The outer glaze is Ravenscrag GR6-E Raspberry, the bright maroon color is a product of the surprising interaction between the 0.5% chrome oxide and 7.5% tin oxide present. That small amount of chrome is only enough to give the raw powder a slight greenish hue, hardly different than the clear liner. While this color mechanism appears to be effective, it is delicate. A maroon stain is actually a better choice. It would fire more consistent would be less hazardous to use. And the raw glaze will be the same color as the fired one!
GR6-E - Ravenscrag Cone 6 Raspberry Glossy
A chrome-tin burgundy glaze using the Ravenscrag cone 6 base recipe.
In ceramics and pottery, colorants are added to glazes as metal oxides, metal-oxide-containing raw materials or as manufactured stains.
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.