Assumption Abbey on wed 28 jul 99
Dear Readers,
I know I have come accross this in reading somewhere.... I am mixing a
copper glaze and it calls for a fieldspar. I did the test tile by using
(KONA F-4) and like the results.
Would custer Fieldspar produce good results also? I guess my question
is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
using Copper Glaze #3 by James Chappel.
Any hints and helps would be welcomed. Very pretty on porcelain
Llewellyn Kouba
ABBEY POTTERY
http://www.assumptionabbey.com/Pottery.html
Marcia Selsor on fri 30 jul 99
Hi, Lewellyn,
I would like F-4 because it is a soda ash feldspar wjere Custer (and I
know you are next door to that source) is a potash feldspar.
Wait to hear from Ron Roy, glaze guru.
Best wishes to you and I hope you are surviving the heat out there in
your beautiful prairie land.
Marcia
Assumption Abbey wrote:
>
> ----------------------------Original message----------------------------
>
> Dear Readers,
>
> I know I have come accross this in reading somewhere.... I am mixing a
> copper glaze and it calls for a fieldspar. I did the test tile by using
> (KONA F-4) and like the results.
>
> Would custer Fieldspar produce good results also? I guess my question
> is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
> using Copper Glaze #3 by James Chappel.
>
> Any hints and helps would be welcomed. Very pretty on porcelain
>
> Llewellyn Kouba
> ABBEY POTTERY
> http://www.assumptionabbey.com/Pottery.html
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
Mike Bailey on sun 1 aug 99
In message , Assumption Abbey writes
Dear Llewellyn,
In my experience there's not a lot of difference - but, if pushed I'd
say the soda gives the slightly brighter results,
Cheers,
Mike Bailey.
>----------------------------Original message----------------------------
>
>Dear Readers,
>
> I know I have come accross this in reading somewhere.... I am mixing a
>copper glaze and it calls for a fieldspar. I did the test tile by using
>(KONA F-4) and like the results.
>
> Would custer Fieldspar produce good results also? I guess my question
>is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
>using Copper Glaze #3 by James Chappel.
>
> Any hints and helps would be welcomed. Very pretty on porcelain
>
>
>Llewellyn Kouba
>ABBEY POTTERY
>http://www.assumptionabbey.com/Pottery.html
>
--
Mike Bailey
Assumption Abbey on sun 1 aug 99
At 10:29 7/30/99 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi, Lewellyn,
>I would like F-4 because it is a soda ash feldspar wjere Custer (and I
>know you are next door to that source) is a potash feldspar.
>Wait to hear from Ron Roy, glaze guru.
>Best wishes to you and I hope you are surviving the heat out there in
>your beautiful prairie land.
>Marcia
>---------------
Hi Marcia,
Great to hear from you. I have gotten a few responses to my question
and I know I had this in writting somewhere and have added the info
directly to my files and after a while you get to know this stuff better
and don't have to rely so much on the notes too.
I am very busy with two very full bisque loads sitting and waiting to
be glazed. I also sit in the height of the tourist season with the 'empty
shelves' syndrome. Oh, well better that than things not moving. And of
course the studio is really a hot one. We have been in the 100 for a
couple days and sleeping at night isn't much better with only fans and no
air conditioning of any sort.
I am excited about the next glaze firings and am working on test tiles
today.
I find myself particularily this time of year 'missing Montana' as I have
gone out your way for a couple years now in a row but don't have any
immediate plans for any kind of vacation. In August 15-20 I will be taking
a workshop here with the 'Prairie Rose Rug Hooking School'....should be
great fun huh. I confess I love the arts, crafts of all kinds, anything
creative and I confess I am a 'closet hooker' :)
Best regards and have a great summer of firing the kilns
>Assumption Abbey wrote:
>>
>> ----------------------------Original message----------------------------
>>
>> Dear Readers,
>>
>> I know I have come accross this in reading somewhere.... I am mixing a
>> copper glaze and it calls for a fieldspar. I did the test tile by using
>> (KONA F-4) and like the results.
>>
>> Would custer Fieldspar produce good results also? I guess my question
>> is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
>> using Copper Glaze #3 by James Chappel.
