John Baymore on sun 21 sep 97
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Clayart glaze specialists,
There is a beautiful iron saturate cone 10/11 reduction glaze that I
have seen MacKenzie and Hamada put on top of their temokus for an iron red
decoration on the glazed surface of the pot
........ snip.....
I believe you are refering to something called Mashiko Stone. In Japanese
this glaze is called a kaki (pronounced more like kah-key, not kak - key),
which refers to the color of a ripe persimmon. The glaze is called kaki
gusuri.
In Mashiko this glaze is a longtime staple of the village, and is simply a
local stone that is ground up and calcined by the ceramic cooperative
(Kumiai) in town and supplied to the potters in powdered form. The
material is often refered to here as Mashiko Stone. Household kitchen
suribachi (grinding mortars) have been made there bearing this glaze for a
very long time, with the foot of the one above resting on the unglazed
grinding surface of the one below in the kiln.
In Mashiko, a LOT of the gazillion pots you'll see in the shops and studios
there have this glaze somewhere on them=21 Sort of a =22trademark=22 of the
town.
Warren MacKenzie imported a lot of this material for his own use at one
time (may still do it). I got a supply of it many, many years ago (early
70's) when Minnesota Clay was importing it and selling it. I used my
supply sparingly, and mostly as a test to formulate a glaze that looks a
lot like it. Which I have done. After lots of commercial materials tests
I looked to local materials (as I should have to start with) ........ a
local glacial silty clay deposit with 3-4 percent red iron oxide added
gives a good rendition....but still not the same....sigh =3Cg=3E.
Every now and then I mix up a little of the real thing and put it on a
pot.......... it is still really totally unique in color and surface. Have
a bunch of pieces from there with the real thing on them now......... love
to use them. Silky feel.
The rock all by itself is the glaze. Because of this it doesn't stay in
suspention worth a darn. It requires CONSTANT stirring to keep it
suspended. I have added 1percent bentonite to help, but ...........
Simply add 10-20 percent wood ash to the Mashiko kaki stone and you get the
nice rich tenmoku=21
If you have no other formula, a kaki glaze suggested by Herbert Sanders is:
Neph. Syn. 38.7
Colemanite 20.0
Zinc Oxide 8.10
Barium Carb. 9.85
Kaolin 25.8
Flint 33.0
Red Iron Ox. 2 to 6 percent
For me what is particularly infatuating about Mashiko Stone is the surface
quality....... it is a very nice glaze to touch. PArticularly when used
over the clear glaze.. Like a lot of unrefined materials, it offers a
pretty unique color and surface that are very distinctive...... you can
pretty much recognize Mashiko-yaki (pottery) when you see this glaze on a
piece. I and other potters I know have had difficulty really duplicating
it. This situation is very reminiscient (sp?) of true Albany Slip.
Experiment with any American kaki formula over tenmoku. To get the solid
red over the tenmoku the kaki has to go on THICK. Use it at a higher
viscosity than normal dipping consistency, and add a lot of binder to keep
it from flaking off. Easiest on horizontal surfaces (low bowls and plates)
because of this. A slip trailer works well for this for fine lines.
Overpours need to be really thick too, and the pouring tool really
determines the type of marks the pour makes. Experiment with things for
pouring. I use bamboo pouring ladles I have from Japan..... they are
great.
To get fluid glaze pours..... ya gotta have lots of glaze and not worry
about using it up or getting it on the ground. Clear the area well so you
can make broad movements. Start the pour well OFF the piece, get the flow
going and then bring it across the piece. Don't stop until you are well
past the edge of the piece....... follow through like in golf or tennis.
Hamada Shoji often used the kaki over a thin layer of a feldspathic
limestone clear. The clear goes on very thin, then the kaki is put over.
He did this to get a less metallic surface on the kaki and to get more
breaking of the color. (1234 Clear works fine.) If you wax resist over
the clear before the kaki coat, it is really nice. Hamada Shoji often used
the clear areas as the background for later application of overglaze
enamels. The kaki goes black along the wax resist lines where it pulls
back and gets a real thin over the clear (gotta use hot parrafin for
this..... emulsion has never worked for me with this).
Kaki is more of a neutral fire to oxidation glaze to get the best red. I
have experimented with it for many years in my noborigama, and found it
best in the chambers fired neutral or oxidising. If combined with a
tenmoku, reduce early on and then neutral to maturity. If over a
feldspathic clear, after a body reduction period fire slightly oxidising
to maturity. In a wood kiln, if you don't let the coals burn down well
when the chamber is shut down and sealed and have any reduction on the
cooling phase, it goes to a tessha color. Nice..... but not kaki. These
observations were confirmed for me last year when one of the Mashiko
potters whom I visited who uses it a lot (Sado-sensei) shared that comment
with me.
Hope this info is of help. I'm sure you'll get more responses on this one
from some of the other =22old timers=22.
Best,
.....................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore=40Compuserve.com
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