Craig Clark on sun 15 sep 02
It's been awhile but I remember that before we had a Soldner mixer and a
Venco, we used an old cement muller (one with the heavy slow moving blades)
and an old pugger (it did not de-air.) We added the grog, to taste, when we
pugged the clay. THe clay runs with more grog added were appreciably more
stiff than those with less grog. I always thought, though I must admit
mistakenly upon reflection, that the grog was absorbing water. I know what
grog is so this is not what infact was occurring.
Explanations?
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "Snail Scott"
To:
Sent: Sunday, September 15, 2002 10:44 AM
Subject: Re: Size Limits for Grog???
> Ivor wrote:
> >>... Just what are you expecting it to do by adding grog.
> >>Stiffen the clay? Adsorb excess water from a sticky mixture? Have clay
> >>that dries quickly? It will also increase the rate at which clay adsorbs
> >>water as it is thrown.
>
>
> Fred wrote:
> >After reading this I had a thought -- what would happen if the grog were
> >treated with a water repellent like the new "Water Warden"?
>
>
>
> Why? Most grog is already non-absorbent, though it does
> add its surface area for moisture to surround. Groggy
> clay dries (and wets) quickly because grog DOESN'T absorb
> moisture, not because it does. (That, and the micro-
> cracking it causes.) Grog seems to provide 'conduits'
> for moisture to move around it, NOT through it.
>
> -Snail
>
>
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Snail Scott on mon 16 sep 02
At 07:10 AM 9/16/02 -0700, you wrote:
>Grog is not just grog. Crushed firebrick will absorb water. Vitrified
>grogs, such as Ione (no longer produced) will not.
Good point, Paul. When I said that grog is non-absorbent,
I was oversimplifying in a big way. I personally love the
crushed-firebrick grog (like the old Muddox grog - know
any good substitutes?), but since most people (and the
manufacturers) seem to prefer the vitrified silicaceous
grogs, I based my reply on that type. That firebrick
grog absorbs a lot more water than the silicaceous grogs,
mostly (I think) because the irregular, deeply pitted
shapes of the pieces give a much larger surface area,
and the pieces themselves are often honeycombed with
little interstices which will also hold water.
-Snail
Paul Herman on mon 16 sep 02
Craig,
Grog is not just grog. Crushed firebrick will absorb water. Vitrified
grogs, such as Ione (no longer produced) will not.
Speaking of which, I'm looking for a replacement for Ione grog, any
suggestions?
Hardway Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: Craig Clark
> I always thought, though I must admit
> mistakenly upon reflection, that the grog was absorbing water. I know what
> grog is so this is not what infact was occurring.
> Explanations?
> Craig Dunn Clark
Ron Roy on wed 18 sep 02
I preferred the crushed fire brick grog - but the supplier we used
(Maryland) crushed used bricks and that became a problem - like once in a
while the bricks were from a copper smelter and green spots started showing
up through glazes.
Virgin brick grog would be my choice if I could get it - I think it gave
better structure for working and also better "bones" during throwing -
maybe because if the shape of the grains.
RR
> When I said that grog is non-absorbent,
>I was oversimplifying in a big way. I personally love the
>crushed-firebrick grog (like the old Muddox grog - know
>any good substitutes?), but since most people (and the
>manufacturers) seem to prefer the vitrified silicaceous
>grogs, I based my reply on that type. That firebrick
>grog absorbs a lot more water than the silicaceous grogs,
>mostly (I think) because the irregular, deeply pitted
>shapes of the pieces give a much larger surface area,
>and the pieces themselves are often honeycombed with
>little interstices which will also hold water.
>
> -Snail
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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