Chrome Red
The glazes discussed here contain 0.2% chrome oxide (Cr2O3).
A correlation between the calcium oxide (CaO) level of a chrome glaze and its red tint
is seen
here:
In these tests, when some of the alkali metals are replaced by
CaO.
The glaze hiCa-chrome-Z2O-1 has higher silica than hiCa-chrome-Z2O-0, and is
glossier.
Low silica version:
inside of bowl:
Outside of bowl:
High silica version:
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
K2O 0.05
Al2O3 0.45
SiO2 2.54
molecular percent Silica 61%
This glaze has .2% Chrome Oxide added
K2O 0.05
Al2O3 0.45
SiO2 3.0
molecular percent Silica 65%
This glaze has .2% Chrome Oxide added
Note that the color saturation is lower in the low silica glaze,
hiCa-chrome-Z2O-0,
These tests are a further indication that high calcium favors the red tint in
glazes containing chrome.
the result is a shift from pink to red.
hiCa-chrome-Z2O-0
bowl is ~3 inches in diameter
hiCa-chrome-Z2O-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 hiCa-chrome-Z2O-0 :
Na2O 0.15
CaO 0.78
MgO 0.02
SnO2 0.14
Empirical Formula glaze hiCa-chrome-Z2O-1 :
Na2O 0.15
CaO 0.78
MgO 0.02
SnO2 0.14
Remarks
though both glazes require a thick application to get a saturated color.