These are Mason stains added to the cone 6 G2934 silky MgO matte liner base glaze (with tin, zircopax and various stains added). The brightest colors (6600, 6350, 6300, 6021, 6404) were tested overnight in lemon juice without visible changes. It is known that MgO mattes are less prone to acid attack that CaO mattes. Caution is required with inclusion stains (like #6021), if they are rated to cone 8 they may already begin bubbling at cone 6 is some host glazes.
G2934 - Matte Glaze Base for Cone 6
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte.
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.
In traditional ceramics and pottery dipping glazes can be of two main types: For single layer and for application of other layers overtop. Understanding the difference is important.