Mudfingers@aol.com on wed 17 apr 96
Some glaze recipes call for "feldspar" and others will specify what type of
feldspar to use, such as custer, soda, or potash. Normally, to which are
they referring? I wonder also what are the qualities of each and what do
they do in a glaze or if you substituted one for the other, how would they
affect the glaze?
Lynn in L.A. (lower Alabama) -- nice weather, cool evenings and already
mowing grass.
GURUSHAKTI@aol.com on wed 17 apr 96
Dear Lynn:
Feldspars have varying proportion of sodium, potassium, aluminina and silica
with at times traces of calcium. There are lithium feldspars, soda feldspars
and potash feldspars.
They are not all interchangeable in glazes.
A good way to see this is to make for yourself is a feldspare melt slab.
Here's how you do it: Make a five by nine slab of porcelain or
whitestoneware about three eights of an inch thick. You can bisque fire this.
Then take a thimble or one of those porcelain laboratory measures that looks
like a thimble and fill it with a feldspar. Tap firm enough to compress the
powdered feldspar but not so firm that it won't release. Invert the thimble
on the bisque fired slab. Make sure to keep your little mounds of feldspar
about an inch from the ege and about inch from each other. Mark with the
name in front of each spar, near the edge making sure again to leave enought
room because some of these will melt more than others. Do this with every
feldspar you can buy, beg, borrow or trade. It is a wonderful reference tool.
You will see the different in the meld from one to another as well as the
difference in the fire color as well as which one would make the best crackle
glaze. Some will be nice and white and others like Kingman may show a light
grey color.
You will see that Cornwall stone and G200 will melt far earlier than Custer
and Kingman will still be sitting very erect when the others have slumped.
That is if you can find some Kingman.
This was something my glaze instructor Vivika Heino had us to in glaze class.
It is a great idea to do this with all your ceramic materials. She also had
us make little elbow pots by taking a round of porcelain clay about three
and a half to four inches in diameter and about a quarter of an inch to three
eights of an inch thick. Hold it in the palm of your right hand (or left) and
lightly with your hand cupped pound it againt you left elbow (make sure your
arm in bent so you get a good pointy elbow.<> You can bisque these and
then place a full teaspoon or more of every glaze making material you can
find in each one. Mark the outside of the elbow pots near the top to identify
later. Do this with frits and even the dirt from your garden. Fire these to
top temperature. I did mine at cone ten. It will show you the fired coloreand
melt of all the materials you are using in your glazes. You will be amazed at
some of the results. Make sure you put the soda ash in a pretty thick elbow
pot or it will eat its way right through!
Once fired you can glue the elbow pots to a large board and have it as a
reference and teaching tool for yourself and others.
Have fun!
Ron Roy on wed 17 apr 96
>----------------------------Original message----------------------------
>Some glaze recipes call for "feldspar" and others will specify what type of
>feldspar to use, such as custer, soda, or potash. Normally, to which are
>they referring? I wonder also what are the qualities of each and what do
>they do in a glaze or if you substituted one for the other, how would they
>affect the glaze?
>
>Lynn in L.A. (lower Alabama) -- nice weather, cool evenings and already
>mowing grass.
Big question Lynn,
Let me answer a small part of it. Feldspars are a natural (read cheap)
source of sodium and potassium for glazes. All contain various amounts of
each. If more potash than sodium then call it a potash spar and visa-versa.
If a glaze (with North American materials) calls for spar more than likely
it will be a potash spar. Potasium is the flux of choice from come 8 up
because sodium is volatile at high temps - that is unless you want to glaze
the inside of your kiln over time. The two pot spars in common use are G200
and Custer - they are very close in makeup with the G200 having. perhaps a
slight edge in melting power - at least according to the analyses I am
currently using. G200 has a higher expansion than Custer (more silica) so a
substitution of Custer for G200 may cure some marginal crazing problems.
When I add the sodium and potash together (KNaO) and compare spars I come
up with a question. Why would anyone use a soda spar unless they were
looking for more sodium? Note: more flux for the buck with pot spars
Pot Spars
G200 13.68 KNaO
Custer 13.10
Soda Spars
F4 11.7
C6 12.1
Neph Sy 14.4 - hi flux but 68 percent sodium.
One of the basic experiments which told me more than any numbers was
melting the various spars - at whatever temp you work - I did mine at 8 and
10 but even at cone 6 you will see the differences.
Ron Roy, Toronto, Canada
LBlos72758@aol.com on thu 18 apr 96
Dear Lynn,
If a feldspar is not specified, I first try a potash such as Custer. I can
also make a 100 g batch with a soda spar such as F-4. Just to see which I
like better.
Linda
Ithaca, NY
tmartens on sun 25 apr 99
I posted a glaze ^ 5 to ^6 Celadon like. Since I only have access to one
potash spar, I could not answer a question someone asked.
