Michael McDowell on fri 9 dec 11
Dear Ron,
The discussion of the change in Custer Feldspar seemed to have diverged a
bit with Lee's rant on the subject of using chemical analyses and glaze
software. Either I lost the thread or it was dropped when the usefulness of
that approach was brought into question.
I was hoping that someone, most likely you, would have determined whether
this change would be a permanent or a transitory one. I'm remembering the
difficulties many of us had dealing with the souring of Kingman Feldspar as
that vein played out in the mid-eighties. Back then the lack of glaze
software made for many a headache for the calculation averse among us.
Empirical testing is the final stage of any adjustment procedure, but the
ready availability of glaze software and updated chemical analyses certainl=
y
aid us in the choice of what tests to try. Still, one wonders if the Custer
vein has soured for good or if they will attempt to redirect the mining
efforts to bring the output back to the old target values. Any word on that=
?
Michael McDowell
Whatcom County, WA, USA
michael@mcdowellpottery.com
http://www.McDowellPottery.com
Michael Wendt on sat 10 dec 11
I'm not Ron but I have a suggestion...
Go to a fabric store and buy a thimble.
I spray the inside with WD40 and lightly wipe it.
Spread the feldspar onto a sheet of plastic and
mist it with water lightly.
Pack the thimble with the feldspar and scrape
it level with the end of the thimble.
Place the thimble on a clay scrap opening down.
Tap the sides of the thimble lightly to get the
contents to come out and stay on the clay substrate.
Let dry and fire in the next load with a set of cones
on the substrate next to the fusion button.
With a sharpie, label the substrate with date and
batch data and glue the cone pack to the substrate.
Each time you order a melter like Feldspar, before
you use it, test it and compare the fired test to earlier
examples of the same product.
Here's why:
using line blends you can compensate for variation in
batches. If one batch melts more than your standard
sample you can either blend in more silica to the next
fusion button test to get the same spread and slump rate
or... if it melts less than your standard sample
you can add a flux like Nepheline Syenite to increase
melting and slump rate.
While time consuming, do consider the cost of
the loss of all the work done if this kind of test is
not carried out.
Regards,
Michael Wendt
Michael McDowell wrote:
Dear Ron,
The discussion of the change in Custer Feldspar seemed to
have diverged a
bit with Lee's rant on the subject of using chemical
analyses and glaze
software. Either I lost the thread or it was dropped when
the usefulness of
that approach was brought into question.
I was hoping that someone, most likely you, would have
determined whether
this change would be a permanent or a transitory one. I'm
remembering the
difficulties many of us had dealing with the souring of
Kingman Feldspar as
that vein played out in the mid-eighties. Back then the lack
of glaze
software made for many a headache for the calculation averse
among us.
Empirical testing is the final stage of any adjustment
procedure, but the
ready availability of glaze software and updated chemical
analyses certainly
aid us in the choice of what tests to try. Still, one
wonders if the Custer
vein has soured for good or if they will attempt to redirect
the mining
efforts to bring the output back to the old target values.
Any word on that?
