Ababi on tue 7 oct 03
Hello Ron
Is it a way to imitate molochite this way?
Ababi
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Tuesday, October 07, 2003 8:36 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Sand vs Grog
Hi William,
I have a "trick" for you!
I make my own grog for certain projects - crush up dried trimmings -
with a
rolling pin - then sieve different sizes. Then bisque it.
that way you have all the advantages of grog but it is the same as the
body
so there is no mis fit possible.
A side advantage - you get lots of dry powdered body - handy if you are
making deflocced slip.
It's a dusty business - the sieving part so it should be done outside or
in
a well ventilated area with a good dust mask on.
RR
>For years I used a fine beach sand in my earthenware and stoneware pots
>(free from an old Cretaceous beach in Northern Colorado). In some of
the
>several native clays that I use it causes cracking in the bisque fire
range.
> This is undoubtedly due to the quartz inversion problem, where the
little
>spheres of primarily quartz initially expand during heating, pushing
the
>clay away. On the way back down the temperature curve they shrink a
bit,
>leaving a small void. All of this movement tends to result in a myriad
of
>tiny cracks that seriously compromise the structural strength of the
clay
>body. And the problem just gets worse as the cracks start running from
>heating and cooling. If the pots make it through the bisque and are
then
>subjected to stoneware temperatures, the problem goes away when the
clay
>sinters and shrinks, effectively erasing the tiny cracks. However,
most of
>my native clays shrink so much that you can see each sand grain on the
>surface of the pot, a not too pleasant decorative effect. I have
abandoned
>the sand and now follow the lead of the prehistoric Pueblo potters of
the
>American Southwest, who avoided using sand and preferred crushed
igneous
>rock (diorite) or ground up pots (grog). Trouble is, grinding up rocks
or
>sherds is hard work with a mano and metate. Anyone out there have a
cheap
>hammer mill (I will accept donations)?
>William A. Lucius, Board President
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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