Shifting Edges
A relative of the glaze seen
here .
The glaze shown in this note, iron_Alex_0_Z38, has the same silica and alumina
as iron_Alex_0PSiMAlk,
Both iron_Alex_0_Z38 and iron_Alex_0PSiMAlk feature a glossy matrix with a
variety of distinct crystals.
The matrix of iron_Alex_0_Z38 is variegated, showing a translucent swirled
burgundy near the rim, varying
The nature of the crystals varies equally as that of the matrix. Both glazes
have near circular
The most prominent crystals in iron_Alex_0PSiMAlk are the acicular crystals
some of which are densely
The crystal dust in iron_Alex_0PSiMAlk is predominantly dots of
microcrystalline iron red.
To sum up, iron_Alex_0_Z38 has fewer crystals, with greater variety, in a more
richly variegated glassy matrix.
Note that the acicular crystals in both glazes show variations in color
resulting from absorbing
Pictures of the glaze iron_Alex_0_Z38, and close-ups of several
of its features, are shown.
bowl is ~ 3.5 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 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 0.09
Al2O3 0.57
SiO2 3.33
molecular percent Silica 65%
K2O 0.07
Al2O3 0.57
SiO2 3.31
molecular percent Silica 65%
Each crystal that can grow in a glaze, has the environment in which it grows
most readily.
I do not see those coppery metallic crystals in low alkali metal glazes.
In this case the higher alkali metal
Matte microcrystals seem more prevalent in lower alkali metal glazes, and
these are seen in iron_Alex_0PSiMAlk.
but it has less MgO and more alkali metals in its
empirical formula.
The forms of the micro-crystals in the two
glazes are related though not identical.
to an opaque orangey brick red, and green
confection. In omparison, iron_Alex_0PSiMAlk has a near uniform
brown black
glossy matrix.
crystal clusters, acicular crystals, and crystal
'dust', i.e. itsy particle clusters showing no morphological
distinctions, but the crystal surface coverage of Iron_Alex_0PSiMAlk is
substantially greater in
iron_Alex_0_Z38.
packed into a distorted hexagonal lattice. The
only crystals in iron_Alex_0_Z38 that densely cover a region,
are the
coppery colored metallic crystals, which are almost absent from
iron_Alex_0PSiMAlk.
while in iron_Alex_0_Z38, this 'dust' is
coppery colored metallic particles.
Its near neighbor glaze iron_Alex_0PSiMAlk
has a surface dominated by a latticework of massed acicular crystals,
with a
dusting of red micro-crystals.
various oxides from the glaze.
Image of the glaze iron_Alex_0_Z38
inside
outside
Close up images of glaze texture
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 iron_Alex_0_Z38 :
Na2O 0.42
Li2O 0.15
CaO 0.32
MgO 0.02
Fe2O3 0.16
P2O5 0.03
Empirical Formula iron_Alex_0PSiMAlk :
Na2O 0.33
Li2O 0.15
CaO 0.33
MgO 0.12
Fe2O3 0.16
P2O5 0.04
Remarks
content of iron_Alex_0_Z38 promotes
larger individual crystals, and also the coppery metallic crystals.