Smalt Deep Coarse Pigment

Description

Smalt Deep Coarse (PB32) is a handmade single-pigment smalt composed of potassium cobalt silicate glass ground to a coarse particle size. It produces a deep, historic blue with a cool, rich undertone and a strongly textured, granulating masstone. Compared to modern cobalt or phthalo blues, this pigment is lower in chroma and far more transparent, offering a softly weathered, Old Master blue rather than a high-intensity modern color.

In use, Smalt Deep Coarse gives a subtle, atmospheric blue ideal for historical palettes, skies, distant architecture, drapery, and veiled glazes in landscape and figurative work. It has low tinting strength and a transparent to semi-opaque character, making it easily overpowered in mixtures but exceptional when used generously in washes or layered over more opaque undercolors. The Deep Coarse grind produces darker, more dramatic texture than fine smalt, with pronounced granulation and a distinctive mineral scatter in wet-in-wet passages and on rough papers.

This cobalt glass pigment is chemically stable as a glass but historically known to be more reliable in fresco and water-based media than in oil, where very long-term discoloration can occur. In artist's colors it offers a uniquely historical, mineral blue that serves as a subtle mixer and a characteristic statement color for work inspired by Renaissance and Baroque techniques, or for painters who prize strong granulation and visible pigment texture.

History

Smalt is one of the earliest cobalt-derived blues and was widely used in European painting from the 15th to the 18th centuries as an affordable substitute for natural ultramarine. It is made by melting silica (quartz), potash, and cobalt-bearing ores into a deep blue glass, then quenching and grinding the frit into pigment. Historically, different grades were classified by particle size: coarse smalt was favored for the deepest, most intense blues and the strongest textural effects, while finer grades yielded paler, smoother color.

Painters of the Northern and Italian Renaissance, as well as Dutch and Flemish masters, frequently used smalt in skies, draperies, and glazes, often in combination with ultramarine. Over time, however, some smalt-containing oil paintings were observed to fade or gray due to interactions between the potassium-rich glass and the oil binder. With the 19th-century introduction of synthetic ultramarine and cobalt aluminate blues, smalt largely fell out of regular use and survived mainly in glassmaking, ceramics, and conservation work. Modern artist-grade smalt, particularly in coarse, deeply granulating grades like Smalt Deep Coarse, revives this historic pigment for those seeking its unmistakable mineral texture and softly aged blue character.

Pigment Information

Pigment Type: Synthetic (Inorganic) sodium cobalt silicate glass (smalt)

Suitable Mediums: Watercolor, Oil, Tempera, Acrylic, Encaustic, Cold Wax, Casein, Milk, Swedish Flour, Lime / Fresco

Lightfastness: Good

Opacity: Transparent to semi-opaque

Other Names: Smalt Deep Fine, Smalt, Potassium Cobalt Silicate Blue

Color Index Code: PB32