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cone 6 claybody evaluation help

updated thu 19 may 05

 

Dean Poole on tue 10 may 05


I found a recipy in a book
32 pv clay
32 ball clay
8 bentonite
8 talc
20 mixed grog

listed as plasticity of 8 on a scale of 1-10
I am looking for a tight clay body less than 1% absobtion at cone 6 that is
warm at cone 6 in reduction so this will need to be altered to fire darker
maby with the adition of iron ox. I know nothing about plastic vitrox in
general or formulating clay for that mater and I need a clay that will throw
and slabroll well. are ther any books that will increase my knollidge on
this subject? Sorry for any misspellings I can't.

Daniel Semler on tue 10 may 05


Hi Dean,

Just venturing down the claybody road myself. I don't know enough to help you
with the body itself, but two references on bodies I've found really helpful
are :

Robert Tichane, Claybodies.
David Beumee's article "HIGH-FIRE STONEWARE AND PORCELAIN" in Studio Potter,
Vol. 32, No. 1, December 2003. Back issues are available I believe, that's how
I got mine.

Neither are aimed at the range you are working in specifically, but there is a
great deal about materials, mixing, testing and so on.

> are ther any books that will increase my knollidge on
> this subject?

Thanx
D




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Ron Roy on wed 11 may 05


Hi Dean,

First of all - that is a lot of bentonite - like 2% is the amount recommend
as a top limit.

When I compare that body with a cone 6 clay fluxed with MgO and KNaO is see
it is way overfired - when I add in the grog it looks more "normal."

You should do some deformation, absorbebcy and shrinkage testing - and try
working with it.

If you need instructions for testing let me know.

Does anyone else do any deformation testing - and how do you do it?

RR

>I found a recipy in a book
>32 pv clay
>32 ball clay
>8 bentonite
>8 talc
>20 mixed grog
>
>listed as plasticity of 8 on a scale of 1-10
>I am looking for a tight clay body less than 1% absobtion at cone 6 that is
>warm at cone 6 in reduction so this will need to be altered to fire darker
>maby with the adition of iron ox. I know nothing about plastic vitrox in
>general or formulating clay for that mater and I need a clay that will throw
>and slabroll well. are ther any books that will increase my knollidge on
>this subject? Sorry for any misspellings I can't.

Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513

Jon Pacini on wed 11 may 05


Greetings All- Hi Dean--- you wrote---
I found a recipy in a book
32 pv clay
32 ball clay
8 bentonite
8 talc
20 mixed grog----


This is a type of formula that was going around years ago here on the west
coast and it can be a disaster waiting to happen.

PV clay that is mined in the high desert of California is a quite variable
material. Itís sort of a cross between plastic kaolin and spar. But it can
be a lot more like spar from time to time and Iíve come across more than one
pallet of that in my QA testing over the years.

Also this is a pretty vitreous formula and that dash of talc may not seem
like much, but coupled with the variable PV, it can really get with it some
times.

Iíd recommend being very careful before I committed my production to this
type of formula.

As for books, you canít do much better than Rhodes, Clay and Glazes for the
Potter or Susan Petersons, The Craft and Art of Clay or F & J Hamers, The
Potters Dictionary of Materials and Techniques.

Best regards
Jon Pacini
Clay Manager
Laguna Clay Co.

Ben Shelton on tue 17 may 05


I like to test for slump/deformation in my clay bodies.
I like to make 6 inch test tiles marked at 5 inches for testing bodies.
I do absorption tests at bisque and at whatever temp the body is intended
for. I also like to support a tile at each end to see if it slumps any.
Then I like to fire a batch to 1 or 2 cones above my intended temp to see
how close to slumping I am.

None of this is extremely scientific at the first go round if I am just
trying to weed out the "best 3 out of 10" or something.

Next round of tests I get really picky.

FWIW I am also working towards a tight cone 6 body but I am firing electric
and have no way to test reduction at the moment. I pan on posting results
when I get my kiln fixed and tests finished.

Dean Poole on wed 18 may 05


Thanks for all the great info on pv clay. By the way I was told by Trinity
clay in Dallas that 4-5% absorption at cone 7 was more durable than a
tighter body but my experience doesn=92t conform to this. All my cone 10 cla=
ys
get tighter than this and my cone 6 clay is 1-2% at cone 6. I purchase all
these from Milehigh in Denver and have not had much trouble with chipping
while traveling to shows. In my search for a cone 6 reduction body I bought
a quantity of buff firing cone 6 clay from Laguna that From the look of the
bottom of my pots conforms to the Dallas numbers and have experienced more
trouble with it chipping during transport.