Joan Berkwitz on thu 21 aug 03
Here's a goofy question...can beach cobbles be glazed? They look so =
pretty when wet, and dull when dry. It would be fun to glaze them and =
enjoy their subtle colors. The cobbles on our beach are old =
river-tumbled granite, and sometimes quartz, in a wonderful variety of =
colors, with streaks and chunks and spots.
What would happen if they were fired to 06? If no one thinks that they =
would explode or do something terrible, I'll give it a go. And then is =
it just a matter of finding a clear glaze that will fit?
Joanie
John Rodgers on fri 22 aug 03
Hmmmmm! An interesting experiment you want to undertake.
They may melt, they may explode, or catch fire and burn up. Who knows!!
Suggest a very low, slow initial fire, to allow any trapped moisture to
escape. Be sure rocks are placed in a bowl, plate or something to
protect the shelves if they melt down. Be prepare to deal with noxious
fumes - have a fan ready.
Good luck!
John Rodgers
Birmingham, AL
Joan Berkwitz wrote:
>Here's a goofy question...can beach cobbles be glazed? They look so pretty when wet, and dull when dry. It would be fun to glaze them and enjoy their subtle colors. The cobbles on our beach are old river-tumbled granite, and sometimes quartz, in a wonderful variety of colors, with streaks and chunks and spots.
>
>What would happen if they were fired to 06? If no one thinks that they would explode or do something terrible, I'll give it a go. And then is it just a matter of finding a clear glaze that will fit?
>
>Joanie
>
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steve harrison on fri 22 aug 03
Hi Joanie,
I don't believe that firing your rocks will work very well.
I suspect that when you fire the quartz pebbles, they will either
explode or shatter, either way, they are very likely to dunt (crack) on
cooling. I use this method for breaking up rocks.
The felspar and mica in the granite will most likely partially melt,
but the whole pebble will crimble during cooling if not before.
Sorry, that sounds rather pessimistic, give it a try, they might turn
out beautiful, but be very careful to dry the pebbles out well on top
of the kiln for a week or two, or at least a few firings before you
fire them. quartz pebbles have been known to shatter violently
(explode).
There is a potter in New Zealand who make hand made imitation river
pebbles out of clay - very beautiful.
regards
Steve Harrison
On Friday, August 22, 2003, at 03:54 PM, Joan Berkwitz wrote:
> Here's a goofy question...can beach cobbles be glazed? They look so
> pretty when wet, and dull when dry. It would be fun to glaze them and
> enjoy their subtle colors. The cobbles on our beach are old
> river-tumbled granite, and sometimes quartz, in a wonderful variety of
> colors, with streaks and chunks and spots.
>
> What would happen if they were fired to 06? If no one thinks that they
> would explode or do something terrible, I'll give it a go. And then is
> it just a matter of finding a clear glaze that will fit?
>
> Joanie
>
> _______________________________________________________________________
> _______
> 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.
>
Snail Scott on fri 22 aug 03
At 10:54 PM 8/21/03 -0700, you wrote:
>Here's a goofy question...can beach cobbles be glazed?
>What would happen if they were fired to 06? If no one thinks that they
would explode or do something terrible, I'll give it a go.
It's a strong possibility that they would explode,
with a great deal of force. Not all rocks explode
when fired, but I'd be very leery of just giving
it a try, especially with something as large as a
cobble. Try lacquering them instead.
-Snail
Ann Brink on fri 22 aug 03
Once years ago, I fired 2 black beach rocks from Mexico. They are sold in
bulk at landscape places. (We had them embedded in a cement path) I put
some low fire glaze on them and fired to ^06. They both turned a dark
terra cotta color- they must have been made of compressed clay, whatever
that's called. And, surprise!- one of them opened like a clam- must have
been some expansion going on.
I also tried some obsidian pebbles (apache tears) to 06. Good thing they
were on clay cookies- they foamed up to 10 times their size.
I've put various other small rocks, an inch or so in size, in the kiln,
always protecting the kiln shelf, and often they just change color in some
way. I sometimes think of incorporating rocks into clay in some way,
setting them into a niche that leaves room for shrinkage, with some glaze
for adhering the rock. Another thing to try.....
Good firings,
Ann Brink in Lompoc CA
Christy Pines on fri 22 aug 03
People have been known to polish rocks with nail polish, spray varnish and the like, just to get a shine on them. Wax would probably work as well.
christy
Joan Berkwitz wrote:
>Here's a goofy question...can beach cobbles be glazed? They look so pretty when wet, and dull when dry. It
Zoe Paddy Johnson on fri 22 aug 03
You could get a rock tumbler and use it as intended to polish the rocks,
instead of as a cheapo ball mill the way I do. Smooth, shiny, highly
polished rocks in just 6 weeks! And fun for kids and adults. My mom loved
hers when I was a kid and we spent hours together on camping trips looking
for pretty pebbles to polish. No need to fire, no need for explosions in
the kiln. Pebbles can come apart, vigourously, when heated to only 06.
ZoeJ
Louis Katz on fri 22 aug 03
I recently faked out the geologists with some fake flint nodule.
Actually it was a dark stoneware leather hard chuck that had rolled
around a soldner mixer with some dry porcelain scrap. She identified it
as a flint nodule at a table full of faculty. Lots of fun.
I have successfully fired some slate. I am told that some kinds blow
up, the Indian slate that the Chinese have found a way to export to
Home Despot stores seems to crack but I am going to try a more
controlled firing. A 1ft square is about $2.00 US Treat it as
earthenware. I have glazed it also.
You can heat small pieces of black granite to just under quartz
inversion. The surface oxidizes and becomes red granite. Cutting into
it reveals the black. Possible a very nice effect.
Similarly soapstone carvers occasionally fire soapstone to change its
color, You can probably glaze it too. My only memory was a pretty low
temp. perhaps we took it to cone 022.
Any stone you fire may shatter or blow up more violently than what you
would expect from greenware. Use goggles.
Let us know if you have any success. I have thought about heating
marble to below 1500 degrees F..
Louis
lkatz@falcon.tamucc.edu
Valice Raffi on sun 24 aug 03
Joanie,
I don't know about firing beach cobbles, the saggar suggestion sounded like
a good idea.
I've fired slate alot (no saggar). I used underglazes as washes and also
to paint the designs. Never had any blow up. I didn't try putting a clear
or matt glaze over them tho, preferring the "dry" look.
There used to be an artist on the list, Daryl Schillinberg who fired
river rocks from the Rio Grande. He used Terra Sig on them so they
couldn't have been fired very high. They were/are beautiful - I have one.
I remember him saying he did have occasional blow-ups. I think his kiln
was electric.
Valice
in Sacramento
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