Harry in Iowa on sun 20 jan 02
Hi All,
I have been told that clay with grog stands up to abuse a little =
better. What is grog and why does it help?
Harry in Iowa
Rick Hugel on mon 21 jan 02
Grog is bisque ware that has been ground up to varying degrees of fineness.
Don't know about the abuse factor, but it is used to reduce shrinkage.
>Hi All,
>
> I have been told that clay with grog stands up to abuse a little
>better. What is grog and why does it help?
>
>Harry in Iowa
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
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>
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>melpots@pclink.com.
Harry in Iowa on mon 21 jan 02
Thanks Craig,
One other thought, do you have to match your grog to your clay?
Stoneware grog for stoneware clay, and so on and so forth?
Harry in Iowa
----- Original Message -----
From: "Craig Clark"
To:
Sent: Monday, January 21, 2002 10:05 AM
Subject: Re: What it grog?
> Harry, grog (aka chamott according to Hamer and Hamer), is a ground up
> fired clay body. The grinding is done in a hammer mill, which is as loud
as
> the name suggests. The idea is to pulverize the fired clay into a powder.
> The powder is then sieved into various sizes, bagged and sold. Buy in 100
lb
> bags if you are making your own clay, it's a lot cheaper that way.
> The percentage that you use in your body will be dictated by the type
of
> firing that you're using the clay for.
> With raku, which is what I'm most familiar with, it's a good idea to
> have a minimum of 10% if you are primarily firing smaller closed forms. If
> you're firing larger, open forms, especially big bowls and platters, then
> upwards of fifteen to twenty percent is needed.
> The reason that grog helps the clay stand up to a little abuse is that
> it opens up the clay body thereby facilitating a more even drying than
> tighter bodies (this helps to cut down on cracking in the drying).
> In the specific case of raku, it helps the clay to withstand the
thermal
> shock that it is subjected to when it is taken from the kiln and put into
> reduction.
> Buy yourself a copy of Frank and Janet Hamers book "The Potters
> Dictionary." It has a great explanation on page 161.
> Craig Dunn Clark
> 619 East 11 1/2 st
> Houston, Texas 77008
> (713)861-2083
> mudman@hal-pc.org
>
Craig Clark on mon 21 jan 02
Harry, grog (aka chamott according to Hamer and Hamer), is a ground up
fired clay body. The grinding is done in a hammer mill, which is as loud as
the name suggests. The idea is to pulverize the fired clay into a powder.
The powder is then sieved into various sizes, bagged and sold. Buy in 100 lb
bags if you are making your own clay, it's a lot cheaper that way.
The percentage that you use in your body will be dictated by the type of
firing that you're using the clay for.
With raku, which is what I'm most familiar with, it's a good idea to
have a minimum of 10% if you are primarily firing smaller closed forms. If
you're firing larger, open forms, especially big bowls and platters, then
upwards of fifteen to twenty percent is needed.
The reason that grog helps the clay stand up to a little abuse is that
it opens up the clay body thereby facilitating a more even drying than
tighter bodies (this helps to cut down on cracking in the drying).
In the specific case of raku, it helps the clay to withstand the thermal
shock that it is subjected to when it is taken from the kiln and put into
reduction.
Buy yourself a copy of Frank and Janet Hamers book "The Potters
Dictionary." It has a great explanation on page 161.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Harry in Iowa"
To:
Sent: Sunday, January 20, 2002 6:53 PM
Subject: What it grog?
Hi All,
I have been told that clay with grog stands up to abuse a little better.
What is grog and why does it help?
Harry in Iowa
____________________________________________________________________________
__
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.
Lee Love on tue 22 jan 02
Grog is also watered Rum. :^)
--
Lee In Mashiko Ikiru@kami.com
"It is not from ourselves that we learn to be better than we are. " -Wendell
Berry-
Snail Scott on tue 22 jan 02
At 07:36 PM 1/21/02 -0600, you wrote:
>...One other thought, do you have to match your grog to your clay?
>Stoneware grog for stoneware clay, and so on and so forth?
If you make your own grog, you could use your same
claybody. (Few people make their own grog, though.)
I suspect that using the same claybody would result
in a grog with less ability to resist warping near
vitrification, so if that is your purpose in using
grog, I'd go with a higher-temperature clay, or
use a commercial grog.
Commercial clays generally use a silicaceous grog
which is very refractory, and will suit any
temperature. It is made in a variety of grit sizes.
Depending on your application, this is the main
factor to consider. Most throwers like finer grog,
while people that handbuild large forms usually
like coarser grog. As with clay particle size,
many people prefer to use a range of grog sizes,
to get the advantages of grog without excessive
coarseness. Ask your supplier what grogs they have
available; most will have at least a couple of
different sizes.
There is also 'buff grog' which is made of ground-
up firebrick. It's much cheaper than the 'proper'
silicaceous grogs, but more irregular in size and
composition. I don't know of any commercial clays
that use it, but I prefer the color of it for
red clays.
-Snail
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