Paul Herman on tue 21 oct 03
Paul,
The SIZE of the grit you are adding may be different than what the
commercial clay body contains. Fine? How fine? What kind of "grog" is
it, anyway?
One of my clays has 4-6%, another 14%, but it's fine (70 mesh) sand.
That's pretty smooth. Some people add more or less than that. It depends
on what you want. If you want it smoother, use less, or finer mesh size.
Happy mixing,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
From Paul B:
> Is there any kind of standard involved in determining how much grog to add
> to a cone 10 stoneware throwing body? I put 10% fine grog in the first few
> batches i mixed and found it to be quite rough, especially along the rims of
> pots. The commerical body i used for several years definitely had less than
> this because it was much smoother to throw with. I want enough grog to help
> with thermal shock and throwing in general so i thought to cut it to 5% next
> time. I would like to hear how much others are using for the kind of work
> they do, and how their clay holds up during drying and firing. thanks,
> Paul B
> Falmouth, KY
Paul on tue 21 oct 03
Is there any kind of standard involved in determining how much grog to add
to a cone 10 stoneware throwing body? I put 10% fine grog in the first few
batches i mixed and found it to be quite rough, especially along the rims of
pots. The commerical body i used for several years definitely had less than
this because it was much smoother to throw with. I want enough grog to help
with thermal shock and throwing in general so i thought to cut it to 5% next
time. I would like to hear how much others are using for the kind of work
they do, and how their clay holds up during drying and firing. thanks,
Paul B
Falmouth, KY
Craig Dunn Clark on wed 22 oct 03
Paul, what is the type of thermal shock to which you are subjecting your
clay body? Are you doing raku? If so then it has been my experience that 10%
grog in the body is a minimum, and that is for smaller pieces. If you are
getting into doing larger, especially open, forms then the percentage for
consistent results needs to go up in excess of 20%.
When you mix your body try adding a coupla different mesh sizes also.
The variations in the particulate size will enhance thermal capacity of the
body as well. What mesh size are you currently using. You may also consider
using kyanite rather than grog. It works very well. I put in a 35 and 100
mesh into the body I make for larger raku pieces. Works great!
As to the smoothness issue.....bottom line is that you are now
exfoliating your hands each time you throw. Grog feels like it sounds, none
to smooth. That's something you will have to get used to. I've reached the
point where I'm just the opposite. If I don't feel the grit in the body I
don't like the clay all that much. If you are concerned about the smoothness
of the lips just take out your handy dandy chamois cloth and smooth the lip
of the pot before you take it off the wheel.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)8961-2083
mudman@hal-pc.org
----- Original Message -----
From: "Paul"
To:
Sent: Tuesday, October 21, 2003 2:24 PM
Subject: HOW MUCH GROG IN STONEWARE?
> Is there any kind of standard involved in determining how much grog to add
> to a cone 10 stoneware throwing body? I put 10% fine grog in the first few
> batches i mixed and found it to be quite rough, especially along the rims
of
> pots. The commerical body i used for several years definitely had less
than
> this because it was much smoother to throw with. I want enough grog to
help
> with thermal shock and throwing in general so i thought to cut it to 5%
next
> time. I would like to hear how much others are using for the kind of work
> they do, and how their clay holds up during drying and firing. thanks,
> Paul B
> Falmouth, KY
>
>
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Louis Katz on wed 22 oct 03
If you can get grog with little or no fines (dust) than go with a finer
grog or sand. 10% is more than most stonewares, but all is relative
unless the rest of the body is known. While I am sure that there are
those on the list that routinely use 10% this is probably on the high
end.
Louis
On Tuesday, October 21, 2003, at 02:24 PM, Paul wrote:
> .... how much grog to add
> to a cone 10 stoneware throwing body? I put 10% fine grog
David Beumee on wed 22 oct 03
Is there any kind of standard involved in determining how much grog to add
> to a cone 10 stoneware throwing body? I put 10% fine grog in the first few
> batches i mixed and found it to be quite rough, especially along the rims of
> pots. The commerical body i used for several years definitely had less than
> this because it was much smoother to throw with. I want enough grog to help
> with thermal shock and throwing in general so i thought to cut it to 5% next
> time.
Cutting your percetage of added grog to 5% is a good choice to lessen the
roughness. One product that is prevalent in the Denver area is 35 mesh Mulcoa
grog. Another possibility to help with opening your body to help with thermal
shock would be using or increasing the percentage of 35 mesh Hawthorn Bond
fire clay. Also, Laguna sells a clay called C-1 that is coarse enough to help
with thermal shock properties, but what is a simple and standardized test for
thermal shock, and what added percentage of one product or another actually
makes a body that will take thermal shock? Lack of cristobalite growth in your
body is also another contributing factor in creating a stoneware body that
will stand up to oven use, a different but related problem.
David Beumee
Earth Alchemy Pottery
Lafayette, CO
> Is there any kind of standard involved in determining how much grog to add
> to a cone 10 stoneware throwing body? I put 10% fine grog in the first few
> batches i mixed and found it to be quite rough, especially along the rims of
> pots. The commerical body i used for several years definitely had less than
> this because it was much smoother to throw with. I want enough grog to help
> with thermal shock and throwing in general so i thought to cut it to 5% next
> time. I would like to hear how much others are using for the kind of work
> they do, and how their clay holds up during drying and firing. thanks,
> Paul B
> Falmouth, KY
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
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