Dave Finkelnburg on thu 7 dec 06
Ivor,
You advice to avoid Nepheline Syenite (NS) in
porcelain bodies is unfortunate. NS has proven to be
a suitable sodium source in porcelain recipes. At
least here in North America, where NS is readily
available, most commercial cone 5 porcelain is made
with NS as the flux source.
Yes, NS can cause plasticity problems over time as
sodium dissolves from it. There are ways to counter
this.
Any soda frit, by the way, will produce far more
soluble sodium than NS. A sodium frit placed into
deionized water, for example, will, within seconds,
produce a pH of almost 10 . :-(
Regards,
Dave Finkelnburg
--- Ivor and Olive Lewis
wrote:
> My second suggestion would be to avoid using
> Nepheline Syenite. There are two reasons. First,
> though only slightly soluble, this can lead to
> deflocculation problems and reduce plasticity.
> Second, Neph Sy. is a rock, not a single mineral.
> There is good reason to believe it has the
> properties of a Eutectic mixture which might account
> for the behaviour Alex Sola describes. This may
> depend on the proportions of three minerals,
> Nepheline, Soda Felspar and Leucite. If all three
> are present in a sample the Phase Diagram
> (K2O-Na2O-Al2O3-SiO2, Fig 786, p 265. Phase Diagrams
> for Ceramists. ACS) shows a melting point of 1020
> Deg C.
> Perhaps a better auxiliary body flux would be one of
> the higher melting point Frits. Choose one with
> minimal Soda in its composition and do a line blend
> with your felspar to get the mixture with the
> optimal fusion temperature.
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Ric Swenson on sat 9 dec 06
=20
=20
Howdee...y'all.
=20
=20
I have had good luck with replacement of some.... or all of Feldspar in a b=
ody with Neph. Sy. to lower the firing temperature. Maybe just my luck, bu=
t it seems to work.
=20
I must admit I have not yet tried it in China however....but I like cone 1=
3 fired wares a lot.
=20
Nepheline Syenite is just a source of Canadian "Feldspar'? from Mountain n=
ear Nepheline....Canada?.
=20
Which mavin knows the science behind this phenom?
=20
Worth a test at least.=20
=20
sorry....no matter what the 'science' says.=20
=20
The proof is in the pudding...you know?
=20
Ric
=20
> You(r) advise(c)e to avoid Nepheline Syenite (NS) in> porcelain bodies is=
unfortunate. NS has proven to be> a suitable sodium source in porcelain re=
cipes. At> least here in North America, where NS is readily> available, mos=
t commercial cone 5 porcelain is made> with NS as the flux source.> Yes, NS=
can cause plasticity problems over time as> sodium dissolves from it. Ther=
e are ways to counter> this.> Any soda frit, by the way, will produce far m=
ore> soluble sodium than NS. A sodium frit placed into> deionized water, fo=
r example, will, within seconds,> produce a pH of almost 10 . :-(> Regards,=
> Dave Finkelnburg> > --- Ivor and Olive Lewis > wro=
te:> > My second suggestion would be to avoid using> > Nepheline Syenite. T=
here are two reasons. First,> > though only slightly soluble, this can lead=
to> > deflocculation problems and reduce plasticity.> > Second, Neph Sy. i=
s a rock, not a single mineral.> > There is good reason to believe it has t=
he> > properties of a Eutectic mixture which might account> > for the behav=
iour Alex Sola describes. This may> > depend on the proportions of three mi=
nerals,> > Nepheline, Soda Felspar and Leucite. If all three> > are present=
in a sample the Phase Diagram> > (K2O-Na2O-Al2O3-SiO2, Fig 786, p 265. Pha=
se Diagrams> > for Ceramists. ACS) shows a melting point of 1020> > Deg C.>=
> Perhaps a better auxiliary body flux would be one of> > the higher melti=
ng point Frits. Choose one with> > minimal Soda in its composition and do a=
line blend> > with your felspar to get the mixture with the> > optimal fus=
ion temperature.> > > > ___________________________________________________=
_________________________________> Do you Yahoo!?> Everyone is raving about=
the all-new Yahoo! Mail beta.> http://new.mail.yahoo.com> > ______________=
________________________________________________________________> Send post=
ings to clayart@lsv.ceramics.org> > You may look at the archives for the li=
st or change your subscription> settings from http://www.ceramics.org/claya=
rt/> > Moderator of the list is Mel Jacobson who may be reached at melpots@=
pclink.com.
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Ivor and Olive Lewis on sun 10 dec 06
Dear Dave Finkelnburg,=20
Your admonition regarding my suggestion may be correct but I would like =
to know in what sense.
I believe I did give a response that urged caution, advocating a frit =
with a minimum soda content, and of adequate testing. It is difficult to =
obtain minerals that do not contain residual amounts of the element =
Sodium, a fact which can be demonstrated with a simple flame test.
