bubble artifacts in glaze
The strange marking found in the surface of this glaze are the residual artifacts
of bubbles forming in the glaze
The network of rings seen on both the inside and outside of this bowl, mark
the location of the now healed bubbles
To me, this pattern looks like the underside of a bubble froth on a transparent
surface.
To enhance the circular features I see in the surface, I've played about with
photoshop, the results are
This glaze was derived from the second glaze shown here:
iron_satIron_Z2T_0MAlk has less alkali metals, less silica, and more alumina,
so is expectedly
This glaze looks nothing like these pictures! These images emphasize
the collapsed bubbles,
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 0.25
Al2O3 0.71
SiO2 3.88
molecular percent Silica 66%
K2O 0.23
Al2O3 0.66
SiO2 4.19
molecular percent Silica 68%
Bubbles form in a glaze as it matures. As noted above, this glaze,
iron_satIron_Z2T_0_MAlk,
I see a pattern that resembles the edges of bubbles and, as noted above, the
existence of healed bubbles
The striking difference in color between the inside and outside of the bowl is
real, The glaze application
during maturation. These bubbles healed
and were reabsorbed by the glaze at a temperature close to the
maximum
temperature reached before cooling. A smooth surface remains, though with
inhomogeneities in the
surface composition.
in the surface.
the images of the surface features shown. I
also show images of the pot.
more refractory.
Image of the glaze iron_satIron_Z2T_0_MAlk
inside
outside
bowl is is 3 inches in diameter
Images of the surface modified to make bubble artifacts more
visible
while severely distorting the glaze.
the entire inside of bowl
an enlarged fraction of the modified image of the inside of bowl
an enlarged fraction of the modified image of the outside of bowl
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_satIron_Z2T_0_MAlk :
Na2O 0.38
CaO 0.26
MgO 0.11
Fe2O3 0.21
P2O5 0.06
Empirical Formula iron_satIron_Z2T_0 :
Na2O 0.44
CaO 0.22
MgO 0.11
Fe2O3 0.22
P2O5 0.05
Remarks
expectedly has a higher maturing temperature. A
glaze with unhealed bubbles is underfired.
Bubble artifacts could be
expected in an almost underfired glaze.
is a plausible assumption. So, I rolled it
all together and decided I was seeing bubble residue in a marginally
mature
glaze.
on the inside of the bowl is thicker. This is
that rare situation where a thin glaze application of a saturated
iron glaze
is more attractive.