V328 Iceberg BlueProduct Description V 328 Iceberg Blue Velvet Underglaze is a light blue color that is powder blue at cone 05, slightly darker at cone 5, and maintains its light blue shade up to cone 10. A clear glaze over Iceberg Blue tends to lift the color out slightly, lightening it. Safety Warning Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination.