Dalmation Spots
This bowl is glazed with a high strontium glaze sr_Z40_PAl. It is turquoise
if applied sufficiently thickly
bowl is ~ 4 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 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 hour hold at 1650 deg F
K2O 0.11
Al2O3 0.56
SiO2 2.98
molecular percent Silica 65.6%
Added:
3% copper oxide
as on the inside of this bowl. The dark,
nearly black markings, are a second phase, a frequent feature seen in
high
strontium glazes. I fancifully refer to these as Dalmation spots.
Image of the glaze sr_Z40_PAl
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 sr_Z40_PAl :
Na2O 0.23
CaO 0.27
MgO 0.01
SrO 0.38