I.Lewis on wed 15 sep 99
------------------
Dear Cyberclay Companions
In answer to Rick McKinnery's request on behalf of his friend, this seems to=
be
one of those =22How Long is a Piece of String=22 questions. And as the =
Philosophers
among us may say, =22It all depends on what you mean=22. Well, using the =
string
analogy, there are at least three parts to consider. Substance, Dimension =
and
Conformation. What can it be made from? How big is big? How complex are the
design elements?
The quick answer is pretty simple. Look at the work of others, ask what they
use, consider their technique and then, imitate. An acquaintance of mine =
makes a
good living constructing pots well over the upper limit given in the =
posting. He
uses the coil and throw method and a strong raku body. Another made vases =
from
white porcelaneous stoneware using the multiple thrown part assembly and I =
have
met several others who can pull up well over thirty inches from average
commercial clays. Many potters resort to heating the clay to firm it up =
before
continuing. However, these solutions do not address the basic issues of what=
is
the best clay body for throwing tall and thin. What sort of clay did Toni =
use in
her enthusiasm to throw tall?
At the risk of being howled down I would suggest working from first =
principles
using raw materials. The mixture should incorporate a maximum amount of =
plastic
clay, a minimum of non plastic materials and no natural or synthetic
plasticisers. Look at mineral analyses as well as oxide content in making
choices. Regard a high Na/K oxide content as providing the flux and try to =
find
something with a SiO2/Al2O3 ratio which is as near as possible to the
theoretical ratio for Kaolinite.. A blend Ball Clay and Kaolin may give a
satisfactory solution. Or look for a ready made body with these properties.
Grog? No=21 Pitchers? No. Sand? No.
Hope this is not too confusing.
Ivor Lewis. In South Oz where they have forecast rain and a max of 18C, but =
the
sky is cloudless and it=92s 21C in the shade.
tmartens on fri 17 sep 99
------------------
To answer one of Ivor's questions, Toni used a very smooth white
=5E6 clay body for that pesky too tall pot and when the clay looked
like it wanted to sag, I 'dried' it off with a metal rib. I find when I use
a heavily grogged body, I might get the size, but the shrinkage can
make beeeeeg pot into medium pot. Can't give clay names that will
be of any use as I am from the other side of the pond.
Toni, thinking very positive thoughts for the folk in the big wind's
passage.
=3E ------------------
=3E Dear Cyberclay Companions
=3E
=3E In answer to Rick McKinnery's request on behalf of his friend, this =
seems to
be
=3E one of those =22How Long is a Piece of String=22 questions. And as the
Philosophers
=3E among us may say, =22It all depends on what you mean=22. Well, using the=
string
=3E analogy, there are at least three parts to consider. Substance, =
Dimension and
=3E Conformation. What can it be made from? How big is big? How complex are =
the
=3E design elements?
=3E
=3E The quick answer is pretty simple. Look at the work of others, ask what =
they
=3E use, consider their technique and then, imitate. An acquaintance of mine=
makes
a
=3E good living constructing pots well over the upper limit given in the =
posting.
He
=3E uses the coil and throw method and a strong raku body. Another made =
vases from
=3E white porcelaneous stoneware using the multiple thrown part assembly and=
I
have
=3E met several others who can pull up well over thirty inches from average
=3E commercial clays. Many potters resort to heating the clay to firm it up =
before
=3E continuing. However, these solutions do not address the basic issues of =
what
is
=3E the best clay body for throwing tall and thin. What sort of clay did =
Toni use
in
=3E her enthusiasm to throw tall?
=3E
=3E At the risk of being howled down I would suggest working from first =
principles
=3E using raw materials. The mixture should incorporate a maximum amount of
plastic
=3E clay, a minimum of non plastic materials and no natural or synthetic
=3E plasticisers. Look at mineral analyses as well as oxide content in =
making
=3E choices. Regard a high Na/K oxide content as providing the flux and try =
to
find
=3E something with a SiO2/Al2O3 ratio which is as near as possible to the
=3E theoretical ratio for Kaolinite.. A blend Ball Clay and Kaolin may give =
a
=3E satisfactory solution. Or look for a ready made body with these =
properties.
=3E Grog? No=21 Pitchers? No. Sand? No.
=3E
=3E Hope this is not too confusing.
=3E
=3E Ivor Lewis. In South Oz where they have forecast rain and a max of 18C, =
but
the
=3E sky is cloudless and it=92s 21C in the shade.
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