Pulling purple from the ocean floor

The key ingredient to another expensive pigment lurked in ocean waters. A secretion from the predatory sea snail Bolinus brandaris (originally known as Murex brandaris) provided the base for the deep, blue-red hue known as Tyrian purple, explained Khandekar. Its high cost rendered it a status symbol, and Byzantine emperors forbade anyone outside the imperial court from using the violet dye, lending it the distinction “royal purple.”

Shiny, precious metal

There are small jars of shimmering metal pigments, often found in automotive finishes, that gradually made their way into 20th-century pop art. English painter and collage artist Richard Hamilton was fond of spraying the metal flakes, suspended in a binding medium, on his works to give his art a shining glow, said Khandekar. “They are kind of extraordinary, these tiny bits of metal that you find on various works.”

Of crimson origin

There are samples of kermes, an Old World pigment created by grinding tiny blisters produced by the insects Coccus ilicis, which lived on the kermes oak tree. Harvard’s sports teams, students, and alumni everywhere owe a debt of gratitude to the little bugs: Kermes is also the source of the word “crimson.”

Deadly beauty

Some pigments must be handled with care, including the yellow-hued orpiment and the red-orange realgar, which are derived from arsenic sulfide minerals.

Similarly, the crystalline powder copper acetoarsenite, a brilliant shade of emerald green, could be hazardous to an artist’s health. The pigment produced the vibrant background found in the Fogg Museum’s “Self-Portrait Dedicated to Paul Gauguin” by Vincent van Gogh. But it was also highly toxic. Inexpensive to make, the color became a popular shade for household paint near the end of the 1800s and into the early 1900s, but its fumes could prove deadly. Later, the inorganic compound was used in insect repellant. “The ultimate intent is to get the right color,” said Khandekar, “but often artists will take great risks in doing so.”

Red is for Rothko

In recent years, working with the collection helped experts to develop an innovative “virtual” restoration. After analyzing Lithol red, the pigment favored by abstract artist Mark Rothko, Khandekar and a team of scholars developed a technique that used light from a projector to augment the faded colors on a series of Rothko murals that the artist painted for Harvard.

“We found that when you tried to fade Lithol red as a powder, it was incredibly stable, but when you mixed it with ultramarine blue and a binding medium it became incredibly light-sensitive. Our analysis helped us understand what was going on with the paint,” said Khandekar. “To be able to treat and best look after works of art, you need to know all the things that are going on with them, and the Forbes Pigment Collection helps us do that.”