Mary Graham on sat 1 apr 06
Does anyone know if I can substitute Nepheline Syenite for Kona F4 one to
one? Or is there something else I have to add? It's late, the weekend....
This is a cone 6 Majolica glaze with gerstley borate, KPK, whiting, flint
and zircopax....any suggestions?
Thank you!
Daniel Semler on sun 2 apr 06
Hi Mary,
In short, no. The composition of neph sye would leave you short on silica and
your flux balance would be altered a bit.
Had a quick look though. It seems that from an oxide point of view you could
fake kona f4 with the following neph sye based recipe :
neph sye : 75.90
whiting : 2.10
silica : 19.70
alumina hydrate : 2.30
This totals 100. Sub 100 grams of this for 100 grams of F4.
Its expansion is a little lower, not much. It will contain a trace of MgO -
don't think it will matter but ... Its LOI is up a hair but I wouldn't worry
about that. I don't know if it would feel different to paint on.
If you try it let us know how it goes.
Thanx
D
Steve Slatin on sun 2 apr 06
Mary --
In general outline, both Nepheline Syenite and
Kona F4 are low iron minerals that chemically are
feldspars (minerologically, Nepheline Syenite is
a different kind of rock, though I don't know
that this makes a difference in its use in
glazes).
Nepheline Syenite has more sodium, more alumina,
and less silica.
As to whether you can substitute one-for-one,
that depends on lots of things -- whether your
glaze is near the limits of good glass formation;
whether the glaze's color effect is highly
dependent on the alkali levels, and, most
importantly, whether your glaze calls for quite a
bit of F-4 or just a little.
When you're trying to substitute materials, it's
important to think of the concentration of those
materials in the glaze. The difference in silica
in this case, for example, is about 60% to about
67% -- if the glaze is 50% this item,
substitution will change the final glaze
composition by over 3%, which may well be
significant. If the glaze uses only 10% of this
material, the difference will be barely a half a
percent, and probably will not make a visible
difference.
Best wishes -- Steve Slatin
--- Mary Graham wrote:
> Does anyone know if I can substitute Nepheline
> Syenite for Kona F4 one to
> one? Or is there something else I have to add?
> It's late, the weekend....
> This is a cone 6 Majolica glaze with gerstley
> borate, KPK, whiting, flint
> and zircopax....any suggestions?
>
> Thank you!
Steve Slatin --
In the mornin’ cry of the rooster
The baby lay alone
And the old cow in the green grass
Shed white tears in the red hot sun
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Cynthia Bracker Sturm on sun 2 apr 06
Do you have any NC-4? That would substitute pretty well as they are
both soda spars. If not, I would look to a potash spar before neph
sye, but I'm not a glaze expert. Hopefully Ron will reply.
Cindy
On Apr 1, 2006, at 8:48 PM, Mary Graham wrote:
> Does anyone know if I can substitute Nepheline Syenite for Kona F4 one
> to
> one? Or is there something else I have to add? It's late, the
> weekend....
> This is a cone 6 Majolica glaze with gerstley borate, KPK, whiting,
> flint
> and zircopax....any suggestions?
>
> Thank you!
>
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Daniel Semler on mon 3 apr 06
Hi Mary,
Steve makes good points in his post. My outright "no" ought to be
reconsidered
in this light - it could work. That said, if you are using a bunch of
it or any
colourants are sensitive to the fluxes then maybe give the sub I sent a try.
That was my main thought concerning the fluxes when I made my comment on the
flux balance.
Thanx
D
Bryan Johnson on mon 3 apr 06
----- >> Does anyone know if I can substitute Nepheline Syenite for Kona
F4 one
>> to
>> one? Or is there something else I have to add? It's late, the
>> weekend....
>> This is a cone 6 Majolica glaze with gerstley borate, KPK, whiting,
>> flint
>> and zircopax....any suggestions?
>>
>> Thank you!
An approximate sub would be NS 82, wollastonite 3, and silica 15, to 100
parts of Kona.
Bryan Johnson
Ron Roy on tue 4 apr 06
I think Daniels would work - it's very close.
You could also use the following
Neph Sy - 77.0
wollas - 2.5
EPK 4.0
Silica 16.5
Total - 100.0
In theory - because wollas and EPK are already combined materials this
should melt a little better - I'd love to know if anyone tries both.
RR
RR
> In short, no. The composition of neph sye would leave you short on silica and
>your flux balance would be altered a bit.
>
> Had a quick look though. It seems that from an oxide point of view you could
>fake kona f4 with the following neph sye based recipe :
>
> neph sye : 75.90
> whiting : 2.10
> silica : 19.70
> alumina hydrate : 2.30
>
> This totals 100. Sub 100 grams of this for 100 grams of F4.
>
> Its expansion is a little lower, not much. It will contain a trace of MgO -
>don't think it will matter but ... Its LOI is up a hair but I wouldn't worry
>about that. I don't know if it would feel different to paint on.
>
> If you try it let us know how it goes.
>
>Thanx
>D
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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