Why is zen porcelain "premium"? The world's finest refined and natural minerals: Clay and bone ash. Zen premium porcelain dishes are made at high temperatures with a mixture of pure and high-quality ingredients. The strength and integrity of our porcelain are due to our effort to use only first-class raw materials and to thoroughly heat these raw materials in a 2-stage firing process. This ensures maximum strength, durability, and lightness. In addition, our products remain thin and have long-lasting colors.