Slate Velvet Underglaze is a dark, bluish-gray at cone 05 that darkens to a deep, slatey shade when fired to cone 5 and transforms into a melancholic blue-green at cone 10. A clear glaze accentuates the color of the underglaze significantly at any temperature.
Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination.