Iron colors in High Alumina Glazes

firing to cone 10 in oxidation

slow downfire at 50 deg F an hour in the interval 1850 deg F to 1700 deg F

slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F

One hour hold at 1650 deg F

Continuing exploration of low iron high alumina glazes -

The second glaze has higher alumina and higher Li2O with less iron that the first glaze, the reference glaze.

The shift in color seen in the second glaze is likely the result of increased Li2O, and decreased Fe2O3.

The stain in the masked design in the second glaze is Custer Feldspar + Rutile.

These are high alkaline glazes, with total CaO plus MgO ~.06 the residual impurities in the feldspars and clays.