Cone 6: Sandstone is a matte, off-white glaze that contains a variety of brown crystals that melt during the firing. Thicker application and heavy crystal concentration will produce more glossy blue/purple variation.
Cone 10: Color darkens. Glossy blue/purples become more prominent.
*The first image is cone 6 and the second image is cone 10.
Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination.