Brad Carter on mon 28 aug 06
Hi folks,
Is there a significant difference between Tennessee and Kentucky Ball clays?
Can one be subbed for the other in a glaze recipe? Which is OM-4?
Thanks for the help.
Brad Carter
Grass Valley, Calif
David Hendley on tue 29 aug 06
All ball clays are at least slightly different. It doesn't matter
what state they are from.
If you are trying to decide which to use, I suggest you study
a side-by-side analysis sheet. I'm sure the Kentucky Tennessee
Clay Company has the information available online. Some
ball clays have less iron, some have more silica, etc.
In practice, in percentage of 10% or less, I imagine it doesn't
significantly matter what ball clay you use in a glaze recipe.
OM#4 has been the "standard" ball clay in studio ceramics for
generations, so if a glaze recipe called for "ball clay", that is
what I would assume is being asked for. It was mined in Mayfield,
Kentucky, but I've been told that, really, the original OM#4
clay is long gone, and now they mix together different ball clays
to end up with something similar.
David Hendley
Maydelle, Texas
david(at)farmpots(dot)com
http://www.farmpots.com
----- Original Message -----
> Is there a significant difference between Tennessee and Kentucky Ball
> clays?
> Can one be subbed for the other in a glaze recipe? Which is OM-4?
> Thanks for the help.
>
> Brad Carter
> Grass Valley, Calif
steve blankenbeker on tue 29 aug 06
I think the difference is primarily in ultimate
particle size. If I remember correctly, the deposit
is a sheet deposit covering hundreds of miles. Over
the years, certain pits were developed to maximize
certain casting properties for specific customers. I
think the things they looked at were particle size
(correlates with grit or sand content) and lignite
(carbon) present. I was told that the "Old Mine #4"
was exhausted years ago, and that OM4
is simply generic ball clay without a lot of lignite.
In most throwing bodies, especially stoneware, I don't
think there would be much of a noticeable difference.
I will tell you from my clay sales days that I never
saw OM4 being used in any large scale pottery,
whiteware, sanitary ware, or tile shop. If I were
doing porcelain or casting, I think I would notice a
difference. I will also tell you that at one time
Cedar Heights was selling Old Hickory Clay (not sure
of the name) and it was FULL of lignite - lots of
carbon. So if I were to answer your question, it
would be to say all ball clays are potentially
different, and it would probably be best to zero in on
a less generic brand than OM4, because a type being
used by a large customer should be more consistent.
--- Brad Carter wrote:
> Hi folks,
>
> Is there a significant difference between Tennessee
> and Kentucky Ball clays?
> Can one be subbed for the other in a glaze recipe?
> Which is OM-4?
>
> Thanks for the help.
>
> Brad Carter
> Grass Valley, Calif
>
>
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Dannon Rhudy on tue 29 aug 06
Brad asked:
> Is there a significant difference between Tennessee and Kentucky Ball
clays?
> Can one be subbed for the other in a glaze recipe? Which is
OM-4?..........
\
They can be subbed one for another. Differences
depend on the mine/area they come from.
OM4 is Old Kentucky Mine #4. A good clay.
regards
Dannon Rhudy
----- Original Message ----- >
>
> Thanks for the help.
>
> Brad Carter
> Grass Valley, Calif
>
>
____________________________________________________________________________
__
> 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.
>
Edouard Bastarache Inc. on tue 29 aug 06
Hello all,
James Chappell in the first edition of his book
said
you may replace, in glazes, one ball clay by any
other
one.
He said it is another story in clays.
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/potier/172943983/
http://www.flickr.com/photos/potier/172941969/
Lea Holland on wed 30 aug 06
a side-by-side analysis sheet. I'm sure the Kentucky Tennessee
Clay Company has the information available online.>
I notice that the site above is a little vague on its formulas.
Ceramic-materials.com (my favorite resource) has better specifics:
Kentucky #6 Ball Clay
Chemistry
SiO2 63.900
Al2O3 23.600
TiO2 2.100
Fe2O3 0.900
CaO 0.300
MgO 0.300
K2O 0.600
Na2O 0.100
Volatiles
LOI 8.200
Tennessee #1 SGP
Chemistry
CaO 0.300
K2O 1.200
MgO 0.300
Na2O 0.200
TiO2 1.500
Al2O3 28.100
SiO2 57.400
Fe2O3 0.800
Volatiles
LOI 10.200
The above formulas are for only one of many types of eacy clay. The
chemistry order is different, but the formulas are close...
Lea in Memphis
Ivor and Olive Lewis on thu 31 aug 06
Dear Lea Holland,=20
Thank you for posting those percentage assays of molecular oxides for =
Ball Clays.
Of greater interest to me would be their compositions expressed as =
percentages of mineral compounds. Knowing how much residual Muscovite, =
Ilmenite, Orthoclase as well as Quartz and Kaolinite helps to predict =
their behaviour both in clay batches as well as glaze ingredients.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Dave Finkelnburg on thu 31 aug 06
Ivor,
Your questions are appropriate for many parts of
the world, but are not so pertinent in the US.
The principal clay mineral in ball clays of the
Mississippi River drainage of the US is kaolinite.
Virtually all US ball clays are found in a long arc
along the West slope of the Appalachian Mountains.
These are kaolins that have been transported by
erosion processes and are typically contaminated by
very fine quartz sand and organic materials. If you
make the simplifying assumption that all alumina
present in the chemical analysis is kaolin, and
calculate the corresponding proportion of silica, then
subtract that from the total silica in the analysis,
you get an idea of the amount of quartz. From a clay
body standpoint this is a very useful piece of
information.
So I suggest for clay body use comparing the
amounts of silica and alumina in the ball clay
analyses first. Next I would look at LOI as an
indicator of organics present--they aid plasticity and
green strength.
Specific surface area (SSA, square meters/gram), if
you can get it, is also useful. The higher the SSA,
the greater the shrinkage.
Feldspar (orthoclase) and mica (muscovite) are not,
to my knowledge, commonly found in significant levels
in American ball clays.
All the best,
Dave Finkelnburg
--- Ivor and Olive Lewis
wrote:
> Of greater interest to me would be their
> compositions expressed as percentages of mineral
> compounds. Knowing how much residual Muscovite,
> Ilmenite, Orthoclase as well as Quartz and Kaolinite
> helps to predict their behaviour both in clay
> batches as well as glaze ingredients.
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Ivor and Olive Lewis on fri 1 sep 06
Dear Dave Finkelnburg,=20
That is a good way to sum up the basic composition.
Some years ago I did a study of the Salt glaze process. One of the =
things that I found out was that during salting researchers had =
collected significant quantities of Potassium Chloride from the effluent =
gases. In fact this was so important that in WWI is was used as a way of =
providing feedstock for the manufacture of explosives.=20
When you do the calculations, that 1.2% K2O in the Tennessee Ball Clay =
becomes a significant quantity if interpreted as Muscovite or =
Orthoclase. A similar argument might apply to Fe2O3 and TiO2 being =
present as Ilmenite.
Best regards.
Ivor
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