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terra sig and mica

updated mon 31 jul 06


Patricia Gilmartin on wed 26 jul 06

Has anyone tried adding mica or other powdered metal to terra sig to try =
to get a little depth or sparkle to the clay surface?

Snail Scott on thu 27 jul 06

At 06:41 PM 7/26/2006 -0400, you wrote:
>Has anyone tried adding mica or other powdered metal to terra sig to try
to get a little depth or sparkle to the clay surface?

Particles large enough to provide visible sparkle
tend to interfere with the burnishing, and make
a slightly lumpy surface. It does basically work,
at least with mica. Don't know about metal,
though; might oxidize and get dull/rusty/black,
depending on the metal in question, but probably
not stay shiny.


John Guerin on thu 27 jul 06

Hi Patricia,

An easier way to add the mica sparkle to the clay surface is to sprinkle the
dry mica on the newly burnished surface and immediatly burnish it into the
surface. If you do this at the 'leather hard' stage, the mica is pushed
into the clay and leaves a very smooth finish.

John Guerin
Tucson, AZ

----- Original Message -----
From: "Patricia Gilmartin"
Sent: Wednesday, July 26, 2006 3:41 PM
Subject: terra sig and mica

Has anyone tried adding mica or other powdered metal to terra sig to try to
get a little depth or sparkle to the clay surface?

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Bonnie Staffel on fri 28 jul 06

Dear Snail,

When I first started to do simple pit firing, more on the surface of the
ground rather than deep inside, while the clay was still soft leather hard,
I applied mica to the surface and being "platelets" in form, it sure did
some fancy shining, although the whole piece came out gray. I should try
some more now that I know more about how to do this type of firing.


Bonnie Staffel

Snail Scott on sat 29 jul 06

At 11:12 PM 7/28/2006 -0400, Bonnie S wrote:
>Dear Snail,
>When I first started to do simple pit firing...
>I applied mica to the surface and being "platelets" in form...the whole
piece came out gray...

I have mainly seen mica used in traditional
Jicarilla Apache pottery. The mica is naturally
present in the local clay, so it goes all the
way through. Not usually burnished, just smoothed.
The clay is orange, and the mica turns golden-
yellow. Lots of it - very sparkly. It is VERY
low-fired; just hot enough to burn off the carbon
from the flames. The very low vitrification
combines with the mica to make functional ware
with very high thermal-shock resistance. It is
often fired in open flame with no saggar or kiln.
Such pottery is widely used locally as stovetop
bean pots.

Felipe Ortega is the biggest 'name' in this
style, and was selling to Bloomingdale's in New
York for a while. (Bet those New Yorkers didn't
use them to cook their beans...)

I have seen mica from other places which didn't
look as nice, so I suspect that all mica is not
created equal.

New Mexico Clay used to manufacture several
colored clay bodies with a high mica content,
though I don't know if it's high enough to allow
for an unsaggared open firing. I'm also not
sure what the cone-equivalent would be, but I
suspect the traditional stuff I've seen is fired
down around the ^020 range. (Brent? any comment?)
Also, Coyote Clay makes micaceous engobes for
coating conventional clays, for that Jicarilla-
style look.

Allyson May on sun 30 jul 06

Seattle Pottery Supply used to sell a micaceous clay body. It was =
orange red in color similar to red art. I have used it for hand =
building vessels which were then burnished and pit fired (barrel =
method). The clay body its self was burnished without a problem. The =
mica was very visible after firing, looking like gold glitter sprinkled =
over the pieces. I also have a beautiful pueblo piece by Lind =
Tafoya-Qyenque from Santa Clara which is black ware. Most of the piece =
is burnished but some of the carving which is matt has been painted with =
micaceous slip. The mica is visibly shiny but black. Very nice =
Allyson May
Stoney Creek Pottery
Bloomington, IN