My greater concern would be the fusion range of Nepheline Syenite, a =
rock with widely varying elemental composition that has the potential =
for Eutectic fusion far lower than the Cone value of the commercial Cone =
5 clay bodies you choose as examples.
On reflection my answer was incomplete. I neglected to suggest that an =
excellent way to solve the problem set by John Rodgers might be to use =
Cornish Stone or its USA equivalent. There is also great potential for =
using prefused felspar minerals, either alone or with minor additions of =
other oxides from the Alkali Earth series then milling the fused mixture =
to <200 # as a way of getting material that will assist vitrification at =
Cone 6 without the attendant drawbacks of either standard frits or Neph =
Sy.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Dave Finkelnburg on sun 10 dec 06
Ivor,
I don't want to make a big deal out of this, won't
say it again, but posts go to the archives to educate,
or mislead, so getting it right is important.
In your opinion Nepheline Syenite (NS) is a bad
clay body ingredient and you suggested use of a
commercial frit instead. I disagree on both counts.
Here in North America NS is used up to 1,200C to
flux commercial porcelain. I have personally used it
to flux a body at C5 and c10 with great success. The
firing range is wide, the body as suitable as one
fluxed with other materials.
I agree, soluble sodium from NS tends to
deflocculate a body over time. This tendency needs to
be countered. IF one can formulate a recipe with a
less soluble material that is certainly better.
However, commercial frits are far more expensive and
more soluble than NS. They can be ground as finely,
but usually are not.
My practical experience has been Nepheline Syenite
is a useful clay body material.
Regards,
Dave Finkelnburg
--- Ivor and Olive Lewis
wrote:
> Dear Dave Finkelnburg,
> Your admonition regarding my suggestion may be
> correct but I would like to know in what sense.
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Michael Wendt on sun 10 dec 06
To add to Dave's comments,
I have used Nepheline Syenite
a half the flux content in my clay
bodies for over 30 years.
I do so because I fast fire:
In by 10:00... over by 5:00 the
same day to cone 10.
To counteract deflocculation,
I use an additive called DR-10
which is available locally as a
very powerful flocculcant for
$15.00/gallon. A small amount
is added tot he water when we mix
and it flocculates the clay despite
the Nepheline Syenite.
Unlike Epsom Salts which I had tried
before, it contains no sulfur so it
doesn't outgas and cause blistering with
some glazes or precipitate on rims and
cause overfluxing there.
I heartily recommend the use of
Neph Sye if you want to lower the
melting point of a clay body.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Edouard Bastarache Inc. on sun 10 dec 06
David and Ivor,
European Nepheline/Syenite is quite more stable
than the stuff mined here.
Later,
Edouard Bastarache
Le Français Volant
The Flying Frenchman
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.pshcanada.com/Toxicology.htm
http://www.flickr.com/photos/30058682@N00/
http://www.ceramique.com/cerambooks/rayons/technologie.php
----- Original Message -----
From: "Dave Finkelnburg"
To:
Sent: Sunday, December 10, 2006 11:29 AM
Subject: Re: Mel's 4X25 Porcelain Body--Nepheline
Syenite
> Ivor,
> I don't want to make a big deal out of this,
> won't
> say it again, but posts go to the archives to
> educate,
> or mislead, so getting it right is important.
> In your opinion Nepheline Syenite (NS) is a
> bad
> clay body ingredient and you suggested use of a
> commercial frit instead. I disagree on both
> counts.
> Here in North America NS is used up to 1,200C
> to
> flux commercial porcelain. I have personally
> used it
> to flux a body at C5 and c10 with great success.
> The
> firing range is wide, the body as suitable as
> one
> fluxed with other materials.
> I agree, soluble sodium from NS tends to
> deflocculate a body over time. This tendency
> needs to
> be countered. IF one can formulate a recipe
> with a
> less soluble material that is certainly better.
> However, commercial frits are far more expensive
> and
> more soluble than NS. They can be ground as
> finely,
> but usually are not.
> My practical experience has been Nepheline
> Syenite
> is a useful clay body material.
> Regards,
> Dave Finkelnburg
>
>
> --- Ivor and Olive Lewis
> wrote:
>> Dear Dave Finkelnburg,
>> Your admonition regarding my suggestion may be
>> correct but I would like to know in what sense.
>
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam? Yahoo! Mail has the best spam
> protection around
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>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or
> change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots@pclink.com.
>
Ivor and Olive Lewis on mon 11 dec 06
Dear Ric Swenson,
You ask <> regarding =
the way in which Neph Sy will decrease the maturity temperature of a =
glaze.
Nep Sy, which is a rock and an intimate mineral association of K and Na =
spars, appears to incorporate a Natural Eutectic with a fusion point on =
heating of 1020 deg Celsius. Which seems as good a reason as "Luck" for =
your success.
Someone with access to the real archives might like to confirm or refute =
that proposition.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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