A finely ground, naturally occurring Calcium Carbonate, 98% pure. Balance of components, silica or magnesium. As used in better grade glazing compounds or for cleanup after glazing. Stained Glass Whiting Powder is a versatile and essential supply for glass art and mosaic projects. This 1.5 lbs bag of powder is perfect for creating a white base for your stained glass designs. Whether you are a beginner or a seasoned artist, this product will help you achieve beautiful and professional results in your craft endeavors. So, add this essential supply to your collection and unleash your creativity in the world of glass and mosaics.