This is a high-melting refractory stain.
It does not fuse well in glazes, and requires a lot of flux.
It works very well in porcelain bodies.
Mason stains in the G2934 matte base glaze at cone 6
Stains can work surprisingly well in matte base glazes like G2934. But they perform differently in a matte host glaze. The glass is less transparent and so varying thicknesses do not produce as much variation in tint. Notice how low many of the stain percentages are here, yet most of the colors are still bright. A good reason to minimize stain concentration is to avoid leaching. We tested 6600, 6350, 6300, 6021 and 6404 overnight in lemon juice, they passed without any visible changes. It is known that MgO mattes, like this one, are less prone to acid attack that CaO mattes. A down-side to the MgO-matte-mechanism is that chrome-tin stains do not work (e.g. 6006), high CaO content is needed in the host glaze to develop the color. The inclusion stains 6021 and 6027 work very well in this base. As do the 6450 yellow and 6364 blue. And the 6600 produces an incredible gunmetal black. The 6385 is an error, it should be purple (that being said, do not use it, it is ugly in this base). The degree-of-matteness can be tuned by blending in some G2926B glossy base.
Cone 6 Grolleg porcelain with 10% manganese alumina pink stain
The stain is Mason 6020. The porcelain body, L3778D1. Manganese alumina stains are highly refractory, so much so that they severely affect degree-of-melting when added to glazes. They simply do not work in glazes. But in vitreous bodies, like this one, the stain has no effect on the degree of vitrification! And produces a color that is difficult to achieve in glazes.