Nickel Colors
This glaze has a micro-crystalline surface layer in a transparent matrix. It
contains barium oxide and zinc oxide.
This glaze is derived by a circuitous route from the glaze number 404 in
Emmanuel Cooper book
inside of bowl:
Outside of bowl:
150 deg F an hour to 250 deg F
400 deg F an hour to 1800 deg F
300 deg F an hour to 2050 deg F
120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F
300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F
300 deg F an hour to 1700 deg F then a Three hour hold at 1700 deg F
25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F
This glaze has 1.5% Nickel Oxide added
K2O 0.11
Al2O3 0.35
SiO2 2.23
molecular percent Silica 62%
The spirit of the original cooper glaze is low alkali metals; this glaze has
alkali metals 0.13 essentially the same as the 0.12 of the original
Most of the BaO in the original glaze is replaced by ZnO, and alumina and
silica are significantly higher.
This glaze is separated into two distinct phases, a microcrystalline phase
which is prominent where the glaze is thickly applied,
The nickel oxide colors the microcrystalline glaze an intense aqua, and the
matrix brown.
Note that this glaze has minimal CaO, only that CaO and MgO which are present
in all clays and feldspars.
The brown matrix shows that nickel oxide can color a glaze brown even if the
glaze is low in CaO.
The microcrystalline phase is a deap
aqua as a result of the addition of nickel oxide. The glossy matrix is
brown.
"The Potters Book of Glaze Recipes".
cooper_404_Z2F_1
bowl is ~3 inches in diameter
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile
Down Fire Profile
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula glaze cooper_404_Z2F_1 :
Na2O 0.02
CaO 0.01
MgO 0.01
BaO 0.22
ZnO 0.63
Remarks
Cooper glaze.
and a full gloss
transparent matrix which peeks out where the glaze is thin.
Previous work on glazes colored with nickel oxide
has convinced me that CaO promotes gray and brown colors.