Jorge Nabel on wed 17 apr 02
Hello Clayarters.I am needing your intuition and your knowledge. Things are
like this:Im moving from a shopmade earthenware to a make by yourself cone 6
Ox/reduction red stoneware .This is a natural clay and its very soft and
plastic for throwing but I feel need antiplastic somehow.
Fired to cone 8 to try it and its OK with small thrown pieces, but a square
plate that had some curves on its endings became flat. That was a real cone
8 with a long hold.
It has 4% Fe, Al2O3 about 24% and my provider says it vitrifies at 1250C.
First wanted to add grogg, but its not available a good grog.
So I thought to mix 10% Alumina mesh 120 but got aware that its imported and
it costs 9 times the price of the clay.
Somebody told me to add silica mesh 325, other told to add felspar, and
another one told me to add Kaolin.
I know I have to make some test.So where do I begin with?With the plain clay
measuring absorption and contraction at ^6? Adding all the suggestions and
making test tiles of each?....
Thanks in advance.
Jorge Nabel
alfareriaurbana@sion.com
Snail Scott on thu 18 apr 02
At 11:18 PM 4/17/02 -0300, you wrote:
>...This is a natural clay and its very soft and
>plastic for throwing but I feel need antiplastic somehow.
>First wanted to add grogg, but its not available a good grog.
Bad grog works pretty well, too.
My favorite ^6 red stoneware had 30% grog
by weight, and I always used the Muddox
Buff grog, which is nothing but ground-up
firebrick. Manufacturers seem to avoid it
because the size is irregular and it's
full of undefined impurities, but I liked
the wide range of particle sizes, the
price, and especially the color - yellowish
and much nicer than that grey/white (and
expensive) silica grog. And I never had
any problems with impurities except some
occasional iron spotting, if you call that
a problem at all. I figure it did its job
in preventing warpage during making and
during firing, and in helping the work
dry evenly. Good enough for me.
-Snail
Andrew B Buck on wed 1 may 02
> At 11:18 PM 4/17/02 -0300, you wrote:
>...This is a natural clay and its very soft and
>plastic for throwing but I feel need antiplastic somehow.
>First wanted to add grogg, but its not available a good grog.
If grog is not available to you, make your own. Take the claybody you
want to modify, dry it out, bust it up into powder, fire it to the glaze
temperature you fire at, bust it up some more, and sieve it through a
screen the size you want the grog to be. When you add it to the clay
body, it will not change the color of the finished product or change the
way the glazes work with the clay body. It will change the plasticity
and lower the shrinkage of the clay body.
Andy Buck
Raincreek Pottery
Port Orchard, Washington
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Ron Roy on tue 7 may 02
I think this is a good suggestion Andy - depends on how much you need I
suppose. I do it - save my trimmings and roll em - sieve to different sizes
and fire to bisque temperature.
There are many additions that would also help - silica for one, kyanite and
pyrophilite are others - feldspar is another - it deos get tricky when high
firing but I am assuming this is low fire stuff???
RR
>> At 11:18 PM 4/17/02 -0300, you wrote:
>>...This is a natural clay and its very soft and
>>plastic for throwing but I feel need antiplastic somehow.
>>First wanted to add grogg, but its not available a good grog.
>
>If grog is not available to you, make your own. Take the claybody you
>want to modify, dry it out, bust it up into powder, fire it to the glaze
>temperature you fire at, bust it up some more, and sieve it through a
>screen the size you want the grog to be. When you add it to the clay
>body, it will not change the color of the finished product or change the
>way the glazes work with the clay body. It will change the plasticity
>and lower the shrinkage of the clay body.
>
>Andy Buck
>Raincreek Pottery
>Port Orchard, Washington
Ron Roy
RR #4
15084 Little Lake Road
Brighton
Ontario
Canada - K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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