Steve Mills on wed 10 sep 08
Unlikely, Cornish (Cornwall) Stone is a form of Feldspar with no dominant colour.
I use pure Basalt obtained locally, on a white body that's almost black.
Steve
Bath
UK
--- On Wed, 9/10/08, Dave Pike wrote:
From: Dave Pike
Subject: Re: Cornwall Stone - Rocks - percentage moisture
To: CLAYART@LSV.CERAMICS.ORG
Date: Wednesday, September 10, 2008, 5:51 AM
Hello,
I use a glaze here called kimachi. It is a black glaze made from a
single material, a type of stone. I have heard an equivalent is Cornwall
stone. Does anyone know if that is actually the case?
Thanks,
Dave
http://togeii.wordpress.com/
Neon-Cat on thu 11 sep 08
Hi Dave and all!
Kimachi Stone, also called Kimachi Sandstone or Kimachi-ishi Stone is a
clay-bearing, clastic sedimentary rock composed of andesite, chlorite,
tri-octahedral Fe smectite (montmorillonite), and zeolite (with possibly
other constituents). Kimachi stone is found at the southern coast of Shinji
Lake, Shimane, Japan, and is a bluish-gray to brownish, homogeneous, soft,
medium-grained tuffaceous sandstone of the Miocene Omori Formation. It has
been quarried for processing into various household utensils, pavers, Izumo
stone lanterns, and art forms since the Japanese Burial Mound Period (circa
300-710). Today commercial stone is selectively colored in shades of red,
reddish-brown, brown, dark-brown, and black. Natural stone weathers,
becoming darker as the iron it contains oxidizes.
Kimachi Stone (in general):
SiO2 - 65.77
TiO2 - 0.59
Al2O3 - 17.68
FeO - 5.65
MgO - 1.80
CaO - 5.10
Na2O - 2.27
K2O - 1.12
Total - 99.98
Density 1.98 - 2.54 g/cm3
Porosity 16.54 - 24 percent
Water content 9 percent
Cornwall Stone (Cornish Stone) is also a rock with the general composition
of quartz, soda and potash feldspar, mica (muscovite), kaolinite, and
amorphous silica (usually as opal).
Cornwall Stone (in general):
SiO2 - 73.00
TiO2 - 0.10
Al2O3 - 16.50
Fe2O3 - 0.14
MgO - 0.15
CaO - 2.05
Na2O - 3.70
K2O - 3.70
P2O5 - 0.10
Total - 99.44
Rocks are mixtures of one or more minerals. Feldspars are minerals. Kimachi
Sandstone and Cornwall Stone are neither feldspars nor minerals. They're
both, as rocks, a combination of minerals that can be separated into their
respective constituents. In ceramics, keeping their general composition in
mind, we use both like we do the feldspars.
I did some recent experiments using 90 percent Cornwall Stone, 10 percent
Whiting and 0.50 iron oxide that made for a nice, simple, light, clear Cone
10 reduction glaze. Everyone liked the glaze so yesterday I made up a
5000-gram batch of a plain version (sans iron) for everyone to use or try.
I'll see about putting some tests into the kiln on Monday using colorants
for black. If you fire Cone 6, this Cornwall Stone glaze probably won't
work.
Hope this helps, Dave.
Happy Thursday everyone!
Marian
Neon-Cat Ceramics
--- On Wed, 9/10/08, Dave Pike wrote:
Hello,
I use a glaze here called kimachi. It is a black glaze made from a
single material, a type of stone. I have heard an equivalent is Cornwall
stone. Does anyone know if that is actually the case?
Thanks,
Dave
http://togeii.wordpress.com/
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