surface crystals
Here is a gloss glaze with has mini surface crystals, sufficiently large to be
visible without magnification. These crystals are visible as discrete
disks
Closeups of the crystals are shown and, for context, a picture of the pot.
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 20 minute hold
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 .27
Al2O3 .71
SiO2 3.62
molecular percent Silica 67.8%
The inside of this pot is a glossy, crazed, copper green with a scattering of
mini-crystal clusters. The outside of this bowl has regions
As is seen in the above close up images, these crystals are translucent at
their edges.
What are those crystals?
only if the glaze is applied thickly. Applied thicker still, these
crystals merge to form what initially would appear as a micro-crystalline
matte surface.
Close up Images of the Crystals
Image of the piece
bowl with glaze copperYellow_Z26_1MSi
bowl is ~4 in diameter
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 copperYellow_Z26_1 + 1% copper carbonate:
Na2O .27
CaO .25
MgO .12
ZnO .09
Remarks
of tan matte
which, as seen in the closeup images, are merged clusters of the same
mini-crystals that are seen on the inside of the bowl.
The individual
crystal clusters are ~ 1/8th of an inch in diameter; sufficiently large as to
be visible without magnification.