Calico again
Here again, after a long hiatus, is the calico effect, Strongly colored
markings with sharply defined margins.
Here is an example of the
calico glazes I worked on in 2016.
As previously, the starting point is a modification of the glaze 404 from
Emmanuel Coopers book
I am starting over, with lower silica:alumina ratio than in prior work.
Inside of bowl:
Outside of bowl:
Inside of bowl:
Outside of bowl:
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 0.20
Al2O3 0.33
SiO2 2.12
molecular percent Silica 61.5%
K2O 0.14
Al2O3 0.33
SiO2 2.4
molecular percent Silica 64.5%
The glaze cooper_404_1_MSi shows pitting in the center of the bowl as a result
of an unduly heavy glaze application.
The glaze on the outside of each bowl is half the thickness of that on the
inside, yet in both cases the calico markings
"The Potters Book of Glaze Recipes".
The glazes
cooper_404_1_MSi
bowl is ~3 inches in diameter
glaze cooper_404_1_EU
bowl ~3 inches 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 cooper_404_1_MSi :
Na2O 0.08
Li2O 0.07
BaO 0.25
CaO 0.02
MgO 0.01
ZnO 0.37
Empirical Formula cooper_404_1_EU :
Na2O 0.22
BaO 0.22
CaO 0.03
MgO 0.01
ZnO 0.38
Remarks
It is a dry stony glaze, slightly
underfired. This glaze will require much additional work to be usable on
utilitarian ware.
are visible on the
outside. In prior work, the markings were visible only with a thick
application of glaze.
As these are all immensely viscous glazes, the
result was a high risk of dunting.