Several Glazes with Similar UMF
Here are several glazes with nearly the same UMF, sourced from different
materials, the differences
What I've been refering to as the Empirical Formula is commonly called the UMF.
The design is created by adhering a mask and then applying the main
glaze. After drying,
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 1550 deg F then a 1 hr hold at 1550 deg F
300 deg F an hour to 1650 deg F then a 1 hr hold at 1650 deg F
400 deg F an hour to 1750 deg F then a 2 hr hold at 1750 deg F
400 deg F an hour to 1900 deg F then a 3 hr hold at 1900 deg F
K2O 0.16
Al2O3 0.52
SiO2 3.20
molecular percent Silica 67.8%
Added:
2.5% Cobalt Carbonate
K2O 0.15
Al2O3 0.52
SiO2 3.20
molecular percent Silica 67.7%
Added:
2.5% Cobalt Carbonate
K2O 0.15
Al2O3 0.52
SiO2 3.26
molecular percent Silica 68.1%
Added:
2.5% Cobalt Carbonate
K2O 0.15
Al2O3 0.52
SiO2 3.24
molecular percent Silica 67.9%
Added:
2.5% Cobalt Carbonate
K2O 0.15
Al2O3 0.52
SiO2 3.23
molecular percent Silica 67.7%
Added:
2.5% Cobalt Carbonate
K2O 0.18
Al2O3 0.64
SiO2 3.54
molecular percent Silica 64.9%
The recipes all add to 200, so quantities of individual components can be
compared.
I note that the last three glazes zincSr_Z3T_PZn_PSi_1, zincSr_Z3T_PZn_PSi_2,
zincSr_Z3T_PZn_PSi_3,
These glazes are characterized by micro-crystalline surface crystals growing
out of an underlying
The three glazes zincSr_Z3T_PZn_PSi_1, zincSr_Z3T_PZn_PSi_2,
zincSr_Z3T_PZn_PSi_3 show
Perhaps the silica in the frit is more easily accessible to the glaze than
that of the feldspar in
Ball Clay contains contaminants that likely are not reported in the analysis,
and available
in result are large.
the mask is removed and the open area filled in with a
second glaze, using a bulb syringe
with a needle applicator.
Image of the glaze zincSr_Z3T_PZn_PSi
Image of the glaze zincSr_Z3T_PZn_PSi_0
Image of the glaze zincSr_Z3T_PZn_PSi_1
Image of the glaze zincSr_Z3T_PZn_PSi_2
Image of the glaze zincSr_Z3T_PZn_PSi_3
the third and fourth images are plates ~6 inches in diameter, the others
are bowls ~6 inches in diameter.
oxidation firing to cone 10 in an electric kiln
Firing profile - Invert Firing
Up Fire profile cone 10
Down Fire Profile cone 10
Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.
glaze composition
Empirical Formula zincSr_Z3T_PZn_PSi:
Na2O 0.31
CaO 0.02
MgO 0.17
SrO 0.15
ZnO 0.19
Recipe zincSr_Z3T_PZn_PSi:
Bentonite
6
EPK_Kaolin
10
Frit_413
18
G_200_EU_Feldspar
50
Magnesium_Carbonate
8
Nepheline_Syenite
72
Silica
14
Strontium_Carbonate
13
Zinc_Oxide
9
cobalt carbonate
5
Empirical Formula zincSr_Z3T_PZn_PSi_0:
Na2O 0.31
CaO 0.03
MgO 0.17
SrO 0.16
ZnO 0.18
Recipe zincSr_Z3T_PZn_PSi_0:
Bentonite
6
G_200 EU Feldspar
30
Magnesium Carbonate
8
Nepheline Syenite
109
Silica
24
Strontium Carbonate
14
Zinc Oxide
9
cobalt carbonate
5
Empirical Formula zincSr_Z3T_PZn_PSi_1:
Na2O 0.31
CaO 0.04
MgO 0.14
SrO 0.15
ZnO 0.21
Recipe zincSr_Z3T_PZn_PSi_1:
Custer Feldspar
74
EPK Kaolin
32
Frit 413
43
Nepheline Syenite
18
Strontium Carbonate
13
Talc
10
Zinc Oxide
10
cobalt carbonate
5
Empirical Formula zincSr_Z3T_PZn_PSi_2:
Na2O 0.32
CaO 0.01
MgO 0.18
SrO 0.15
ZnO 0.19
Recipe zincSr_Z3T_PZn_PSi_2:
Custer Feldspar
80
EPK Kaolin
38
Frit 413
52
Magnesium Carbonate
8
Strontium Carbonate
13
Zinc Oxide
9
cobalt carbonate
5
Empirical Formula zincSr_Z3T_PZn_PSi_3:
Na2O 0.32
CaO 0.02
MgO 0.18
SrO 0.14
ZnO 0.19
Recipe zincSr_Z3T_PZn_PSi_3:
Ball Clay
40
Frit 413
40
G_200 EU Feldspar
59
Magnesium Carbonate
8
Nepheline Syenite
32
Strontium Carbonate
12
Zinc Oxide
9
cobalt carbonate
5
Inlay Glaze:
Empirical Formula inlay hiAlk_Z3P_Z3V_0:
Na2O 0.41
CaO 0.31
MgO 0.10
P2O5 0.07
TiO2 0.21
Remarks
contain substantially higher Frit 413.
glassy matrix. Generally, in this glaze family,
small increases in silica result in a greater fraction
of glassy matrix
and correspondingly fewer micro-crystals.
the greater proportion of glassy fraction over
micro-crystals that I've observed with small increments
of silica.
the first two glazes.
Custer Feldspar analysis have been reported as not entirely
reliable. Thus it is likely that the
UMF's of these glazes differ by more
than is apparent.