Michael McDowell
Whatcom County, WA, USA
michael@mcdowellpottery.com
Steve Slatin on sat 10 dec 11
Michael -- =3D0A=3DA0=3D0AI'm with you.=3DA0 I can use the Custer I have, a=
s it's t=3D
he old stuff, but I *need* to know what I'm=3D0Agetting when I buy a new ba=
g.=3D
=3DA0 Or else I need to switch to blending Minspar and G-200HP=3D0A(I don't=
act=3D
ually blend them together; I use the two together to sub for the old G-200 =
=3D
and =3D0Aaltering that sub to 'hit' the Custer numbers would be pretty easy=
.)=3D
=3D0A=3DA0=3D0ABut=3DA0understanding what we're dealing with is necessary t=
o a know=3D
ledge-driven approach to=3D0Aglaze formulation/mixing.=3DA0 I just moved to=
a n=3D
ew city, got a new (and very different) kiln and=3D0Aam resigned to using n=
ew=3D
clays.=3DA0 I don't need to also have new glaze materials.=3D0A=3D0ASteve =
Slatin=3D
-- =3D0A=3D0A=3D0AN48.0886450=3D0AW123.1420482=3D0A=3D0A=3D0A_____________=
______________=3D
_____=3D0A=3D0A=3D0ADear Ron,=3D0A=3D0AThe discussion of the change in Cust=
er Feldspa=3D
r seemed to have diverged a=3D0Abit with Lee's rant on the subject of using=
c=3D
hemical analyses and glaze=3D0Asoftware. Either I lost the thread or it was=
d=3D
ropped when the usefulness of=3D0Athat approach was brought into question.=
=3D0A=3D
=3D0AI was hoping that someone, most likely you, would have determined whet=
he=3D
r=3D0Athis change would be a permanent or a transitory one. I'm remembering=
t=3D
he=3D0Adifficulties many of us had dealing with the souring of Kingman Feld=
sp=3D
ar as=3D0Athat vein played out in the mid-eighties. Back then the lack of g=
la=3D
ze=3D0Asoftware made for many a headache for the calculation averse among u=
s.=3D
=3D0A=3D0AEmpirical testing is the final stage of any adjustment procedure,=
but=3D
the=3D0Aready availability of glaze software and updated chemical analyses=
c=3D
ertainly=3D0Aaid us in the choice of what tests to try. Still, one wonders =
if=3D
the Custer=3D0Avein has soured for good or if they will attempt to redirec=
t =3D
the mining=3D0Aefforts to bring the output back to the old target values. A=
ny=3D
word on that?=3D0A=3D0AMichael McDowell=3D0AWhatcom County, WA, USA=3D0Ami=
chael@mc=3D
dowellpottery.com=3D0Ahttp://www.McDowellPottery.com
Paul Herman on sat 10 dec 11
Hi Michael and All,
A few days ago I did some fusion buttons of the various feldspar
materials around my shop, of course with special attention paid to
Custer feldspar. Luckily, I had two pallets of Custer, one bought
about a year ago, and one from maybe two-three years ago. I could tell
which pallet was older by the layer of dust on the corners of the
sacks. They show a small but definite difference in the fired fusion
button, with the older batch melting more than the newer one.
For what it's worth, the other feldspars were as follows:
Nepheline Syenite melted the most, a nice smooth, crazed button.
F-4 melted the next most, also smooth and slumped, but not crazed.
G-200 melted the next most, also slumping.
G-200HP didn't melt as much as G-200 and didn't slump much, but had a
clearer glass rather than white glass.
My home dug feldspar melted about as much as G-200HP, but was clearer
still and had small iron specks.
Even the old Custer sample was somewhat stiff and white, but the newer
ones were more so.
I think if I use the older pallet of Custer, the clay body will
probably behave more "normally", so that's what I will be trying. Also
I'm going to get a pallet of the new G-200 HP and start using it in
the clay body. Perhaps I can blend some with the new Custer and get a
satisfactory result. Now I'm sitting on about 900 pounds of the
questionable stuff.
Good luck to all in getting good feldspar,
Paul Herman
Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/
On Dec 9, 2011, at 9:37 PM, Michael McDowell wrote:
> Dear Ron,
>
> The discussion of the change in Custer Feldspar seemed to have
> diverged a
> bit with Lee's rant on the subject of using chemical analyses and
> glaze
> software. Either I lost the thread or it was dropped when the
> usefulness of
> that approach was brought into question.
>
> I was hoping that someone, most likely you, would have determined
> whether
> this change would be a permanent or a transitory one. I'm
> remembering the
> difficulties many of us had dealing with the souring of Kingman
> Feldspar as
> that vein played out in the mid-eighties. Back then the lack of glaze
> software made for many a headache for the calculation averse among us.
