mudduck on fri 3 dec 10
My supplier is out of custer feldspar and will not have any for a week. =3D
I need to mix glaze this weekend.=3D20
I've got a bag of G-200, don't really remember why I have it but it's =3D
here.=3D20
As best as I can tell G-200 will sub just fine for custer and not show =3D
any difference in the glaze. Is this true?? If so I'll get to mixing.
Thanks!!!!
Gene
mudduck@mudduckpottery.net
www.mudduckpottery.net
David Hendley on fri 3 dec 10
G-200 is known to be a good substitute for Custer and Gene will
probably be fine to proceed with the substitution...
But, you knew there was a but,
I recently fired side-by-side test buttons, and was shocked at how
different these 2 materials fired at cone 10.
G-200 was melted into a concave puddle and was milky white.
Custer was somewhat melted, but still in that convex shape of
a material not completely melted. Custer was also very dirty
looking - smoky gray rather than white.
Since I ran this test, I have been switching over to using G-200
as my potash feldspar, since I usually want more melting power.
For delicate-colored glazes, such as pale transparents or celadon,
I would definitely use G-200 because of it's cleaner clear
look.
David Hendley
david@farmpots.com
http://www.farmpots.com
http://www.thewahooligans.com
----- Original Message -----
My supplier is out of custer feldspar and will not have any for a week. I
need to mix glaze this weekend.
I've got a bag of G-200, don't really remember why I have it but it's here.
As best as I can tell G-200 will sub just fine for custer and not show any
difference in the glaze. Is this true?? If so I'll get to mixing.
Thanks!!!!
Gene
mudduck@mudduckpottery.net
www.mudduckpottery.net
jonathan byler on fri 3 dec 10
should be pretty close, but is not exact. also depends on whether you
have the old unblended G-200, the not so old, but blended g-200, or
the new g-200 HP.
On Dec 3, 2010, at 4:41 PM, mudduck wrote:
> My supplier is out of custer feldspar and will not have any for a
> week. I need to mix glaze this weekend.
>
> I've got a bag of G-200, don't really remember why I have it but
> it's here.
>
> As best as I can tell G-200 will sub just fine for custer and not
> show any difference in the glaze. Is this true?? If so I'll get to
> mixing.
>
> Thanks!!!!
> Gene
> mudduck@mudduckpottery.net
> www.mudduckpottery.net
James Freeman on fri 3 dec 10
On Fri, Dec 3, 2010 at 5:41 PM, mudduck wrote:
> My supplier is out of custer feldspar and will not have any for a week. I=
=3D
need to mix glaze this weekend.
>
> I've got a bag of G-200, don't really remember why I have it but it's her=
=3D
e.
>
> As best as I can tell G-200 will sub just fine for custer and not show an=
=3D
y difference in the glaze. Is this true?? If so I'll get to mixing.
Gene...
The short answer is that there is almost no difference between Custer
feldspar and the old G-200. The old G200 has a tiny bit less silica
and a tiny bit more alumina, plus a trace more
calcium and potassium than Custer. The new G-200-HP is a different
animal. I posted the following to the list some years ago. I dug it
out of the archives, and thought I would re-post it here:
***************************************************************************=
=3D
************************************************************
Last year a friend asked me for help solving a glaze problem involving
G200 spar. I did some research for him. I dug through my records,
located the email, and thought I would share a slightly redacted
version. If anyone wants the supporting documentation mentioned in
the email, just let me know off list and I will forward the pdf files.
If a lot of folks want the documents, I will upload the files to the
clayart download page on my website:
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D
After you told me about your professor's problem with the changes in G200
feldspar, I did some research on the new G200-HP (I don't even use
the stuff, but I got curious). You might want to forward this email to
him, as it solves his dilemma.
In a nutshell, the original deposit of G200 spar ran out many years
ago. They opened a new deposit, but it had a much higher potash
content and a much lower sodium content. To compensate for this, they
blended 70% of the new deposit with 30% soda spar to get a similar
analysis to the old, and continued to sell this blend as G200 without
telling their customers about the change. Now, with fuel prices so
high, the new owners have stopped blending in the soda spar, and are
selling the new deposit straight, calling it G200-HP. I have attached
the supporting documentation, including chemical analyses of the old
G200 and the new G200-HP.
Your professor can simply bulk blend 70% G200-HP with 30% soda spar and
call it "G200". Alternatively, he can recalculate his recipes to use
70% of the original amount of G200 plus 30% of that amount in soda
spar. For example, if the batch called for 50% G200, he would now use
35% G200-HP (.50 x .70) plus 15% soda spar (.50 x .30). Perhaps
simplest of all, he could always try subbing Custer spar for the G200,
as the differences between the two are almost insignificant. G200 had
a tiny bit less silica and a tiny bit more alumina, plus a trace more
calcium and potassium than Custer, so unless a glaze was right on the
edge crazing or viscosity-wise at a given cone, the differences should
be imperceptible. I have also attached the most recent analysis of
Custer feldspar to support these statements. Of course, after you
complete Ron's glaze calc course, you will be in a position to easily
recalculate the entire glaze formula to use Custer spar and still
match precisely the analysis of the original glaze that used G200.
