Jean Eiers-Page on mon 10 oct 11
Hi,
Can I substitute Custer feldspar for Kona feldspar in the following recipe?
Thanks for your help.
Jean
Ron Roy Black, ^6 ox. one of several rev.
CM Oct. 2003
Recipe Name: Ron Roy Black, Rev.
Cone: 6 Color:
Firing: Oxidation Surface: Glossy
Amount Ingredient
3 Talc
6 Whiting
21 Feldspar--Kona F4
17 Kaolin--EPK
27 Silica
74 Total
Additives
1 Cobalt Carbonate
9 Iron Oxide--Red
Steve Slatin on mon 10 oct 11
This is a tougher question than it seems -- sorry for the length of the res=
=3D
ponse.=3D0A=3DA0=3D0ACuster is a high potassium feldspar -- 10.28% potassiu=
m oxid=3D
e and only 2.91% sodium oxide.=3D0AIt's got about 69% silica and a little m=
or=3D
e than 17% alumina.=3D0A=3DA0=3D0AKona is a soda feldspar.=3DA0 It's got on=
ly 4.81%=3D
potassium oxide, and 6.40% sodium. (Silica=3D0A67% or so, and alumina 19.4=
%.=3D
)=3D0A=3D0ASo they are=3DA0not 1 to 1 substitutable, and they will have bot=
h some=3D
what different melting=3D0Acharacteristics and coefficients of expansion, e=
tc=3D
.=3D0A=3D0ABut here's the interesting thing -- the feldspar is only about a=
fif=3D
th of the total weight of the =3D0Aglaze you're mixing.=3DA0 So the fact th=
at y=3D
ou're doubling your potassium and halving your sodium=3D0Ain the single ing=
re=3D
dient becomes quite a bit less of a difference in the final totals.=3DA0 Al=
so=3D
, they=3D0Ado, to a certain extent, cancel each other out (each is an alkal=
i,=3D
etc.) and while the recipe with=3D0ACuster will have more silica and less =
al=3D
umina (and thus be more likely to be glossy and runny)=3D0Ait has slightly =
le=3D
ss flux (and, importantly, less alkali) so it will more likely be a bit les=
=3D
s well =3D0Avitrified and runny).=3D0A=3D0ASo it might work, but might not,=
depen=3D
ding -- which is sort of the answer to nearly every=3D0Aquestion in the gla=
ze=3D
world.=3DA0 The only way to know for sure is to make a test batch, put it =
on=3D
=3D0Ayour test tile made of your clay, and see what happens.=3D0A=3D0AOne m=
ore th=3D
ing -- if you have Minspar, it IS a direct one-for-one substitute for Kona.=
=3D
=3D0A=3D0A=3D0ASteve Slatin -- =3D0A=3D0A=3D0AN48.0886450=3D0AW123.1420482=
=3D0A=3D0A=3D0A______=3D
__________________________=3D0A=3D0AHi,=3D0A=3D0ACan I substitute Custer fe=
ldspar f=3D
or Kona feldspar in the following recipe?=3D0A=3D0AThanks for your help.=3D=
0A=3D0AJ=3D
ean=3D0ARon Roy Black, ^6 ox. one of several rev.=3D0A=3D0ACM Oct. 2003=3D0=
A
William & Susan Schran User on mon 10 oct 11
On 10/10/11 11:49 AM, "Jean Eiers-Page" wrote:
> Can I substitute Custer feldspar for Kona feldspar in the following recip=
=3D
e?
> Thanks for your help.
> Jean
> Ron Roy Black, ^6 ox. one of several rev.
> CM Oct. 2003
> Recipe Name: Ron Roy Black, Rev.
> Cone: 6 Color:
> Firing: Oxidation Surface: Glossy
> Amount Ingredient
> 3 Talc
> 6 Whiting
> 21 Feldspar--Kona F4
> 17 Kaolin--EPK
> 27 Silica
> 74 Total
> Additives
> 1 Cobalt Carbonate
> 9 Iron Oxide--Red
Sure, you can substitute one for the other, it just won't be the same glaze=
=3D
.
Custer is a potash spar and Kona F4 is a soda spar.
I substituted Minspar directly for the Kona F4 and it worked for me.
Another thing - On my web site I have the recipe for a variation on Ron
Roy's Black:
Custer Potash Feldspar =3DAD 22 =3DAD 1100
Whiting =3DAD 2 =3DAD 200
Talc =3DAD 5 =3DAD 250
Ferro Frit 3134 =3DAD 26 =3DAD 1300
EPK =3DAD 17 =3DAD 850
Silica (325m) =3DAD 26 =3DAD 1300
Bentonite =3DAD 2 =3DAD 100
Red Iron Oxide =3DAD 9 =3DAD 450
Cobalt Carbonate =3DAD 1 =3DAD 50
Since your base batch amount only totals 74, I wonder if you are missing a
component - the frit that supplies the boron flux.
Bill
--=3D20
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Ron Roy on tue 11 oct 11
Hi Jean,
That is not a cone 6 glaze - you have left out the frit.
I think the glaze will be fine - just don't mix up too much to start
with in case you fine it too shiny. I can make adjustments for you if
you need them.
That glaze will be blacker with 2 cobalt carb by the way.
Ron Roy
Quoting Jean Eiers-Page :
> Hi,
>
> Can I substitute Custer feldspar for Kona feldspar in the following recip=
e?
>
> Thanks for your help.
>
> Jean
> Ron Roy Black, ^6 ox. one of several rev.
>
> CM Oct. 2003
> Recipe Name: Ron Roy Black, Rev.
>
> Cone: 6 Color:
> Firing: Oxidation Surface: Glossy
>
> Amount Ingredient
> 3 Talc
> 6 Whiting
> 21 Feldspar--Kona F4
> 17 Kaolin--EPK
> 27 Silica
>
> 74 Total
>
> Additives
> 1 Cobalt Carbonate
> 9 Iron Oxide--Red
>
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