Phosphorus in Iron Glaze
Glazes are fired at cone 6 in an electric kiln
Firing profile
A half hour hold at 1850 deg F
downfire at 50 deg F an hour in the interval 1850 deg F to 1700 deg F
downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F
A one hour hold at 1650 deg F
Clay body is a B-mix variant from Tacoma Clay Art Center.
glaze composition
satIron_4Z_5Ball
Alkali metals .2 with Li2O .19
Alkaline Earths are CaO with a trace of MgO
P2O5 .27
satIron_4Z_3
In the empirical formula:
alkali metals .7 with Li2O .26
alkali earths almost entirely CaO
alumina .42
Silica 3.2
P2O5 .09
the first pot is a cylindrical bowl ~5 inches in diameter. The second pot is a cylinder ~3.5 inches in diameter,
glaze satIron_4Z_5Ball
This glaze has molecular equivalents P2O5 .27
This glaze was inspired by Hank Murrow's observation that P2O5 is a network
former, i.e. that phosphorus is part of the chain of silica atoms that forms
the glassy structure of a glaze.
This remark together with a picture of a
students's glaze, Cory's wild was the motivation for this glaze.
Cory's wild likely was fired at cone 10, this glaze is underfired at cone 6.
There is a decorative wash over a leaf print in the leather hard glaze,
it
is seen peeking though
in the picture.
glaze satIron_4Z_3
This glaze was derived from a high alkali saturated iron glaze by replacing almost all of the magnesia with the calcia required by bone ash.
Note the striking ringed spots and the garish almost luster look to parts of the glaze.