Snowflake
Rutile Crystals
These two glazes show rutile crystals on a blue-grey background, the first
glaze, hiAlk_Z3P_Z3Q has small
In these two glazes, alumina, as well as the silica:alumina ratio are similar,
though not equal. hiAlk_Z3P_Z3Q has
These glazes are sufficiently different in composition to suggest that rutile
crystals can appear in a range of glaze
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 1850 deg F then a two hour hold at 1850 deg F
300 deg F an hour to 1750 deg F then a one 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 0.13
Al2O3 0.65
SiO2 3.63
molecular percent Silica 65.62%
K2O 0.12
Al2O3 0.60
SiO2 3.28
molecular percent Silica 63.43%
circular clusters of rutile crystals,
which I characterize as 'snowflakes'. The second glaze, hiAlk_Z3P_MAl, has
in
addition to a small number of snowflakes, a large number of amorphous
irregularly shaped regions,
pale grey on the inside, edged in white.
Perhaps these are 'melting' snowflakes.
higher silica and alumina, so
proportionately less base. It also has less alkali metals because it has
higher
MgO and correspondingly lower Na2O than hiAlk_Z3P_MAl.
compositions. Yet I have seen them
only in glazes with alumina greater than 0.6, silica:alumina ratio below 6,
and
alkali metal:alumina ratio > 0.7.
Image of the glaze hiAlk_Z3P_Z3Q
inside
outside
Image of the glaze hiAlk_Z3P_MAl
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 hiAlk_Z3P_Z3Q :
Na2O 0.42
CaO 0.35
MgO 0.1
P2O5 0.06
TiO2 0.19
Empirical Formula hiAlk_Z3P_MAl:
Na2O 0.51
CaO 0.35
MgO 0.02
P2O5 0.06
TiO2 0.22