Smalt "Saxon Blue"

Complex pigments are often sidelined, seen as too risky to be worth the hassle, such as pigments that tarnish, fugitive lake pigments, or dense pigments that sink and are a pain to control. However, I do sense a sort of “color resistance” among our customers; artists and craftspeople now accept the use of colors that are ephemeral, difficult to suspend, or too funny to have been used in the past as a fair price to pay to achieve new color. 

Smalt is one of those pigments. The blue cobalt glass frit was eventually adopted by the Dutch, Flemish, and Venetian Old Masters. The recipe did not originate with artists, but was adapted directly from the mining and glassmaking industries, specifically taking root in Saxony (Germany) and Murano (Venice) during the 15th and 16th centuries.

Glassmakers initially used this blue powder to tint other glass batches or sold it to ceramicists as a pottery glaze. Eventually, 16th-century colormen realized a market existed among painters and began selling the ground glass as a dry pigment for oil and fresco painting. Because the pigment was literally shattered glass, its availability depended entirely on the industrial glass supply chain.

Kurt Wehlte lists burning Smaltite (a tin-white to steel-gray metallic mineral made of cobalt, nickel, and arsenic) and Cobaltite, (a rare, metallic sulfide and arsenide mineral) to obtain Zaffer (zaffre); it is later fused with quartz and potash to form cobalt glass, which is then broken into fragments by quenching in water. Wehlte further points out these useful characteristics:

Settles out quickly
Easily wets
Poor tinting strength
Translucent
Fast drying

If manufactured for oil paints today, it presents several major challenges. First, it cannot be finely milled because it must remain coarse to retain its color, resulting in a gritty, textured paint. People want their paint to look and feel like butter. Second, it is chemically unstable in oil. Discoloration of the color happens in oil due to soap formation, where potassium leaches out, and because the refractive indices of drying oils and smalt are similar, the color results in a sad brown. Finally its high cobalt content drastically accelerates drying times, and its glass base gives it very weak tinting strength.

I find these attributes to be acceptable compromises to attain a gritty, slightly shimmering blue, which changes color with varying ambient light and angles. It often feels like I’m raking glass shards with a broom. Using a brush to paint seems enough of a restraint to satisfy my drawing hand. I don’t use this pigment in oil, but suspend it in RSG, acrylic, and watercolor binders. The video shot of my painting, before it zooms in with a microscope, is mixed with rabbit skin glue and a tiny amount of Dispersion K498 to help suspend the coarser particles.

Only available for a limited time in history, but readily available at our shop in NYC.