Kat in the Hat on wed 9 jun 04
David Beumee wrote:
>I'm now working with Dr. Carty to find out why tiny bloats appear in the
(cone 10) fired recycled >clay only, not the original commercially clay.
Dear David
It is my understanding that recycled clay from trimmings, throwing buckets,
etc... contain more
of the smaller finer particles from a clay body. That would in general be
the "clay" particles.
While a clay body is drying, the smaller particles migrate to the surface
and while throwing the slip generated also contains more of the actual clay
(kaolinite) Generally specking this clay matures sooner, it is also more
plastic.
I do sieve analysis using screens that range from a 40 mesh to a 325
mesh. All clay particles go through the screens. In fact from screens 40
to 200 is considered "sand" and screens from 200 to 435 mesh are "silt"
after that it is clay. Screens are not made that fine. (which is why you
have to do a soil texture test - with a soil hydrometer to determine clay
content in a clay body)
Often recycled clay body does not have the same particle
distribution. If the clay company you deal with makes your clay in powder
form, you could purchase that and add a bit of dry to the recycled clay --
this may help with increasing the maturity.
Kat in the Hat
kat@digitalfire.com
-----------------------------
Ivor and Olive Lewis on thu 10 jun 04
Dear Kat in the Hat,
Though I do not doubt the analyses you give I am puzzled by your claim
"While a clay body is drying, the smaller particles migrate to the
surface".
I can understand that when a very fluid mixture of water and clay
there is fractionation with the largest, heaviest and densest
fractions at the bottom of the column and the rarest, lightest and
smallest particles at the top. But I cannot understand how the clay
fraction could move from within a block of prepared clay. Is this
proven fact? If so, what is the mechanism which causes motion from
within the body of a mass of clay to the surface?
I would be pleased if you would explain this phenomenon.
Best regards,
Ivor Lewis. Redhill, South Australia
Potters Council Member
From: "Kat in the Hat"
To:
Sent: Thursday, 10 June 2004 1:49
Subject: Re: recycled clay more mature
> David Beumee wrote:
>
> >I'm now working with Dr. Carty to find out why tiny bloats appear
in the
> (cone 10) fired recycled >clay only, not the original commercially
clay.
>
> Dear David
>
> It is my understanding that recycled clay from trimmings, throwing
buckets,
> etc... contain more
> of the smaller finer particles from a clay body. That would in
general be
> the "clay" particles.
> While a clay body is drying, the smaller particles migrate to the
surface
> and while throwing the slip generated also contains more of the
actual clay
> (kaolinite) Generally specking this clay matures sooner, it is also
more
> plastic.
> I do sieve analysis using screens that range from a 40 mesh to a 325
> mesh. All clay particles go through the screens. In fact from
screens 40
> to 200 is considered "sand" and screens from 200 to 435 mesh are
"silt"
> after that it is clay. Screens are not made that fine. (which is
why you
> have to do a soil texture test - with a soil hydrometer to determine
clay
> content in a clay body)
> Often recycled clay body does not have the same particle
> distribution. If the clay company you deal with makes your clay in
powder
> form, you could purchase that and add a bit of dry to the recycled
clay --
> this may help with increasing the maturity.
>
> Kat in the Hat
> kat@digitalfire.com
> -----------------------------
>
>
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Bruce Girrell on thu 10 jun 04
> 2) ".... 200 to 435 mesh are "silt" after that it is clay .... "
>
> Are you suggesting all particles in a clay body below 435 mesh are clay?
Perhaps I can help. Geologists classify particles by size. There are
boulders, cobbles, pebbles, sand, silt and clay. This size descriptor is
applied regardless of the mineralogical composition. All things from 2 mm to
1/16 mm, for example, are called "sand". Thus, you can have a quartz sand,
but you can also have a lime sand. Likewise, all particles smaller than a
1/512 mm are called clay. [Ref. Principles of Sedimentology, Gerald Friedman
& John Saunders, p. 64]
Bruce "I knew I was keeping that book around for some reason" Girrell
mailtoandrew@FSMAIL.NET on thu 10 jun 04
Hello Kat,
Can you clarify a few questions about your post:
1) .... "While a clay body is drying, the smaller particles migrate to the
surface".....
Can you give further details?
2) ".... 200 to 435 mesh are "silt" after that it is clay .... "
Are you suggesting all particles in a clay body below 435 mesh are clay?
3) "... which is why you have to do a soil texture test - with a soil
hydrometer to determine clay content in a clay body ... "
Together with point 2) suggests that size analysis identifies minerals?
I apologise if Ive misunderstood your post.
Thanks,
Andrew
mailtoandrew@FSMAIL.NET on fri 11 jun 04
Hi Bruce,
I had wondered whether or not Kats post was connected to the soil grading.
But as it seemed, from my perhaps misreading, that the suggestion was made
that minerals were being identifed by size alone I was seeking
clarification before commenting further.
Kat could you elaborate further on you post?
Regards,
Andrew
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