>>
>> Any hints and helps would be welcomed. Very pretty on porcelain
>>
>> Llewellyn Kouba
>> ABBEY POTTERY
>> http://www.assumptionabbey.com/Pottery.html
>
>--
>Marcia Selsor
>selsor@imt.net
>http://www.imt.net/~mjbmls
>http://www.imt.net/~mjbmls/spain99.html
>http://www.silverhawk.com/ex99/selsor/welcome.html
>
Llewellyn Kouba
ABBEY POTTERY
http://www.assumptionabbey.com/Pottery.html
Ron Roy on mon 2 aug 99
Hi Liewellyn,
The reason we use so much feldspar in our glazes and bodies - it is the
cheapest source of insoluble alkalies - sodium and potassium. In this case
they are the main oxides that promote the blue from copper. Lithium, barium
and calcium oxide are also helpful. The oxides that work against that
particular colour are lead, boron, magnesium amd alumina Oxide.
So which would be better F4 or Custer. Well F4 does have more Sodium than
potassium - but that is not the main thing here. Potassium is going to give
the same colour. There is another factor involved - alkaline glazes are
very hard to stop crazing because the expansion rate of both sodium and
potassium is the highest of all the oxides we use - and potassium's is a
bit lower than sodium's.
Starting at cone 6 sodium starts to become volitile - which may be a factor
in some situations.
The total alkalies (KNaO) found typically in F4 spar = 11.72 (4.81 K2O,
6.91 Na2) - the total alkalies in Custer = 13.14 (K2O = 10.11, Na2O =
3.03.)
So you see - from an economic point of view the Custer wins hands down.
The F4 also has more Alumina - so again it is clearly not the best from
that stand point.
In the end we still have to do a test and compare - and to do it right we
should not only simply substitute the Custer for the F4 but should also
correct for the Custer (by calculation) to see if there will be a
difference in clour when there is more K2O than Na2O.
To do that I need the original glaze recipe - it will take me about 10 min.
RR
>> ----------------------------Original message----------------------------
>>
>> Dear Readers,
>>
>> I know I have come accross this in reading somewhere.... I am mixing a
>> copper glaze and it calls for a fieldspar. I did the test tile by using
>> (KONA F-4) and like the results.
>>
>> Would custer Fieldspar produce good results also? I guess my question
>> is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
>> using Copper Glaze #3 by James Chappel.
>>
>> Any hints and helps would be welcomed. Very pretty on porcelain
>>
>> Llewellyn Kouba
>> ABBEY POTTERY
>> http://www.assumptionabbey.com/Pottery.html
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Gavin Stairs on wed 4 aug 99
At 09:45 AM 02/08/99 , Ron Roy wrote:
...
>The reason we use so much feldspar in our glazes and bodies - it is the
>cheapest source of insoluble alkalies - sodium and potassium.
...
Feldspar is also the primary source of clay in the first place. Kaolin
containing clay comes mostly from igneous rocks weathered so that the
fluxing stuff is removed, and the hydrated remains are clay. I see a
wonderful symmetry in this. Clay is used for the form, and the mother of
clay is used for the glaze. I remember first reading about Hamada's
glazes, and thinking about this. Seemed rather poetic. Then I found out
that he was a trained glaze chemist. Still, what he did was mostly to
modify the traditional materials to suit his own purposes, so it wasn't far
away from the poetic notion.
Gavin
pam pulley on fri 6 aug 99
In our studio we had a nice blue chun glazed mixed with custer feldspar.
Someone new to glaze mixing mixed up the next bucket and it turned out to be
a purple chun. What a suprize and a beautiful glaze. The second bucket was
mixed with Soda Feldspar. Now we mix and use both regularly.
>From: Mike Bailey
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.UKY.EDU
>Subject: Re: Which Feldspar to develope the best blue?
>Date: Sun, 1 Aug 1999 11:09:53 EDT
>
>----------------------------Original message----------------------------
>In message , Assumption Abbey writes
>Dear Llewellyn,
>
>In my experience there's not a lot of difference - but, if pushed I'd
>say the soda gives the slightly brighter results,
>
>Cheers,
>
>Mike Bailey.
>
>
> >----------------------------Original message----------------------------
> >
> >Dear Readers,
> >
> > I know I have come accross this in reading somewhere.... I am mixing
>a
> >copper glaze and it calls for a fieldspar. I did the test tile by using
> >(KONA F-4) and like the results.
> >
> > Would custer Fieldspar produce good results also? I guess my
>question
> >is which Fieldspar should I use in a copper glaze? Kona or Custer? I am
> >using Copper Glaze #3 by James Chappel.
> >
> > Any hints and helps would be welcomed. Very pretty on porcelain
> >
> >
> >Llewellyn Kouba
> >ABBEY POTTERY
> >http://www.assumptionabbey.com/Pottery.html
> >
>
>--
>Mike Bailey
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