Crossing lines
Several small changes are a big change.
A glaze covered in abutting acicular micro-crystals, acicular_P_iron, is
transformed into
The first glaze is a micro-crystalline matte; the second is a dark
textured gloss glaze with a variety of
The crystals are larger, have a metallic
glitter, and the rays from center
A line is crossed. These two dissimilar glazes have nearly equal
alumina, silica, total alkali metals,
Is the difference in the Calcium:Magnesium balance between these two glazes
sufficient to account
bowl is ~ 4 inches in diameter.
bowl is ~ 4 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 50 min hold at 1750 deg F
50 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 0.08
Al2O3 0.62
SiO2 3.3
molecular percent Silica 65.4%
K2O 0.09
Al2O3 0.59
SiO2 3.3
molecular percent Silica 65.1%
acicular_P_iron_3_1; a glaze containing a variety of
crystals in a variegated glossy matrix.
crystals which include some coppery
colored acicular crystals. These acicular crystals dominate this glaze
if it
is applied thickly, as is seen in the bottom of the bowl.
to edge are clearly defined, as they are
not in the first glaze, Additionally, the dusting of teensy red
crystals
in the second glaze is not present in the first. The second glaze is
more varied.
and total alkaline earths. There
are only small differences in the other oxides in their empirical formulae
except that the first has slightly higher Magnesium, and correspondingly
lower Calcium. These glazes
are in distinct glaze families; the
composition of the phases in these two glazes are different.
for the difference in appearance? This will be tested.
Image of the glaze acicular_P_iron
inside
outside
Image of the glaze acicular_P_iron_3_1
inside
outside
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 acicular_P_iron :
Na2O 0.38
Li2O 0.15
CaO 0.28
MgO 0.11
Fe2O3 0.12
P2O5 0.03
Empirical Formula acicular_P_iron_3_1 :
Na2O 0.40
Li2O 0.15
CaO 0.32
MgO 0.04
Fe2O3 0.14
P2O5 0.03