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crystalline glazes/grinding glaze

updated thu 10 apr 03

 

Cat Yassin on mon 7 apr 03


In a message dated 4/4/2003 10:17:53 AM Central Daylight Time,
wschran@EROLS.COM writes:

> I use three different grinders. One is a silicon carbide wheel on a
> bench grinder to get the big stuff. I then use a silicon carbide disc
> that has a self adhesive back that I attached to a plastic bat and
> use that on my wheel to grind and even out the bottom. I then have a
> diamond impregnated disc, again self adhesive on back, attached to a
> bat and used to get a smooth bottom.
> Bill
>

I have a question about grinding glaze... how do you get it to not look like
it was ground with a grinding wheel? I make little lids for bottles that I
like to glaze the whole lid and when I fire them I place them on the little
prefired clay pieces with the metal spikes. I end up with little pits where
the glaze slightly melted around the spike and I use a grinding wheel to
grind the sharp piece down. Its a tiny spot, but it doesn't look like the
rest of the glaze, nice and shiny. Is that how it looks when Crystalline
glazes are ground on the bottom of pots? Doesn't it look like it was "ground"
on a wheel? Or is there some buffing that needs to happen to polish it off?
Thanks in advance!
-Cat Yassin

Vince Pitelka on mon 7 apr 03


> I have a question about grinding glaze... how do you get it to not look
like
> it was ground with a grinding wheel? I make little lids for bottles that I
> like to glaze the whole lid and when I fire them I place them on the
little
> prefired clay pieces with the metal spikes.

Cat -
I have two suggestions. First, an abrasive flap wheel does a nice job of
polishing up the ground surfaces. Go to the Grainger website at
www.grainger.com and enter 4A194 into the search box for a 6" by 1" 120 grit
flap wheel with a 1" arbor hole, and enter 4A200 for the inexpensive bushing
set you need to match the wheel to your 1/2" or 5/8" bench grinder arbor.
When you use the flap wheel for the first time, soften it's "tooth" by
grinding the surface of an old brick, or the bottom of a scrap high-fired
pot. That way it won't be quite so aggressive when you use it to polish
those glazed surfaces. The finish will not be perfect, but it will be a lot
smoother than what the grinder leaves.

My second suggestion has more to do with personal opinion, but it is an
opinion formulated over thirty five years of studying and making ceramic
objects. I don't like the feeling of a glazed lid against a glazed seat.
It feels like glass against glass. It feels fragile, and it just grates on
my senses. It feels all wrong. I love it when the claybody is exposed at
this point, and you have that delicious feeling of clay against clay. When
the clay is fine-grain, and when it is unglazed, and when the lid fits
properly, it makes for a very satisfying fit, almost like a ground glass
stopper on a piece of chemistry glassware.

So it is your choice. If you want to glaze the lid seat, then the abrasive
flap wheel might help you out. Or you might decide to leave it unglazed.
Good luck -
- Vince

Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/

John Rodgers on tue 8 apr 03


To put a finer finish on the glaze you might try buffing with a buffing
wheel using moist soda. Don't add to much water, as the soda will
dissolve, but add just enough to make a moist paste. The fineness of the
soda crystals will serve as a polish. You might check with some glass
workers and see what they use for polishing glass to remove marks and
scratches.

The soda trick can also be used to remove marks on your car paint as
well. Just be gentle and don't overdo it. Rub by hand using a soft cloth.

Soda is use by archeologists to delicately remove rock from fossilized
bones. They use a tool similar to an airbrush. So the Soda is definitely
a fine abrasive.

John Rodgers
Birmingham, AL


Cat Yassin wrote:

>In a message dated 4/4/2003 10:17:53 AM Central Daylight Time,
>wschran@EROLS.COM writes:
>
>
>
>>I use three different grinders. One is a silicon carbide wheel on a
>>bench grinder to get the big stuff. I then use a silicon carbide disc
>>that has a self adhesive back that I attached to a plastic bat and
>>use that on my wheel to grind and even out the bottom. I then have a
>>diamond impregnated disc, again self adhesive on back, attached to a
>>bat and used to get a smooth bottom.
>>Bill
>>
>>
>>
>
>I have a question about grinding glaze... how do you get it to not look like
>it was ground with a grinding wheel? I make little lids for bottles that I
>like to glaze the whole lid and when I fire them I place them on the little
>prefired clay pieces with the metal spikes. I end up with little pits where
>the glaze slightly melted around the spike and I use a grinding wheel to
>grind the sharp piece down. Its a tiny spot, but it doesn't look like the
>rest of the glaze, nice and shiny. Is that how it looks when Crystalline
>glazes are ground on the bottom of pots? Doesn't it look like it was "ground"
>on a wheel? Or is there some buffing that needs to happen to polish it off?
>Thanks in advance!
>-Cat Yassin
>
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Mac and Judi Buchanan on tue 8 apr 03


Two things I have tried might help a little. Some glazes you can refire in
the bisque to melt them just enough to smooth the marks and the stilts make
much tinier marks in this re-fire. Also the marks are less noticeable if
they are greased with Vaseline. It's not a real "fix" but it does make the
piece look better.
Judi Buchanan in South Mississippi where the clay dust problem was fixed
when the studio roof blew off Sunday night.


. I end up with little pits where
> the glaze slightly melted around the spike and I use a grinding wheel to
> grind the sharp piece down. Its a tiny spot, but it doesn't look like the
> rest of the glaze, nice and shiny.

Fabienne Cassman on tue 8 apr 03


Greetings,

I only have a dremel and I hate grinding especially with it. My thoughts immediately went to prevention. In that light, I have been taking great care to use a lavish amount of the concoction I use between the foot and the _matching_ disposable foot ring (pedestal) so that the glaze does not seep between the two and stick to the bottom of the pot. I think of it as mortar between bricks. So far so good, knock on wood etc, I haven't had one booboo since. It's just a matter of popping the pot off and a minute of smoothing the sharp edge with the dremel. Voila.

Concoction or Pedestal Glue:
2/3 Silica
1/3 Calcined China Clay

Add PVA glue (wood glue) until it's workable. Think between dough and batter for the cooks out there. :)

Fabienne

--
Fabienne http://www.milkywayceramics.com/

WARNING: I cannot be held responsible for the above
because my cats have apparently learned to type.

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Lois Ruben Aronow on wed 9 apr 03


If you're serious about continuing with crystalline glazes, you might
want to invest in a lapidary wheel. It grinds to a really fine
finish, but I believe they are not cheap. =20

I potter friend who fires crystals told me that's what he uses.

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