E
=3ETile F: Clear - twice as thick as tile D
=3E-Transparent=3B shows few pinholes on the thick section.
=3E
=3EZinc and Rutile are of no concern. Next, I have ZERO control over the
=3Elength of the firing schedule, which seems to be the foremost fix. :( I
=3Euse the community college to fire my stuff.
=3E
=3EWhat's left as a feasible fix for me would be to apply the glaze less
=3Ethickly=3B tile D seems to suggest that, but why then is my thick white =
just
=3Efine? Lowering the fusion point seems to be a corollary fix, but =
superpax
=3Econtains no flux. And, tile C shows pinholes everywhere=3B isn't lithium=
a
=3Eflux at this range? It sounds backwards. Is there an explanation for =
this?
=3E
=3ECould I get away with it if I just lowered the fusion point a bit (more
=3Eflux)? Or is the thin coat the obvious fix? It sounds rather difficult =
to
=3Eachieve the same thickness on every shape/pot and keep the glaze to the
=3Eperfect consistency, too.
=3E
=3EThank you for your time :)
=3E
=3E=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=
=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=
=60
=3EFabienne
=3E Yes, I have learned from my mistakes...
=3E I can reproduce them exactly.
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
Fabienne Cassman on tue 27 oct 98
------------------
Hello,
Thank you for the replies :) According to what I received so far, the
first fix would be indeed to allow for a soaking period to let the bubbles
escape. The alternative would be to apply thin coats to minimize bubbles.
(I can't wait to have my own kiln so I don't have to tap dance.)
I see the usefulness of SrO as an auxiliary flux. However, it was pointed
out to me that even a small amount of carbonate creates bubbles=3B I gather
that it's the CO2 being released. Is it worth a try to reduce or remove
the strontium carbonate from the recipe? Can it solve or attenuate my
problem?
I finally came over a statement in Rhodes' book that I could raise the
fusion point, not lower it as I thought, to solve the bubble problem=3B
however, it makes absolutely no sense to me. Can someone try to explain it
to me?
I did the fit tests this week-end=3B all the tiles stayed the same except =
for
tile E which crazed a bit more. I'll check the Lithium issue out later =
on=3B
thank you for pointing out the solubility problem with lithium. I'll
create a new recipe with spodumene later on so I can play with that
variegated blue I like :)
Thank you again,
=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=
=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60
Fabienne
Yes, I have learned from my mistakes...
I can reproduce them exactly.
Ron Roy on thu 29 oct 98
------------------
Hi Fabienne,
Two answers: I have not noticed any lessing of bubbles when I have
eliminated the carbonates - thought i would but didn't.
Raising the alumina in a glaze will make it more viscous - which in turn
will have a negative effect on the formation and growth of bubbles. As I
said - the best strategy I can offer at his time is keep the application as
thin as you need for the effect you want and use a porcelain.
I will continue my experiments on clear bubbless glazes - just in a
thinking mode these days - and gotta make some pots - the customers are
getting impatient - bless em.
RR
=3EThank you for the replies :) According to what I received so far, the
=3Efirst fix would be indeed to allow for a soaking period to let the =
bubbles
=3Eescape. The alternative would be to apply thin coats to minimize =
bubbles.
=3E(I can't wait to have my own kiln so I don't have to tap dance.)
=3E
=3EI see the usefulness of SrO as an auxiliary flux. However, it was =
pointed
=3Eout to me that even a small amount of carbonate creates bubbles=3B I =
gather
=3Ethat it's the CO2 being released. Is it worth a try to reduce or remove
=3Ethe strontium carbonate from the recipe? Can it solve or attenuate my
=3Eproblem?
=3E
=3EI finally came over a statement in Rhodes' book that I could raise the
=3Efusion point, not lower it as I thought, to solve the bubble problem=3B
=3Ehowever, it makes absolutely no sense to me. Can someone try to explain =
it
=3Eto me?
=3E
=3EI did the fit tests this week-end=3B all the tiles stayed the same except=
for
=3Etile E which crazed a bit more. I'll check the Lithium issue out later =
on=3B
=3Ethank you for pointing out the solubility problem with lithium. I'll
=3Ecreate a new recipe with spodumene later on so I can play with that
=3Evariegated blue I like :)
=3E
=3EThank you again,
=3E=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=
=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=60=B0=BA=A4=F8,=B8=B8,=F8=A4=BA=B0=
=60
=3EFabienne
=3E Yes, I have learned from my mistakes...
=3E I can reproduce them exactly.
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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