Earthenware glaze test in the form of an egg, white glazed, test piece egg soil finds ceramic earthenware glaze tin glaze, hand turned glazed baked Earthenware glaze test in the form of an egg. White glazed discolored by staying in the soil. On the underside four points of prunes Glaze tests are usually convex and round from above. Not only the color of the glaze was tested, but also the degree of liquefaction and adhesion of the enamel archeology Rotterdam Heliport terrain indigenous pottery test pottery mixing craft Soil discovery: Heliport site Rotterdam June 1978.