Glaze Reactions in an altered firing
The matrix glaze and inlay glaze shown here were seen previously
here:
This is an exploration of a firing which has a slow up-fire in addition to
having the usual holds
An iron matrix glaze, with silvery micro-crystalline inclusions, has a glossy
blue-green inlay. The
The matrix (i.e., background) glaze and inlay glaze overlap minimally before
firing. The width of the
The background glaze is oribe-satIron; the inlay design is glazed with
oribe-woof-PAlkAl-PSiMg
The design is created by adhering a mask and then applying the main
glaze. After drying,
The close-up images were heavily edited to enhance detail and colors are
brighter as a result.
150 deg F an hour to 250 deg F
300 deg F an hour to 2050 deg F
120 deg F an hour to 2250 deg F then a 1 hr hold at 2250 deg F
90 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 2 hr hold at 1850 deg F
300 deg F an hour to 1750 deg F then a 1 hr hold at 1750 deg F
300 deg F an hour to 1700 deg F then a 3 hr hold at 1700 deg F
25 deg F an hour to 1650 deg F then a 1 hr hold at 1650 deg F
K2O 0.15
Al2O3 0.52
SiO2 3.39
molecular percent Silica 65.57%
Added:
5.0% cobalt carbonate
K2O 0.17
Al2O3 0.35
SiO2 3.3
molecular percent Silica 70.68%
Added:
5.0% Copper Oxide
This firing features a 'rounded at the top' firing profile; with a hold
of an hour 60 degreesF
The results in this firing are distinct; the sharp pointed edges indicate
crystal growth,
The inlay was three quarters of an inch in width that, together with a liberal
inlay glaze application,
on the way down. In order for crystals to grow in
a glaze, the oxides which will grow the crystals must
first dissolve into
the glaze matrix. Here, by contrast with the prior results, by giving the
glaze
additional time to melt on the way up, crystals are seen to have
grown both in the inlay itself, and
in the interaction zone of the inlay
and background glaze.
resulting design has fragments of glassy blue
edged in contrasting dendritic crystals. In addition,
acyclic snowflake-like
crystals are seen in the inlay glaze.
original inlay varied from an eighth of an inch to
three quarters of an inch, is considerably thicker than my
usual inlay.
the mask is removed and the open area filled in with a
second glaze, using a bulb syringe
with a needle applicator.
The colors of the full image of the bowl are as they
appear in bright light.
Close up Images of the interaction region
Image of the piece
bowl with glaze oribe-satIron and inlay glaze oribe-woof-PAlkAl-PSiMg
bowl is ~6 inches in diameter
oxidation firing to almost cone 11 in an electric kiln
Firing profiles
Up Fire profile hot cone 10
Down Fire Profile hot cone 10
Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.
glaze composition
Empirical Formula oribe-satIron :
Na2O 0.28
CaO 0.39
MgO 0.18
Fe2O3 0.21
P2O5 0.05
Inlay Glazes:
Empirical Formula oribe-woof-PAlkAl-PSiMg:
Na2O 0.05
CaO 0.49
MgO 0.29
P2O5 0.01
Remarks
below top temperautre, and a slow climb from there to
the top temperature.
as do the large 'snowflake-like' features seen in the
inlay.
caused substantial flows of the inlay through the
background glaze. The shape of this inlay differs
from that seen in the
previous note and accounts for some of the differences in the appearance of
the
inlay and interaction region. That said, The large flat snowflake-like
crystals seen in the inlay are new to
this firing.