The slips and glazes shown on this website have been tested on Coleman Porcelain. This gives us a "base" color pallet for the true color of the finished slips and glaze combinations. Just like painting a wall- the color of the clay body underneath will influence the finished color of your glaze. The only real (clean) porcelain is made with Kaolin (not ball clay). And, it has a high percentage of silica (glass). This gives you a good "melt" with your glaze and gives the surface more depth. This quality is why we love to work with porcelain in cone 10 reduction.