This is G2934Ymatte glaze base with opacifiers added. It has been applied to a dark-burning body to demonstrate the comparative degrees of opacity. The stain is Mason 6700 white. While it does not opacify nearly as well as tin or zircon, it does produce a smoother surface.
Opacifier Glaze opacity refers to the degree to which it is opaque. There is more than meets to eye to the subject of opacity control.
Ceramic Stain Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.