iglasgo on wed 29 mar 06
Over the past few months I've corresponded with Nathan and a few other
Clayarters about native clays. There is a lovely blue-green volcanic
ash readily available around here, which I've been testing as a clay &
maybe as a glaze. I finally glaze fired yesterday, so now I have some
results to talk about.
First, the clay. The blue-green ash comes out of the roadcut as a
super fine, dry powder with small chunks of easily crushed powdery
claystone. It appears not to have any organic content. I didn't screen
or sieve it at all. It hydrates nicely to a smooth, squishy feeling
clay, with a good "clay" smell. It is somewhat workable for
handbuilding but definitely quite short. I haven't tried it on the
wheel yet. When the clay dries, it is the hardest greenware I've ever
seen. It takes a burnish very nicely. I mixed some of it 50-50 with a
white stoneware, and it seems well behaved and much more plastic. So
far, so good.
Firing 1 was a ^04 bisque firing. Regrettably, I did not photograph
the results. The native clay fired to a rich iron red, like a brick,
but smoother. Appeared to be slightly vitrified. The burnished areas
were very nice and shiny, and the fired ware was very strong, compared
to the ^6 stoneware. The 50-50 mix fired to a lighter iron red. The
50-50 mix was inlaid into white stoneware tiles, and seemed to have
about the same COE as the tiles, it did not pull away from the edges.
So far, so good.
Firing 2 was a ^6 glaze firing. I've posted photos at
http://www.flickr.com/photos/ivyg/. The 100% native clay melted into a
dark, ominous foamy puddle, and cracked the bowl that it was sitting
in. The 50-50 mix fired to a warm grey-brown color with dark specks.
Very pretty, and it looks like it will take glaze well. Native clay
chunks mixed into clear glaze fired as dark iron brown spots with a
hint of green along their edges. The native clay caused the glaze to
crawl.
I also dug up some white volcanic ash to test. It's texture is far too
sandy for use as a clay. It is very loose and powdery, with no visible
organic material. Applied to a pot at 100%, it fires to a very nice
root beer gloss at ^6. Mixed 25% into white stoneware, it makes a
flaky, abrasive, light sand colored slip. Clear glaze applied to both
of these crawled like crazy.
All in all, I'm pleased with the results, and I can't wait to find a
place to go dig up a ton of the blue-green stuff. There's lots of
other native clays around here too, and I am chomping at the bit to
test all of them. There's a rich red, an ocher yellow, and some
gray-whites... who knows what they will yield!
-Ivy G.
Hank Murrow on wed 29 mar 06
On Mar 28, 2006, at 4:50 PM, iglasgo wrote:
> There is a lovely blue-green volcanic
> ash readily available around here, which I've been testing as a clay &
> maybe as a glaze. I finally glaze fired yesterday, so now I have some
> results to talk about.
> Firing 1 was a ^04 bisque firing. The native clay fired to a rich iron=20=
> red, like a brick, but smoother. Appeared to be slightly vitrified.=20
> The burnished areas were very nice and shiny, and the fired ware was=20=
> very strong,
dear Ivy;
Use that blue green stuff for making things, and glaze it with itself=20
and some flux (maybe a frit). You will need to do a line blend to=20
determine how much flux to add. Voil=E0! Ware.
Also, talk to well drillers in your area, as they know a lot about what=20=
lies under the surface.
]
Cheers, Hank
www.murrow.biz/hank
Ann Brink on wed 29 mar 06
Ivy, thanks for posting all this-very interesting to see your photos of your
tests. I have been experimenting with some white volcanic ash from a roadcut
near Alturas CA and have very similiar results. I have added small amounts
of the coarser grained material to get what I call a "freckle" glaze (I used
it on thrown eggs). Looks just like my grandson's nose-soft freckles (cone
7 ox). Also I've sprinkled it in dry form on freshly thrown white stoneware
pots with interesting results...a dark shiny beaded effect. I bet in a
reduction firing they would look like David Hendley's hoof cups on his
website.
Ann Brink in Lompoc CA
Ivy wrote: "I also dug up some white volcanic ash to test. It's texture is
far too
sandy for use as a clay. It is very loose and powdery, with no visible
organic material. Applied to a pot at 100%, it fires to a very nice
root beer gloss at ^6. Mixed 25% into white stoneware, it makes a
flaky, abrasive, light sand colored slip. Clear glaze applied to both
of these crawled like crazy.
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