Notes
Old number: 183
Related Information
Each Mason stain has its own personality for coloring the body
These Mason stains make the porcelain more refractory, but some more so (e.g. 6385, 6226). Some do not develop the intended color (e.g. 6006 pink, it is a glaze stain only). Some need a higher concentration (e.g. 6121, 6385). Some need a lower concentration (e.g. 6134). Some do not impart a homogeneous color (e.g. 6385). The data sheets from the stain manufacturer normally make it clear which of their stains are suitable in bodies. But it is up to you to test concentrations needed to get the desired color and what adjustments to the porcelain are needed to compensate its degree of vitrification in response to the effects of the stain.
Mason stains in the G2926B base glaze at cone 6
This glaze, G2926B, is our main glossy base recipe. Stains are a much better choice for coloring it than raw metal oxides. Other than the great colors they produce here, there are a number of things worth noticing. Stains are potent colorants, the percentages needed are normally much less than metal oxides. Staining a transparent glaze produces a transparent color, it is more intense where the glaze layer is thicker, this is often desirable in highlighting contours and designs. If you add an opacifier, like Zircopax, the color will be less intense, producing a pastel shade the more you add. The chrome-tin maroon 6006 does not develop well in this base (alternatives are G2916F or G1214M). The 6020 manganese alumina pink is also not developing here (it is a body stain). Caution is required with inclusion stains (like #6021), the micro-bubbling here is not likely because it is overfired (it is rated to cone 8), adding 1-2% Zircopax normally fixes this issue.
A glaze incompatible with chrome-tin stains (but great with inclusion stains)
Left: A cone 6 matte glaze (G2934 with no colorant). Middle: 5% Mason 6006 chrome-tin red stain added. Right: 5% Mason 6021 encapsulated red stain added. Why is there absolutely no color in the center glaze? This host recipe does not have the needed chemistry to develop the #6006 chrome-tin color (Mason specifies 10% minimum CaO, this almost has enough at 9.8%, but it also has 5% MgO and that is killing the color). Yet this same glaze produces a good red with #6021 encapsulated stain at only 5% (using 20% or more encapsulated stain is not unusual - so achieving this color with only 5% is amazing).
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.
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