chip parker on thu 11 dec 97
I'm working in salt, and am developing different salt clay bodies for
the work I want to do, which is large scale once fired pieces, some
wheel thrown, some sculptured, and some molded. I have a few good ones
but I'm looking for one that heavy salts, and works well in all areas of
need. I have many recipes, I'm not sure how to analysis these different
salt clay body formulas to know what to expect, or at least have an idea
to compare and know the diffences and what they will look like.
Also I am using a clay body that works well for sculpture, but it isn't
as plastic as I would like it. How much Ball clay should I add. I
don't really want to change and other aspect of the clay body .
Thanks for any information. I'm out here in the prairie of central
Kansas. Anny
Craig Martell on fri 12 dec 97
At 08:13 AM 12/11/97 EST, Anny wrote:
>----------------------------Original message----------------------------
>I'm working in salt, and am developing different salt clay bodies for
>the work I want to do, I'm looking for one that heavy salts, and works well
in all areas
>I have many recipes, I'm not sure how to analysis these different
>salt clay body formulas to know what to expect, or at least have an idea
>to compare and know the diffences and what they will look like.
Hi Anny:
If you want a claybody to be real compatible with salting, the
silica/alumina ratio should be approaching, or at 5 silica to 1 alumina in
the formula. This will require a bit of calculation. The body should have
enough spar to inhibit the development of cristobalite and promote strength
in the fired pieces too.
After college, I worked with a salt glazer for a short time and his approach
to developing clays was first, fire as many pure clay samples as you could
get in the kiln to determine how they salted. We prepared samples of every
ball clay, kaolin, fireclay we could find. Then you make aesthetic
judgements about color of clay etc. before blending different clays into a
body. Avoid a lot of iron and magnesia as these inhibit salt glaze. With
kaolins, which are high in alumina, you need to adjust the level of silica
in the clay formula.
I usually develop my salt bodies in the redution gas kiln (no salt) before I
subject them to vapor glaze. I salt pure clays first to determine the ones
that may give the effect I'm after before blending and testing in the
non-salt kiln. I get a better idea of how they react to thermal changes etc.
I know this isn't always possible though.
some thoughts, Craig Martell-Oregon
Robert Compton on sun 14 dec 97
Chip
It would help to see the receipt for the body you are using. I
have only been firing in salt and wood for the past 7 years, although I
have potted for a living since 1972. I found that the body I had been
making since the early 70's did not orange peal well, it just got a warm
onion skin surface.
That body was one I developed for my watersculptures and
functional ware and used mullite (12%) instead of grog. It made a
wonderfully strong, chip resistant body, something like industrial
kitchenware. But the high Al from the mullite, which I assume was
responsible for the durability, seemed to be resistant to sodium vapors,
of course this makes sense when you realize high alumina bricks are
great in salt kilns.
Since 1990 when we started giving workshops at our pottery, and
participants need to bring bisqueware to fire in our wood or salt kilns,
I had to refer students to packaged premixed bodies that will work well
in these vaporious atmospheres. I purchased premixed clays (a new
experience for me after mixing my own clay for 20 years) from various
east coast suppliers and found that "Standard" (the company name) #119,
really salts well, one reason being their use of silica sand instead of
grog. This body will give a nice orange peel, and ranges from grey to
light brown depending on reduction. I found the Standard #239, a high
fire body they sell for raku also does well and being white, has is a
nice second salt body to have on hand, and their #153 also does well,
but has a bit more iron and may fire darker.
I must say I am using more salt, orginally about 8
lbs in a 40 cu ft kiln to now using 50 lbs in the same kiln. It is just
a look I am after that requires the heavy salt, and it does wreck havock
on the kiln, but it is a price I will pay to get the result I want.
The body I now make has reduced amouts of alumia, I've added sand, and
reduced the iron content. I use about 25% ball and 30% fireclay, and
find it throws just as good on four foot tall urns as well as teabowls.
I will say that I have enjoyed buying premixed clays, about 1/3 of my
pots are made from 5 different bodies I buy. But to be clear we also
fire raku, pit and gas reduction, so a variety of bodies helps.
I'll be interested in seeing other replys to this thread, hope
everyone who does will explain what look they are working toward and how
much salt they are using to keep it all in context.
Bob
> chip parker wrote:
> >
> > ----------------------------Original message----------------------------
> > I'm working in salt, and am developing different salt clay bodies for
> > the work I want to do, which is large scale once fired pieces, some
> > wheel thrown, some sculptured, and some molded. I have a few good ones
> > but I'm looking for one that heavy salts, and works well in all areas of
> > need. I have many recipes, I'm not sure how to analysis these different
> > salt clay body formulas to know what to expect, or at least have an idea
> > to compare and know the diffences and what they will look like.
> >
> > Also I am using a clay body that works well for sculpture, but it isn't
> > as plastic as I would like it. How much Ball clay should I add. I
> > don't really want to change and other aspect of the clay body .
> >
> > Thanks for any information. I'm out here in the prairie of central
> > Kansas. Anny
>
--
Robert Compton Phone: 802-453-3778
3600 Rt 116 http://homepages.together.net/~rcompton
Bristol, Vermont 05443 rcompton@together.net
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