Molybdenum Crystalline Glazes

   Little is written about molybdenum as a glaze material. Our limited research has turned up a bit of information. It was discovered in the latter part of the 18th century by a Swedish scientist, Carl Wilhelm Scheele. We are unsure who brought the technical use of molybdenum in glazes to the U.S. from Europe. We do start seeing its use during the Arts and Crafts pottery period made during the turn of the twentieth century. The potters of whom we are aware who experimented with molybdenum crystalline glazes are Adelaide Robineau, Charles Fergus Binns, Frederick H. Rhead, Otto and Gertrude Natzler, and Herbert Sanders.
   An excerpt by Phyllis Ihrman, from Peggy Weiss’ book about Adelaide Alsop Robineau gives a good description, “The molybdenum crystal is very elusive, less predictable, and more difficult to achieve than most other types of crystal. It differs from the zinc silicate and titanium crystal in that it is usually quite small and shaped like a rectangle, star, or diamond. In multitude they are double refracting, separating light into different colored rays. They seem to float on the surface of the glaze and display all the iridescent colors of the rainbow as light plays over them. The matrix is usually very lustrous and opaque. Often the crystals are very subtle only being seen when the pot is tipped to catch the light.”(1)

(1) Weiss, Peg, Adelaide Alsop Robineau Glory in Porcelain, Syracuse University Press, New York, 1981, page 150.

Close-up photograph of the surface of one of our glazed art pieces (unmagnified). The crystals vary in size from pin point to 1.5 inches across.