This color contains the following pigments:
complex silicate of sodium and aluminum with sulfur
Na8-10Al6Si6O24S2-4 or Na6-8Al6Si6O24S2-4
Ultramarine is the standard warm blue, a brilliant blue pigment that has the most purple and least green in its undertone. It has a moderate to high tinting strength and a beautiful transparency. Synthetic Ultramarine is not as vivid a blue as natural Ultramarine. Ultramarine dries slowly in oil and tends to produce clean, though granular, washes in watercolor. French Ultramarine mixes well with Alizarin colors in oil and watercolor form to create a range of purples and violets. It can dull when mixed with white in acrylic form, but mixes well with other colors. The shade varies based on manufacturer. Considered a great color for glazes, it is not suitable for frescoing.
Ultramarine has excellent permanence, although synthetic Ultramarine is not as permanent as natural Ultramarine. It may discolor if exposed to acid because of its sulfuric content.
Ultramarine has no significant hazards.
The name for this pigment comes from the Middle Latin ultra, meaning beyond, and mare, meaning sea, because it was imported from Asia to Europe by sea. It is a prominent component of lapis lazuli and was used on Asian temples starting in the 6th century. It was one of the most expensive pigments in 16th century Europe, worth twice its weight in gold, and so was used sparingly and when commissions were larger. Ultramarine is currently imitated by a process invented in France in 1826 by Jean Baptiste Guimet, making blue affordable to artists and extending the range of colors on their palettes.
organic, vat dyes
complex, insoluble anthraquinone
Indanthrene Blue is a clear, clean, deep blue organic pigment. It has moderate to high tinting strength and is not as overpowering as Phthalo Blue. Hansa Yellow Deep, Benzimidazolone Orange, and Raw Umber are its best mixing complements.
Indanthrene Blue is permanent with excellent lightfastness in both masstone and tints.
Indanthrene Blue varies in its acute toxicity, though toxicity is generally slight.
Indanthrene Blue is the oldest vat dye, discovered and patented in 1901 by Rene Bohn. It is considered the first anthraquinone vat dye, a group of dyes characterized by excellent lightfastness. The pigment originates from this dye.