>
> Empirical testing is the final stage of any adjustment procedure,
> but the
> ready availability of glaze software and updated chemical analyses
> certainly
> aid us in the choice of what tests to try. Still, one wonders if the
> Custer
> vein has soured for good or if they will attempt to redirect the
> mining
> efforts to bring the output back to the old target values. Any word
> on that?
>
> Michael McDowell
> Whatcom County, WA, USA
> michael@mcdowellpottery.com
> http://www.McDowellPottery.com
Richard White on sat 10 dec 11
I am not Ron either, but here is my take on it. At some point in the rece=
=3D
nt
past, the chemical composition of Custer changed. They didn't put out a
press release that I know of, they way the G-200 folks did when that
changed. They apparently just changed the data sheet on their website to
show the new numbers. Caveat Emptor, I guess. Comparing traditional vs. t=
=3D
he
new numbers, the new Custer has, among other things, 7% potassium, 15%
alumina, and 75% silica. The old Custer had 10% potassium, 17% alumina, a=
=3D
nd
69% silica. That's a fairly significant reduction in potash and in total
fluxes, and the balance of silica to alumina is changed. All other things=
=3D
equal, the glaze will melt less, and when it does melt it will be higher =
=3D
in
silica which will make it glossier and possibly change the fit to the cla=
=3D
y body.
What to do? In no particular order of priority or desirabilty:
1) Get out your glaze calculation software, enter a new material with the=
=3D
percentages from the Pacer website, and recalculate all your glazes.
2) Do a boatload of line blends to see what you can develop empirically.
3) Figure out a substitution.
In the case a few years ago with G-200, spar from the new mine had a much=
=3D
higher potash content, so they blended it with enough soda spar to temper=
=3D
it
back to the same analysis as previous material. When that got too expensi=
=3D
ve,
they renamed the product to G-200HP (for High Potassium) and advised
customers seeking the old formulation to do their own blending with some
Minspar. Or, many potters just subbed Custer as that was close enough to =
=3D
the
old G-200.
And now Pacer (the maker of Custer) has moved the cheese. But they haven'=
=3D
t
(yet) made any recommendations. So I got out the glaze calculation softwa=
=3D
re
(thank you John and Ron for GlazeMaster, but any of the others will do ju=
=3D
st
as well) and started "mixing" proportions of the new, lower potash, Custe=
=3D
r
with the not-as-new, higher potash, G-200HP to see how much it would take=
=3D
to
temper the new Custer back to the old. It's not a perfect match and I hav=
=3D
e
not tested it extensively yet, but I found that 75% new Custer plus 25%
G-200HP was as close as I could get to the old Custer numbers.
Have at it, and as always, YMMV so test test and test.
dw
Ron Roy on sat 10 dec 11
Hi Michael,
Easy to deal with the doubters by the way - their lack of experience
makes their arguments easy to refute.
Seems a call to Pacer would not be a bad idea.
Someone told me Pacer used to use another spar is order to keep the
analysis from batch to batch close but they don't do that anymore. I
wish I knew the real answer to that one.
I do know the old g200 was mixed to keep the batches close - and when
they stopped doing that they told everyone - the way it should be in
my opinion.
I had heard that Custer went through this sort of thing many years ago
and so I have avoided using custer in my own studio. I think it is
important to know which materials are reliable and which are not - so
we know how to deal with the problematic ones.
Luckily getting accurate analysis at very reasonable cost is easy
these days - I also think that is the most cost effective way to deal
problems of this sort - in this case - adding more custer to get
enough KNaO also gets more alumina and silica - which must be allowed
for.
Glad to send my friends lab test results by the way.
Best regards Michael - RR
Quoting Michael McDowell :
> Dear Ron,
>
> The discussion of the change in Custer Feldspar seemed to have diverged a
> bit with Lee's rant on the subject of using chemical analyses and glaze
> software. Either I lost the thread or it was dropped when the usefulness =
of
> that approach was brought into question.
