Tin oxide is a powerful opacifier, but the 5% in the glaze on the left is clearly not enough. 10% more zircon had to be added to produce the one on the right.
Glaze opacity refers to the degree to which it is opaque. There is more than meets to eye to the subject of opacity control.
Majolica is white opaque glazed red earthenware clay having colored overglaze decoration. But if you know more about what it is technically you will have more control of your product.
The term Terra Cotta can refer to a process or a kind of clay. Terra cotta clays are high in iron and available almost everywhere. While they vitrify at low temperatures, they are typically fired much lower than that and covered with colorful glazes.
Sign up at the home page.