Paul Herman on tue 12 apr 05
Hello Jonathan,
Good to see you posting a bit to clayart.
I'm interested in this material, pyrophyllite. My mineralogy book shows
it's chemical formula as Al2(OH)2(Si4O10).
I remember you recomending it a while ago because it has "good juju",
and now recently below you espouse it as "a magic good cure for what
ails you".
There's a bag of the stuff out in my material storage area, but I've not
used it much because I'm unsure of what it will do. Tested in a grolleg
porcelain body, there wasn't much difference except perhaps less
translucency. When you add pryophyllite to a clay body, what
characteristics are you trying to get?
And also, since pyrophyllite contains no potash or soda, how does it
make an acceptable substitute for feldspar? Now I'll admit, good juju
and magic is mighty fine stuff, but my concern is for the "why" rather
than that it apparently works for some needs. In looking at the formula,
I'm wondering, how does it work?
Anything you can explain about pyrophyllite would be much appreciated.
good clay,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: Jonathan Kaplan
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: glazing crazing problem
>Date: Mon, Apr 11, 2005, 11:45 AM
>
> I would think its your clay body for which you might add4-7%
> pyrophyllite which is a magic good cure for what ails you! You can add
> pyrophyllite for parts of the silica/feldspar part of the non-plastics
> of the clay proportion.
>
> You firing schedule is a mite too cautious for me, but if it works for
> you that's fine.
>
> Send me your clay body formula and I'll have a look at it and change it
> for you.
>
> Good Luck!
>
> Jonathan
>
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