Lili Krakowski on wed 6 apr 11
I feel for you Eileen, because crawling is one of those real =3D
heartaches...more maybes than answers.
My instant suggestion is use another clear...Heaven knows there are many =
=3D
around. =3D20
But here goes:
Worthington Clear: =3D20
55 Gerstley Borate
30 Kaolin--EPK
15 Flint
.117 Na2O
.006 K2O
.004 MgO
.874 CaO
.666 Al2O3
.914 B2O3
2.967 SiO2
.005 TiO2
.
61.4 Exp
Worthington Clear Revise
50 Gerstley Borate =3D20
16 Kaolin--EPK
17 Kaolin--Calcined
17 Flint
100 Total
.119 Na2O
.005 K2O
.01 MgO
.865 CaO
1.000 Total
.811 Al2O3
.895 B2O3
3.485 SiO2
.
59.6 Exp
Calculations by GlazeMasterT
Both these glazes are below what "Mastering the Art" tells us--that a =3D
glaze should have an expansion rate above 65. (Read up as to why) And I =
=3D
think the Alumina high, But the glaze worked for a time...and that is =3D
where I am going to look.
As Michael Bailey also notes, many of us call Gerstley Borate "Ghastly =3D
Borate" because is it such a pain. It makes the most ficklle lover in =3D
your whole
entire life seem like a trustworthy, reliable gem! (And its cousin, =3D
Colemanite, was no better!)
It is a mined material and there are great variations...so each batch =3D
that comes new into the studio needs to be tested. It contains variable =
=3D
amounts
of soluble materials, to which we will return.
What I think is happening is that you got a new batch of GB. That there =
=3D
are more solubles in there than before. That, and you know this, but =3D
some
readers might not, the water carries the solubles into the =3D
body...depriving the rest of the glaze of them. Also depriving the rest =
=3D
of the bucket.=3D20
So the problem gets worse the longer that bucket of glaze is in use. =3D
And if at some point the glaze has settled and was too thin, and someone =
=3D
pours off
the "excess" water.....It is to shudder!
It would be the kind of fun glazenuts love to test this GB for a while, =3D
in other glazes that use it. No time for that now.
My strong recommend is that you kick the bum out, and use another glaze. =
=3D
As you do not tell us what cone you are firing to, here are two glazes. =
=3D
As you see
siblings.
Karen's 04 clear
55.6 Frit--Ferro 3134
23.8 Kaolin--EPK
20.6 Flint
100 Total
.303 Na2O
.003 K2O
.002 MgO
.691 CaO
.287 Al2O3
.604 B2O3
.003 Fe2O3
3.069 SiO2
10.7 Ratio
72.6 Exp
And for c.6 my standard all purpose BB Clear
BB clear
69.1 Frit--Ferro 3124
7.2 Ball Clay--Old Mine #4
21.6 Flint
2.2 Bentonite
.269 Na2O
.023 K2O
.008 MgO
.7 CaO
.343 Al2O3
.512 B2O3
.004 Fe2O3
3.995 SiO2
67.1 Exp
Calculations by GlazeMasterT
And, as I use this a lot, and am bone [ash] lazy:
4.5 cups of 3124, 1 c. kaolin, 1 cup silica, 1/4 c. Bentonite. You do =3D
not need to use standard measuring cups. I scoop the material from bin, =
=3D
but do not pack it down. And (test!) I think any ball clay should work.
And a last, grim thought. Your clay body may have changed. Please not =3D
to tell me that it is Mitzi's Magic Body and you have used that brand =3D
for years.
It still may have changed. Again, once more, in pitiful and humble =3D
tones, I whine: keep several bodies in your firing range in the studio, =3D
so you
can compare glaze results and figure out what is the glaze's fault, what =
=3D
is the body's.
I wish you the best. You'se IS the best...a caring teacher.
Lili Krakowski
Be of good courage
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