John McCain on sat 12 apr 97
Kevin O'Hara asked about a reliable base formula for an ash glaze. We
have been using the glaze base provided by Harold McWhinnie in his
November 1986 'Ceramics Monthly' article (A Multipurpose Glaze, p. 75).
We repeat it below.
If you have any questions about this glaze, we believe that Harold is
now monitoring the Clayart list regularly.
BASE GLAZE (Cone 8-10)
Gerstley Borate - 8.45
Magnesium Carbonate - 1.86
Whiting - 15.30
Wood Ash - 14.54
Custer Feldspar - 15.55
Georgia Kaolin - 10.91
Flint - 33.39
For a Cone 6 glaze, Nepheline Syenite can be substituted for the Custer
We have experimented with various types of wood ash. We now use pecan
hull ash. Fortunately, we have many pecan trees in the area along with
cracking plants that kindly supply us with the hulls. There is a lot of
oil in pecan hulls (including many nuts) so they burn hot with very
little but fine ash. We do not wash this ash; however, we have found
that we must wash other wood ash. We experimented with Victoria's
Secret ash (burned their ceasely catalogs) but found it full of trash
and required cleaning.
John and Judy McCain
Palo Pinto Pottery