The Color that Changed the Course of Art

Still Life, 17th century, Paul Liegeois.
"True blue, royal blue, ultramarine: During the Renaissance, these were all names for the most prized of all pigments, lazurite, derived from the semiprecious mineral lapis lazuli. Mined and processed since the sixth century almost exclusively in Afghanistan, and imported to European markets through Venice, it was worth more than five times its weight in gold. It was used sparingly, often reserved for the richest patrons by the most prosperous artists. Look at this sumptuous still life, for example, painted in mid-17th-century Paris by Paul Liegeois, featuring his signature royal blue drapery. He achieved the effect with thin glazes of ultramarine oil paint applied over a layer that was highlighted with white lead. When light penetrates the thin blue glaze, the white reflects it back, intensifying a deep blue hue. ..."
the iris

The Seine at Charenton, 1874, Jean-Baptiste Armand Guillaumin.