ranmcc@MSN.COM on wed 23 sep 09
I have been firing to a hard Cone 6 (large cone is almost flat) which is
probably a Cone 7 in the sitter. One of my glazes which is a Cone 5 glaze
was having some pinholes so I was going to try to adjust the glaze by addin=
g
some ball clay. The glaze is a variation of Chappell's Floating Blue. The
main change that I did was to add 6% more ball clay. Wanted some feedback
as to whether the below glaze will fire to Cone 7 ok. I am doing a test
right now, but will not know until tomorrow late. Would another change be
better?
Recipe Name: Blue Lagoon
Cone: 6 Color: BLUE
Firing: Oxidation Surface: Glossy
Amount Ingredient
44.2 Nepheline Syenite
25.2 Gerstley Borate--1999
18.9 Silica
11.7 Ball Clay Number 1
100 Total
Additives
4 Rutile
1.5 Cobalt Carbonate
Unity Oxide
.416 Na2O
.114 K2O
.009 MgO
.461 CaO
1.000 Total
.79 Al2O3
.473 B2O3
.005 Fe2O3
4.964 SiO2
.009 TiO2
6.3 Ratio
72.2 Exp
Randy
Ron Roy on thu 24 sep 09
Hi Randy,
If you look at the amount of alumina in this glaze you will see it is way
over the usual amount for even a cone 10 glaze - I am assuming the pin hole=
s
will get worse with the added ball clay.
Keep in mind - one of the cures for pin holes is lowering alumina or raisin=
g
the oxides that promote running - like KNaO.
Making sure all organics are out during a bisque firing is another cure and
so is soaking.
If a clay is being over fired and gasses are starting to escape could be
another cause - are you using a cone 6 clay? Do you think it's over
vitrified?
Let me know if you need more on this - RR
On Wed, Sep 23, 2009 at 3:41 PM, wrote:
> I have been firing to a hard Cone 6 (large cone is almost flat) which is
> probably a Cone 7 in the sitter. One of my glazes which is a Cone 5 glaz=
e
> was having some pinholes so I was going to try to adjust the glaze by
> adding
> some ball clay. The glaze is a variation of Chappell's Floating Blue. T=
he
> main change that I did was to add 6% more ball clay. Wanted some feedbac=
k
> as to whether the below glaze will fire to Cone 7 ok. I am doing a test
> right now, but will not know until tomorrow late. Would another change b=
e
> better?
>
>
> Recipe Name: Blue Lagoon
>
> Cone: 6 Color: BLUE
> Firing: Oxidation Surface: Glossy
>
> Amount Ingredient
> 44.2 Nepheline Syenite
> 25.2 Gerstley Borate--1999
> 18.9 Silica
> 11.7 Ball Clay Number 1
>
> 100 Total
>
> Additives
> 4 Rutile
> 1.5 Cobalt Carbonate
>
> Unity Oxide
> .416 Na2O
> .114 K2O
> .009 MgO
> .461 CaO
> 1.000 Total
>
> .79 Al2O3
> .473 B2O3
> .005 Fe2O3
>
> 4.964 SiO2
> .009 TiO2
>
> 6.3 Ratio
> 72.2 Exp
>
> Randy
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
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