The chemical analysis of my feldspar is:
SiO2 65.50 %
AL2O3 18.70
K2O 12 to 12.5
Na2O 2.3 to 2.6
Fe2O3 O.O5
MgO O.O3
CaO O.11
P2O5 O.O4
TiO2 O.O2
Y2O3 2Oppm
Ce2O3 3Oppm
La2O3 30ppm
LOI at 1000 C O.35%
The recipe I posted was :
Birke's Celadon ^5 to ^6
Feldspar 58
Whiting 17
Flint 14
Ball Clay 6
Zinc Oxide 5
Copper Oxide 1
The question is, Feldspar obtainable in North America would be the
most suitable?
TIA
Toni Martens Durban South Africa
Tom Buck on mon 26 apr 99
Ms Martens:
You ask for a replacement feldspar for your South African one with 12+%
K2O. Well, in No. America there is no duplicate but the closest (at 10+%
K2O) are Custer fs (west) and G-200 fs (east). These two have slightly
higher Al2O3 and SiO2 than yours. So perhaps No. American potters may have
to adjust the C5/6 Oxidation Celadon recipe on some claybodies.
Good pots.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada). mailing address: 373
East 43rd Street,
Hamilton ON L8T 3E1 Canada
Fay & Ralph Loewenthal on tue 27 apr 99
Toni from Durbs asked about the feldspar. The closest I could
find was Buckingham Feldspar which is:
SiO2 65.58
Al2O3 19.6
K2O 12.44
Na2O 2.56
Fe2O3 0.01
MgO 0.2
CaO 0.16
Ignition loss is 0.32
This comes from Chappell's book 1977 edition, so the formula
may have changed over the last 20 years. Hope this helps
from Ralph in PE SA.
Edouard Bastarache on wed 28 apr 99
------------------
Hello Toni, Fay =26 Ralph,
Buckingham Spar was mined in Quebec, Canada
and the mine was closed many years ago.
In North America you can substitute for it by Custer Spar.
Later,
Edouard Bastarache
edouardb=40sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/=7Eedouardb/
-----Message d'origine-----
De : Fay =26 Ralph Loewenthal =3Cfayralph=40intekom.co.za=3E
=C0 : CLAYART=40LSV.UKY.EDU =3CCLAYART=40LSV.UKY.EDU=3E
Date : 27 avril, 1999 07:43
Objet : Feldspar question
----------------------------Original message----------------------------
Toni from Durbs asked about the feldspar. The closest I could
find was Buckingham Feldspar which is:
SiO2 65.58
Al2O3 19.6
K2O 12.44
Na2O 2.56
Fe2O3 0.01
MgO 0.2
CaO 0.16
Ignition loss is 0.32
This comes from Chappell's book 1977 edition, so the formula
may have changed over the last 20 years. Hope this helps
from Ralph in PE SA.
Michael Wendt on fri 5 dec 03
Roger Kaufman from the Moose Creek Feldspar Co asked me a question I need to
pass along to the group.
Is there a market for the high grade Moose Creek Spar which has 18%
Potassium plus 2% Sodium?
I answered off the top of my head that such a high alkali content would
permit us to make glazes with more clay to keep non plastics in suspension.
It turns out that most spar producers blend down the level of alkali to
match the 12% general analysis of the competition.
Any thoughts on this would be greatly appreciated as he is coming by
December 11th for a visit and I would love to share your input with him.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, ID 83501
wendtpot@lewiston.com
www.wendtpottery.com
Hank Murrow on sat 6 dec 03
On Dec 5, 2003, at 7:33 PM, Michael Wendt wrote:
> Roger Kaufman from the Moose Creek Feldspar Co asked me a question I
> need to
> pass along to the group.
>
> Is there a market for the high grade Moose Creek Spar which has 18%
> Potassium plus 2% Sodium?
Dear Michael;
Potters who use glaze software are always looking for a high K2O
material. When you think of it, there are very few non-soluble sources
of Potassium available.
Anyone in search of a celadon would be well served by such a material.
The 18% figure for Potassium in the Moose Creek source would permit
glaze formulations unobtainable until now.
I have used the coarse sample in my testing after grinding it down to
fine powder, and can attest to its unique quality.
Sign me up, and I encourage others to try a sample as soon as 300 mesh
samples becomes available.
Cheers, hank in Eugene
www.murrow.biz/hank
Alex Solla on sat 6 dec 03
As much as I know us glaze hounds would love to play with this stuff... it wont happen unless one of the bigger distributors decides to carry it. I love feldspar but I dont need a truck full. But if I could call up Tuckers or Laguna or Standard.... that's a different story. Then I would be ONE HAPPY CAMPER! Hey, that's what I want for christmas. A big ol bag of high pottasium spar. My daughter would die laughing.
cheers,
Alexander Solla
Cold Springs Studio
4088 Cold Springs Road
Trumansburg, NY 14886
Hank Murrow wrote:
On Dec 5, 2003, at 7:33 PM, Michael Wendt wrote:
> Roger Kaufman from the Moose Creek Feldspar Co asked me a question I
> need to
> pass along to the group.
>
> Is there a market for the high grade Moose Creek Spar which has 18%
> Potassium plus 2% Sodium?
