Michael Wendt on wed 28 feb 07
We use Mount St Helens Volcanic ash
that fell on northern Idaho during the
May 18th , 1980 eruption.
It still is a number one seller.
Since it is a loose powder by itself,
I use a dark colored slip clay from
a road cut to bind it. They both fire
the same color pure so I can adjust
glaze fit by changing the proportion
of slip clay from 25-40% of the total.
Fires black in cone 10 oxidation and
a metallic bronze in reduction.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, ID 83501
USA
208-746-3724
http://www.wendtpottery.com
wendtpot@lewiston.com
David Beumee on wed 28 feb 07
Paul wrote,
"> An interesting thing happens when I make a fusion button from the
> rhyolite. It makes a glass with a kind of smokey grey/black color,
> almost exactly like.... obsidian."
My experience is the same. I get volcanic ash, "Navajo Pumice," from CR Minerals Corp. in Santa Fe, available through Laguna as "Pumice FFF," mined from the mind-boggling caldera above Los Alamos NM. A fusion button of this ash, fired to cone 10 in reduction, looks exactly like obsidian.
In an article by Jim Robinson in an issue of Studio Potter dedicated to the use of found materials, Jim gives the following recipe for a ryolitic (volcanic) ash glaze:
58 ryolitic ash
9 silica
33 wood ash
1.5 Veegum T
At cone 10 in reduction, this recipe proved too runny, even with the washed wood ash that I use. I tested the following recipe:
58 ryolitic ash
19 silica
23 wood ash
1.5 Veegum T
This stiffened the melt of the glaze enough to be useful at cone 10. It's a beautiful variegated light blue color over porcelain, definately worth pursuing. Your individual sources of wood ash and volcanic ash will make a huge difference in the outcome, of course.
David Beumee
Porcelain by David Beumee
Lafayette, CO
www.davidbeumee.com
-------------- Original message ----------------------
From: Paul Herman
> Hi Stephani,
>
> I've never tried to use obsidian, but a glass blower friend got a
> wild hair and thought he'd try to blow some. He stuck a chunk in his
> (hot) glass tank pot, and it started to bubble and foam and swell,
> and he just got the stuff out of the door before it got too big. A
> close call, and we speculated about what would have happened if he'd
> been a little slower. I think it has a lot of gasses dissolved in it,
> and when it gets soft they start to bubble out. Perhaps because it
> was cooled under some pressure?
>
> I find little chunks of obsidian in my local rhyolite deposit, when
> digging glaze material. Was the dry lake you mention in N. Nevada way
> up in the NW corner of the state, around Massacre Lake? There's a lot
> of obsidian cobblestones up there. The Paiutes used that area for raw
> material to make points. It's common stuff in volcanic areas.
>
.
>
> Why do I get such a kick out of digging things up and melting them?
>
> Best wishes,
>
> Paul Herman
>
> Great Basin Pottery
> Doyle, California US
> http://greatbasinpottery.com
>
>
> On Feb 26, 2007, at 1:22 PM, stephani stephenson wrote:
>
> > Thinking about obsidian, a naturally occurring glass
> > (r hardness of 5 to 5.5, density 2.6.)
> > rich in silica, and usually iron and some manganese
> > too....
> >
> > is ground or crushed obsidian ever used in formulation
> > of glazes or as an additive to a clay body?
> >
> > i'm wondering if it would melt easier than it's
> > relatives: granite or rhyolite, because it is already
> > in a glassy state ( i.e. like ground frit )
> >
> > have no idea if this would be true and i wonder if
> > anyone has heard of it's use?
> >
> > or perhaps it occcurs too rarely or is too problematic
> > to be feasible
> > for industry...
> >
> > I remember an alkaline lake bed in N.Nevada, strewn
> > with what looked like white pebbles. the pebbles and
> > rocks turned out to be black obsidian, with a white
> > alkaline crust...and of course the beautiful Glass
> > buttes in oregon. Though of course , you leave the
> > obsidian in place when you visit...
> >
> > never seen reference to it in ceramics...
> > just curious
> >
> > Stephani Stephenson
> >
> >
> >
> >
> > ______________________________________________________________________
> > ______________
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> >
> > ______________________________________________________________________
> > ________
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> >
> >
>
> ______________________________________________________________________________
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Hank Murrow on wed 28 feb 07
>
I mine a Rhyolitic ash from Williams Lake in British Columbia. When 10%
Talc and 10% Wollastonite are added to it, it mecomes a lovely pale
blue celadon resembling the Song originals.
Cheers, Hank
www.murrow.biz/hank
Edouard Bastarache Inc. on wed 28 feb 07
Hello Hank,
at what temp do you fire this mixture.
Later,
Edouard Bastarache
Le Français Volant
The Flying Frenchman
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
www.thepottersshop.blogspot.com
http://www.ceramique.com/cerambooks/rayons/technologie.php
http://www.flickr.com/photos/30058682@N00/
Paul Herman on wed 28 feb 07
David, and Hank,
My rhyolite comes from the roadcut by my mailbox. It makes a glaze
pretty much by itself, but I use the mix:
roadcut 45
feldspar 45
halloysite clay 10
This glaze is what I call a shino, best in the wood with some iron
painting underneath. It's been selling, so I'm making more for firing
in early April. A month of very hard work staring me in the face.
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Feb 28, 2007, at 7:54 AM, David Beumee wrote:
> My experience is the same. I get volcanic ash, "Navajo Pumice,"
> from CR Minerals Corp. in Santa Fe, available through Laguna as
> "Pumice FFF," mined from the mind-boggling caldera above Los Alamos
> NM. A fusion button of this ash, fired to cone 10 in reduction,
> looks exactly like obsidian.
>
Mike on thu 1 mar 07
Dude,
You're getting me all hot and bothered here with your glaze description,
how about some pics to satisfy us jaded folk? I searched your website
but didn't see this particular glaze mentioned. Is it on any of the
pieces in your gallery?
Mike
Mike
in Taku, Japan
karatsupots.blogspot.com
potteryofjapan.com
Paul Herman wrote:
> David, and Hank,
>
> My rhyolite comes from the roadcut by my mailbox. It makes a glaze
> pretty much by itself, but I use the mix:
>
> roadcut 45
>
> feldspar 45
>
> halloysite clay 10
>
> This glaze is what I call a shino, best in the wood with some iron
> painting underneath. It's been selling, so I'm making more for firing
> in early April. A month of very hard work staring me in the face.
>
> Paul Herman
>
> Great Basin Pottery
> Doyle, California US
> http://greatbasinpottery.com
>
>
> On Feb 28, 2007, at 7:54 AM, David Beumee wrote:
>
>> My experience is the same. I get volcanic ash, "Navajo Pumice,"
>> from CR Minerals Corp. in Santa Fe, available through Laguna as
>> "Pumice FFF," mined from the mind-boggling caldera above Los Alamos
>> NM. A fusion button of this ash, fired to cone 10 in reduction,
>> looks exactly like obsidian.
>>
>
> ______________________________________________________________________________
>
> 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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