Fine: Finer than 63 μ
Clear glass powder made from leaded crystal glass and ground into fine powder can be used in all media to give colors added luminosity or to create textural effects on the surface of paintings.
Colored and clear glass powder can be used in all media, such as oil, acrylic dispersions, lime and all kinds of glues. In certain mortars and cements, the colored glass may cause blooming. For application in exterior environments, it is advisable to do trials first. Origin and History
National Gallery of Art conservation scientist Barbara Berrie and art historian Louisa C. Matthew of Union College found that glass powder was used in the "Venetian palette" to give it extraordinary luminosity. The Venetian glass industry, centered on the island Murano in the Venetian lagoon, flourished in the late 15th century. According to Matthew and Berrie, painters obtained pigments of superior quality from "color sellers," and added pulverized glass to lend added brilliance to the hues in their pictures. Source
Colored glass is produced by melting leaded crystal glass with heavy metal oxides to achieve a wide variety of colors. The colored glass is then crushed and ground to a gritty powder less than 0.25 mm particle size. The powder is then sieved into three different grades:
Fine: Finer than 63 μ. The finest glass powder is easily worked with the brush in any media, such as watercolor, oil, acrylic dispersion, etc.
Medium: 63–106 μ. The fine powder can be used in all media; its coloring strength is better than the fine grade. The coarse powder gives brilliance and body to paint, but it may be too coarse to be applied in watercolor or glazing techniques. The glass particles are visible in thin layers.
Coarse: 106 μ and coarser. These glass particles have a sandy texture and can be strewn onto a surface; the glass particles create a glittering surface. The particles can be moved around on the surface, ideal for fresco techniques and sand-like textures. Permanence and Compatibility
The lightfastness of all colored glass powders is excellent. Colored and clear glass powder can be used in all media, such as oil, acrylic dispersions, lime and all kinds of glues. In certain mortars and cements, the colored glass may cause blooming. For application in exterior environments, it is advisable to do trials first. Oil Absorption and Grinding
Clear glass powder absorbs very little oil (18 g oil per 100 g of pigment). It has a drying effect on oil paint, because of its lead content. It is difficult to grind because of its hardness. Toxicity
Glass powders may contain lead and cadmium. Avoid dust, do not breath in dust. The dangers of lead have a cumulative effect. Utmost care should be used in handling the dry powder pigment to avoid breathing the dust. It is only moderately toxic in contact with the skin. Filler: Clear Glass Powder