>
> I was hoping that someone, most likely you, would have determined whether
> this change would be a permanent or a transitory one. I'm remembering the
> difficulties many of us had dealing with the souring of Kingman Feldspar =
as
> that vein played out in the mid-eighties. Back then the lack of glaze
> software made for many a headache for the calculation averse among us.
>
> Empirical testing is the final stage of any adjustment procedure, but the
> ready availability of glaze software and updated chemical analyses certai=
nly
> aid us in the choice of what tests to try. Still, one wonders if the Cust=
er
> vein has soured for good or if they will attempt to redirect the mining
> efforts to bring the output back to the old target values. Any word on th=
at?
>
> Michael McDowell
> Whatcom County, WA, USA
> michael@mcdowellpottery.com
> http://www.McDowellPottery.com
>
Ron Roy on sat 10 dec 11
Hi Paul,
I've been fooling around a bit - if you want to try this substitution
in a glaze or two I think it will work - pretty close to the original
custer - check the ratio and expansion numbers.
Would probably work well in a body but there is some neph sy so use it
quick before the defoccing starts or use epsom salts to keep it all
flocced.
CUSTER SPAR................. 100.00
=3D=3D=3D=3D=3D=3D=3D=3D=3D
100.00
CaO 0.03*
K2O 0.66*
Na2O 0.30*
Fe2O3 0.01
Al2O3 1.04
SiO2 7.14
Si:Al: 6.85
SiB:Al: 6.85
Thermal Expansion: 585.39
Formula Weight: 619.12
Custer low K2O.............. 35.40
G 200 HP.................... 52.00
NEPH SY..................... 9.00
SILICA...................... 3.50
=3D=3D=3D=3D=3D=3D=3D=3D=3D
99.90
CaO 0.06*
MgO 0.00*
K2O 0.65*
Na2O 0.29*
Fe2O3 0.00
Al2O3 1.02
SiO2 7.07
Si:Al: 6.91
SiB:Al: 6.91
Thermal Expansion: 579.96
Formula Weight: 611.80
RR
Quoting Paul Herman :
> Hi Michael and All,
>
> A few days ago I did some fusion buttons of the various feldspar
> materials around my shop, of course with special attention paid to
> Custer feldspar. Luckily, I had two pallets of Custer, one bought
> about a year ago, and one from maybe two-three years ago. I could tell
> which pallet was older by the layer of dust on the corners of the
> sacks. They show a small but definite difference in the fired fusion
> button, with the older batch melting more than the newer one.
>
> For what it's worth, the other feldspars were as follows:
>
> Nepheline Syenite melted the most, a nice smooth, crazed button.
>
> F-4 melted the next most, also smooth and slumped, but not crazed.
>
> G-200 melted the next most, also slumping.
>
> G-200HP didn't melt as much as G-200 and didn't slump much, but had a
> clearer glass rather than white glass.
>
> My home dug feldspar melted about as much as G-200HP, but was clearer
> still and had small iron specks.
>
> Even the old Custer sample was somewhat stiff and white, but the newer
> ones were more so.
>
> I think if I use the older pallet of Custer, the clay body will
> probably behave more "normally", so that's what I will be trying. Also
> I'm going to get a pallet of the new G-200 HP and start using it in
> the clay body. Perhaps I can blend some with the new Custer and get a
> satisfactory result. Now I'm sitting on about 900 pounds of the
> questionable stuff.
>
> Good luck to all in getting good feldspar,
>
> Paul Herman
>
> Great Basin Pottery
> Doyle, California US
> www.greatbasinpottery.com/
>
>
>
>
> On Dec 9, 2011, at 9:37 PM, Michael McDowell wrote:
>
>> Dear Ron,
>>
>> The discussion of the change in Custer Feldspar seemed to have
>> diverged a
>> bit with Lee's rant on the subject of using chemical analyses and
>> glaze
>> software. Either I lost the thread or it was dropped when the
>> usefulness of
>> that approach was brought into question.
