Oil Spot
The spots in an oil spot glaze are created by the bursting of bubbles at the
surface of the glaze. Micro-crystals
The size of the oil spots is determined by the size to which the bubble can
have grown as it ascends to the surface
This glaze is quite viscous partially as the result of high alumina and low
silica:alumina ratio. The inside
The oil spots on the outside of the bowl are small and blend into the matrix.
This glaze has a surface
The design is created by adhering a mask and then applying the main
glaze. After drying, the mask is removed
bowl is ~ 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 1900 deg F then a 2 hr hold at 1800 deg F
300 deg F an hour to 1750 deg F then a 1 hr 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 0.14
Al2O3 0.89
SiO2 3.79
molecular percent Silica 63.9%
K2O 0.14
Al2O3 0.58
SiO2 2.31
molecular percent Silica 56.5%
which have grown on the inner surface of
the bubbles are then exposed, creating the contrast seen.
of the glaze. The bubbles grow
larger by coalescing of smaller bubbles, the more time available, the larger
they grow. Either thicker glaze, or more viscous glaze, slows the velocity at
which the bubbles rise,
and thus increases their size.
of this bowl was glazed nearly twice as
thickly as the outside, resulting in oil spots that are nearly a quarter inch
in diameter, and cover over half the surface area.
luster which perhaps is related to the liquid liquid
phase separation which is common in oil spot glazes.
and the open area filled in with a
second glaze, using a bulb syringe with a needle applicator.
Image of the glaze longquan-iron-shino-MLi-P-Z3K
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 longquan-iron-shino-MLi-P-Z3K :
Na2O 0.54
CaO 0.30
MgO 0.02
Fe2O3 0.17
P2O5 0.08
Empirical Formula inlay glaze inlay_Z3K_0 :
Na2O 0.82
CaO 0.02
MgO 0.02
Fe2O3 0.02
P2O5 0.18