Veena Raghavan on tue 5 jan 99
I request to our many glaze experts. When a glaze calls for Volcanic Ash,
is this a special Volcanic Ash or is it the same as pummice. Sorry if this
is a very basic question, but I can't seem to find the answer in any of the
books I have. If Volcanic Ash cannot be substituted with pummice, where can
obtain the Volcanic Ash.
Thank you in advance for your help and tolerance!
Veena
Veena Raghavan
75124.2520@compuserve.com
Paul Lewing on wed 6 jan 99
Veena Raghavan wrote:
>
> ----------------------------Original message----------------------------
> I request to our many glaze experts. When a glaze calls for Volcanic Ash,
> is this a special Volcanic Ash or is it the same as pummice. Sorry if this
> is a very basic question, but I can't seem to find the answer in any of the
> books I have. If Volcanic Ash cannot be substituted with pummice, where can
> obtain the Volcanic Ash.
Hi, Veena,
There is no single formula for volcanic ash, or for pumice, because
the composition of anything that a volcano puts out depends on the
composition of the particular stuff under that volcano. Volcanic ash
has been thrown up into the air and usually air-floated a ways so it's
pretty consistent for particle size. Pumice is spewed out onto the
ground, with lots of gas in it. If it were more solid, you'd call it
lava.
Most of the volcanic ash that you can buy from ceramic suppliers in
the US comes from that gigantic caldera in New Mexico north of Santa
Fe, which covered most of the Midwest with ash. In Europe, I think
it's mostly from Mt. Etna in Sicily. These are pretty consistent in
formula, but different from each other, and you can find the formula
in books. It is also possible to find Mt. St. Helens ash, and if you
need a formula for it, I can send you one.
I wouldn't think you could substitute pumice for ash, although you
might get an interesting result. My methodology is to always give it
a try.
Paul Lewing, Seattle.
Almost recovered from my foot injury enough to go back to racquetball.
I can hardly wait.
Thonas C. Curran on thu 7 jan 99
Reading the postings on volcanic ash reminded me that I've got a small
batch of experimental glaze w/ VA in it, and it's like cement when I try
to stir it up. I added epsom salts to the original batch, and even a
sharp knife doesn't seem to help break up the glaze to make it useable
again. It's much worse than any glaze with a lot of frit in it...TIA if
you can shed any light on this. I haven't happened to see anything on
the subject, but I've not been looking. Clayart so often comes in handy
for questions which have no priority to speak of when time is pressing.
Carolyn aka CNC
John Jensen on thu 7 jan 99
I got hold of some volcanic ash from the eruption at Monserat last year and
substituted it in my "white breaking brown recipe" which is about 65% ash
and 35% Gerstley borate with some 3.5% tin and 3.5% opax. The Monserat ash
gave a similar glaze but with a yellow color and more visual texture.
John Jensen, Mudbug Pottery, Annapolis, Md.
Vince Pitelka on thu 7 jan 99
>composition of the particular stuff under that volcano. Volcanic ash
>has been thrown up into the air and usually air-floated a ways so it's
>pretty consistent for particle size. Pumice is spewed out onto the
>ground, with lots of gas in it. If it were more solid, you'd call it
>lava.
I believe that pumice is just the large chunks of volcanic ash which settle
directly around the vent to form a cinder cone. Any lava which flows from
the volcano is far denser than pumice. As I understand it, pumice and
volcanic ash are interchangeable in glazes. Ground pumice should be
identical to the ash which falls farther from the volcano.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Veena Raghavan on fri 8 jan 99
John,
Thanks for your posting about Volcanic Ash. Is the Montserrat
available from anywhere, or were you just lucky to get it. I had a
son-in-law temporarily posted to a place near a semi-active volcano in
Indonesia for a year but, unfortunately, at that time I was not trying to
mix glazes and had no thought of asking him to try and get me some! What an
opportunity lost!!
Also, if you would not mind, did you fire this to Cone 6 or higher.
The studio where I do my work only fires to Cone 6.
Thanks again and all the best
Veena
Eric Hansen on sat 9 jan 99
Hi
Reportedly we have large amounts of volcanic ash in the western part of Kansas h
Eric Hansen, Lawrence, Kansas
--
On Thu, 7 Jan 1999 09:39:39 Vince Pitelka wrote:
>----------------------------Original message----------------------------
>>composition of the particular stuff under that volcano. Volcanic ash
>>has been thrown up into the air and usually air-floated a ways so it's
>>pretty consistent for particle size. Pumice is spewed out onto the
>>ground, with lots of gas in it. If it were more solid, you'd call it
>>lava.
>
>I believe that pumice is just the large chunks of volcanic ash which settle
>directly around the vent to form a cinder cone. Any lava which flows from
>the volcano is far denser than pumice. As I understand it, pumice and
>volcanic ash are interchangeable in glazes. Ground pumice should be
>identical to the ash which falls farther from the volcano.
>- Vince
>
>Vince Pitelka - vpitelka@DeKalb.net
>Home 615/597-5376, work 615/597-6801, fax 615/597-6803
>Appalachian Center for Crafts
>Tennessee Technological University
>1560 Craft Center Drive, Smithville TN 37166
>
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Tony Hansen on sat 9 jan 99
> When a glaze calls for Volcanic ash, is this a special volcanic
> ash or is it the same as pumice
Ash glazes travel very poorly. Ash cries out "formulate a glaze especially
for me, I am like no other!" Volcanic ash chemistries vary greatly.
The best approach is to make a committment and get a good supply. Then get
a chemical formula so you can determine in what way the ash formula
differs from a middle-of-the-road limit formula for the type of glaze
you want. Then use a calculation program to derive a recipe. Chances are
the ash has lots of silica and not enough alumina.
We have a 10 inch seam of ash in one of our clay quarries. I can get
a good bamboo glaze using 60 ash, 20 dolomite and 20 kaolin. Ball milling
really benefits it.
----
T o n y H a n s e n thansen@digitalfire.com
Don't fight the dragon alone http://digitalfire.com
Calculation/Database Software for Ceramic Industry
Joy Holdread on sat 9 jan 99
In a message dated 1/7/99 7:51:23 AM US Mountain Standard Time,
mudbug@toad.net writes:
> ---------------------------Original message----------------------------
> I got hold of some volcanic ash from the eruption at Monserat last year and
> substituted it in my "white breaking brown recipe" which is about 65% ash
> and 35% Gerstley borate with some 3.5% tin and 3.5% opax. The Monserat ash
> gave a similar glaze but with a yellow color and more visual texture.
>
> John Jensen, Mudbug Pottery, Annapolis, Md.
>
Was the original recipe for wood ash glaze or VA? And What cone?
Joy in Tucson
John Jensen on wed 13 jan 99
Original recipe is with Volcanic ash...Cone six. A shiney glaze which is
white where thick and brown where thin. Breaks brown on edges.
John Jensen, Mudbug Pottery, Annapolis. Md.
>>
>Was the original recipe for wood ash glaze or VA? And What cone?
>Joy in Tucson
>
>
John Jensen, mudbug@toad.net
Mudbug Pottery
Annapolis, Md.
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