The clay is Plainsman H431. Fired at cone 10R. Tony learned how to make these bowls from John Porter in the early 1970s. They were glazed on the inside with the rough, bare clay surface on the outside. Decoration was done by a wax resist technique. The glaze is a silky dolomite matte with rutile and a little cobalt added for the powder blue color.
Tony Hansen is the author of Digitalfire Insight, Digitalfire Reference Library and Insight-Live.com, he is a long-time potter, ceramic lab-technician and body and glaze developer.