Iron Yellow surface micro-crystals
Iron-Yellow surface micro-crystals emerge on a contrasting matrix glaze with
the two glazes
The difference in composition between these two glazes is only in silica and
alumina and the silica:alumina ratio.
bowl is ~ 4 inches in diameter.
bowl is ~ 3 inches in diameter
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 4 hr hold at 1750 deg F
25 deg F an hour to 1650 deg F then a 1 hr hold at 1650 deg F
K2O 0.15
Al2O3 0.54
SiO2 3.30
molecular percent Silica 64.1%
K2O 0.15
Al2O3 0.45
SiO2 4.00
molecular percent Silica 69.5%
wisskirchen-Halloween-M and wisskirchen-Halloween-Mod. In
the glaze wisskirchen-Halloween-M, the matrix
glaze is a yellowish brown
microcrystalline matte, and the iron-yellow microcrystals take the form of
a
dusting of matte particles with colors ranging from pale yellow through
chartreuse. By contrast
the micro-crystals in wisskirchen-Halloween-Mod
are glossy opaque yellow, sharply demarcated from the
glossy black
matrix.
Wisskirchen-Halloween-Mod has
lower alumina, and higher silica with a substantially higher silica:alumina
ratio
as a result. The two glazes have nearly the same bases in the first
column of their respective Empirical Formula.
Image of the lower silica:alumina glaze wisskirchen-Halloween-M
inside
outside
Image of the higher silica:alumina glaze wisskirchen-Halloween-Mod
inside
outside
oxidation firing to cone 10 in an electric kiln
Firing profile
Up Fire profile cone 10
Down Fire Profile cone 10
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Lower Silica:Alumina Glaze:
Empirical Formula wisskirchen-Halloween-M:
Na2O 0.05
CaO 0.61
MgO 0.19
Fe2O3 0.25
TiO2 0.05
Higher Silica:Alumina Glaze:
Empirical Formula wisskirchen-Halloween-Mod
Na2O 0.05
CaO 0.60
MgO 0.20
Fe2O3 0.24
TiO2 0.06