Ingredient substitution is the main power of glaze calculation. If
you don't want to wait for Ron's class, I can show you how to do this.
The change to G200 can actually be looked upon as a benefit rather
than a problem. Since the new G200-HP has 15% K (potassium) versus
the 10% of Custer and the old G200, we can now experiment with a whole
new field of very high potassium glazes without having to resort to
soluble sources of K such as pearl ash, and without introducing too
much silica and alumina which would come with simply adding more
feldspar. Have fun! As that extremely annoying saying goes, "It's
all good".
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=
=3D3D=3D3D
All the best.
...James
James Freeman
"...outsider artists, caught in the bog of their own consciousness,
too preciously idiosyncratic to be taken seriously."
"All I say is by way of discourse, and nothing by way of advice.=3DA0 I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
Ron Roy on fri 3 dec 10
Hi Gene,
Depends on what kind of glaze and how much spar in the glaze - I can
take a look at your glazes and tell you better then - trouble is I'm
away till Sunday.
It probably is OK - maybe only small changes
RR
Quoting mudduck :
> My supplier is out of custer feldspar and will not have any for a
> week. I need to mix glaze this weekend.
>
> I've got a bag of G-200, don't really remember why I have it but it's her=
e.
>
> As best as I can tell G-200 will sub just fine for custer and not
> show any difference in the glaze. Is this true?? If so I'll get to
> mixing.
>
> Thanks!!!!
> Gene
> mudduck@mudduckpottery.net
> www.mudduckpottery.net
>
David Beumee on sat 4 dec 10
I've fired the blended G-200 next to Custer, side by side fusion buttons at
cone 10 in reduction. G-200 has a clearer, more translucent melt and settle=
s
down more than Custer, which held its inverted crucible form. Custer is a
more opaque melt from the bags I tested, and is very clean burning, as is
the blended G-200. I have used Custer and G-200 in porcelain clay bodies,
and my research has shown that the difference in the side by side melts
doesn't give a clear picture of the difference in melting power. A little
G-200 goes a long way in comparison to Custer, but it's a moot point since
the blended G-200 is no longer available. I haven't tested the G-200 High
Potassium (HP) as yet, and have begun using a proportion of soda spar in my
bodies along with Custer to keep the non plastic ingredients to a minimum
while giving me the fluxing power I require to keep my porcelains at 0%
absorption at cone 10.
David Beumee
Porcelain by David Beumee
Lafayette, CO
On Fri, Dec 3, 2010 at 6:19 PM, Ron Roy wrote:
> Hi Gene,
>
> Depends on what kind of glaze and how much spar in the glaze - I can
> take a look at your glazes and tell you better then - trouble is I'm
> away till Sunday.
>
> It probably is OK - maybe only small changes
>
> RR
>
>
>
> Quoting mudduck :
>
> My supplier is out of custer feldspar and will not have any for a
>> week. I need to mix glaze this weekend.
>>
>> I've got a bag of G-200, don't really remember why I have it but it's
>> here.
>>
>> As best as I can tell G-200 will sub just fine for custer and not
>> show any difference in the glaze. Is this true?? If so I'll get to
>> mixing.
>>
>> Thanks!!!!
>> Gene
>> mudduck@mudduckpottery.net
>> www.mudduckpottery.net
>>
>>
Hank Murrow on sun 5 dec 10
On Dec 4, 2010, at 7:55 PM, David Beumee wrote:
> I haven't tested the G-200 High
> Potassium (HP) as yet,=3D20
I have done side by side fusion buttons of G200 and G200HP to find =3D
little difference to speak of in their melt quality. Where the =3D
difference lies is in the color response of certain oxides, as one =3D
should expect from the higher Potassium content.
Cheers, Hank=3D
Robert Santerre on fri 10 dec 10
Hank, can you give us an idea (examples) of some of the differences in
color response you've noticed?
Thanks, Bob
//////////////////////////////////////////////////////////////////////
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of Hank Murrow
Sent: Sunday, December 05, 2010 9:51 AM
To: Clayart@LSV.CERAMICS.ORG
Subject: Re: custer or g-200
On Dec 4, 2010, at 7:55 PM, David Beumee wrote:
> I haven't tested the G-200 High
> Potassium (HP) as yet,
I have done side by side fusion buttons of G200 and G200HP to find little
difference to speak of in their melt quality. Where the difference lies is
in the color response of certain oxides, as one should expect from the
higher Potassium content.
Cheers, Hank
Hank Murrow on fri 10 dec 10
On Dec 10, 2010, at 7:56 AM, Robert Santerre wrote:
> Hank, can you give us an idea (examples) of some of the differences =3D
in
> color response you've noticed?
Bob;
Celadons better reveal their bluish color as long as there is no titania =
=3D
in body or glaze. Certain copper colors change with the absence of =3D
sodium. Near-saturated Iron blues are better, especially above cone 10. =3D
I have embraced G200 HP as a valued addition to my feldspar collection.
Cheers, Hank=3D
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