>>
>> I was hoping that someone, most likely you, would have determined
>> whether
>> this change would be a permanent or a transitory one. I'm
>> remembering the
>> difficulties many of us had dealing with the souring of Kingman
>> Feldspar as
>> that vein played out in the mid-eighties. Back then the lack of glaze
>> software made for many a headache for the calculation averse among us.
>>
>> Empirical testing is the final stage of any adjustment procedure,
>> but the
>> ready availability of glaze software and updated chemical analyses
>> certainly
>> aid us in the choice of what tests to try. Still, one wonders if the
>> Custer
>> vein has soured for good or if they will attempt to redirect the
>> mining
>> efforts to bring the output back to the old target values. Any word
>> on that?
>>
>> Michael McDowell
>> Whatcom County, WA, USA
>> michael@mcdowellpottery.com
>> http://www.McDowellPottery.com
>
jonathan byler on sat 10 dec 11
where does one get these analyses done? and what is a "reasonable
cost"?
thanks,
jon
On Dec 10, 2011, at 4:20 PM, Ron Roy wrote:
> Hi Michael,
>
> Easy to deal with the doubters by the way - their lack of experience
> makes their arguments easy to refute.
>
> Seems a call to Pacer would not be a bad idea.
>
> Someone told me Pacer used to use another spar is order to keep the
> analysis from batch to batch close but they don't do that anymore. I
> wish I knew the real answer to that one.
>
> I do know the old g200 was mixed to keep the batches close - and when
> they stopped doing that they told everyone - the way it should be in
> my opinion.
>
> I had heard that Custer went through this sort of thing many years ago
> and so I have avoided using custer in my own studio. I think it is
> important to know which materials are reliable and which are not - so
> we know how to deal with the problematic ones.
>
> Luckily getting accurate analysis at very reasonable cost is easy
> these days - I also think that is the most cost effective way to deal
> problems of this sort - in this case - adding more custer to get
> enough KNaO also gets more alumina and silica - which must be allowed
> for.
>
> Glad to send my friends lab test results by the way.
>
> Best regards Michael - RR
>
>
> Quoting Michael McDowell :
>
>> Dear Ron,
>>
>> The discussion of the change in Custer Feldspar seemed to have
>> diverged a
>> bit with Lee's rant on the subject of using chemical analyses and
>> glaze
>> software. Either I lost the thread or it was dropped when the
>> usefulness of
>> that approach was brought into question.
>>
>> I was hoping that someone, most likely you, would have determined
>> whether
>> this change would be a permanent or a transitory one. I'm
>> remembering the
>> difficulties many of us had dealing with the souring of Kingman
>> Feldspar as
>> that vein played out in the mid-eighties. Back then the lack of glaze
>> software made for many a headache for the calculation averse among
>> us.
>>
>> Empirical testing is the final stage of any adjustment procedure,
>> but the
>> ready availability of glaze software and updated chemical analyses
>> certainly
>> aid us in the choice of what tests to try. Still, one wonders if
>> the Custer
>> vein has soured for good or if they will attempt to redirect the
>> mining
>> efforts to bring the output back to the old target values. Any word
>> on that?
>>
>> Michael McDowell
>> Whatcom County, WA, USA
>> michael@mcdowellpottery.com
>> http://www.McDowellPottery.com
>>
Michael McDowell on sun 11 dec 11
Thanks for all the info and advice regarding dealing with the changes in th=
e
feldspars we use.
Fusion button testing does seem to be a prudent step to take. And I suppose
that it would be smart to stock in larger quantities of such ingredients so
that this necessary step can be taken less often.
For me, using commercially prepared clay, there is the second shoe. I need
to adapt to whatever adaptation the commercial supplier makes (or doesn't
make) to try and achieve consistency in their product. "The more we learn,
the less we know we know"... Oh well, I now have plenty to do during the
slow winter months...
Michael McDowell
Whatcom County, WA, USA
michael@mcdowellpottery.com
http://www.McDowellPottery.com
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