Dear Michael;
Potters who use glaze software are always looking for a high K2O
material. When you think of it, there are very few non-soluble sources
of Potassium available.
Anyone in search of a celadon would be well served by such a material.
The 18% figure for Potassium in the Moose Creek source would permit
glaze formulations unobtainable until now.
I have used the coarse sample in my testing after grinding it down to
fine powder, and can attest to its unique quality.
Sign me up, and I encourage others to try a sample as soon as 300 mesh
samples becomes available.
Cheers, hank in Eugene
www.murrow.biz/hank
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Craig Martell on sat 6 dec 03
At 07:33 PM 12/5/2003 -0800, you wrote:
>Is there a market for the high grade Moose Creek Spar which has 18%
>Potassium plus 2% Sodium?
Hello Michael:
Yes, I think there would be a very good market for this high grade
spar. So far, the only feldspar that's been at even12% was Kingman and
that's long gone. Well, Ok, you could get some Norfloat from Norway.
One type of glaze that this spar would benefit is iron blues. High
potassium glazes favor this nice sky blue. We can make these glazes with
spars that are available but when you push the percentage up to the point
that the blue is there, you've also added a fair amount of sodium and glaze
fit becomes a problem. With an 18% K2O spar it would be a lot easier to
adjust glaze expansion because the sodium would be lower.
Claybodies would benefit too. You could add more clay to stoneware and
porcelain bodies with a spar that's higher in K2O. I think that this spar
would be a real asset to folks making cone 6 porcelains.
I give this idea a hearty thumbs up.
regards, Craig Martell Hopewell, Oregon
Ron Roy on sun 7 dec 03
Sounds like 300M might be on the fine side - we need to consider solubility
I think - 200M would be more than enough.
I'll be glade to test some.
RR
>> Roger Kaufman from the Moose Creek Feldspar Co asked me a question I
>> need to
>> pass along to the group.
>>
>> Is there a market for the high grade Moose Creek Spar which has 18%
>> Potassium plus 2% Sodium?
>
>Dear Michael;
>
>Potters who use glaze software are always looking for a high K2O
>material. When you think of it, there are very few non-soluble sources
>of Potassium available.
>
>Anyone in search of a celadon would be well served by such a material.
>The 18% figure for Potassium in the Moose Creek source would permit
>glaze formulations unobtainable until now.
>
>I have used the coarse sample in my testing after grinding it down to
>fine powder, and can attest to its unique quality.
>
>Sign me up, and I encourage others to try a sample as soon as 300 mesh
>samples becomes available.
>
>Cheers, hank in Eugene
>www.murrow.biz/hank
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Fredrick Paget on sun 7 dec 03
> >Is there a market for the high grade Moose Creek Spar which has 18%
> >Potassium plus 2% Sodium?
>
>Hi Michael:
You bet. You can put me down for a couple of 50 pound bags.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
David Hendley on sun 7 dec 03
Yes, I would like to have a feldspar with a higher total flux component,
for the reason you state.
This would be especially useful when formulating slip-glaze recipes.
Availability is the big question. I would not pay a premium to
have small quantities shipped to me. It would have to be available
for a comparable cost to Custer feldspar at my supplier
(Trinity Ceramic Supply in Dallas).
David Hendley
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
> Is there a market for the high grade Moose Creek Spar which has 18%
> Potassium plus 2% Sodium?
>
> I answered off the top of my head that such a high alkali content would
> permit us to make glazes with more clay to keep non plastics in
suspension.
> It turns out that most spar producers blend down the level of alkali to
> match the 12% general analysis of the competition.
Andrew Sugden on wed 10 dec 03
On Sun, 7 Dec 2003 18:58:04 -0600, David Hendley wrote:
>Yes, I would like to have a feldspar with a higher total flux component,
>for the reason you state.
>This would be especially useful when formulating slip-glaze recipes.
>Availability is the big question. I would not pay a premium to
>have small quantities shipped to me. It would have to be available
>for a comparable cost to Custer feldspar at my supplier
>(Trinity Ceramic Supply in Dallas).
>
>David Hendley
>david@farmpots.com
>http://www.farmpots.com
>
>
>----- Original Message -----
>> Is there a market for the high grade Moose Creek Spar which has 18%
>> Potassium plus 2% Sodium?
>>
>> I answered off the top of my head that such a high alkali content would
>> permit us to make glazes with more clay to keep non plastics in
>suspension.
>> It turns out that most spar producers blend down the level of alkali to
>> match the 12% general analysis of the competition.
>
>__________________________________________________________________________
____
>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.
I would be very cautious as whatever the material is with an anlysis like
that it's not feldspar.
Pure potash feldspar, which nature has not left us with and no refining
process can achieve, has a total K2O of 16.9% whilst pure soda 'spar is
has 11.8%.
The pureset K'spar I know of is produced from a German deposit with about
14.5% K2O.
Anyway if someone sends me a sample I can analyse it, XRf & XRD.
That's it.
Andrew
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