The hues in the Forbes Collection include the esoteric, the expensive, and the toxic.Photograph by Jason Fulford for The New Yorker

How blue can it get? How deep can it be? Some years ago, at the Guggenheim Bilbao, I thought I’d hit on the ultimate blue, displayed on the gallery floor. Yves Klein, who died at thirty-four, was obsessed with purging color of any external associations. Gestural abstraction, he felt, was clotted with sentimental extraneousness. But, in search of chromatic purity, Klein realized that even the purest pigments’ intensity dulled when combined with a binder such as oil, egg, or acrylic. In 1960, he commissioned a synthetic binder that would resist the absorption of light waves, delivering maximum reflectiveness. Until that day in Bilbao, I’d thought Klein a bit of a monomaniacal bore, but Klein International Blue, as he named the pigment—rolled out flat or pimpled, with saturated sponges embedded in the paint surface—turned my eyeballs inside out, rods and cones jiving with joy. This is it, I thought. It can’t get any bluer.

Until YInMn came along: the fortuitous product of an experiment in the materials chemistry lab at Oregon State University in 2009. Intending to discover something useful for the electronics industry, Mas Subramanian and his team heated together oxides of manganese, yttrium, and indium at two thousand degrees Fahrenheit. What emerged was a new inorganic pigment, one that absorbed red and green light waves, leaving as reflected light the bluest blue to date. Subramanian sent a sample to the Forbes Collection in the Straus Center for Conservation and Technical Studies, at Harvard University, where it sits with twenty-five hundred other specimens that document the history of our craving for color.

Among the other blues on the Forbes’s shelves is Egyptian Blue, a modern approximation of the first synthetic pigment, engineered five millennia ago, probably from the rare mineral cuprorivaite, a soft mid-blue used for the decoration of royal tomb sculpture and the wall paintings of temples. Later, blues strong enough to render sea and sky were made from weathered copper-carbonate azurite—crystalline bright but sometimes darkening in an oil binder. In 1271, Marco Polo saw lapis lazuli quarried from a mountain at Badakhshan, in what is now Afghanistan. Laboriously prepared by removing impure specks of glinting iron pyrite, it became ultramarine—as expensive, ounce for ounce, as gold, and so precious that it was initially reserved for depictions of the costume of the Virgin. In addition to these, the Forbes Collection has a poor man’s blue—smalt made from crushed cobalt containing potassium glass, which weakens, eventually, to a thin greeny-brown gray.

The Forbes Collection owes its existence to a belief in the interdependence of art and science, but it is also an exhaustive archive of cultural passion. A display features Vantablack, which absorbs 99.96 per cent of light, and has to be grown on surfaces as a crop of microscopic nanorods. In 2016, the sculptor Anish Kapoor saw the pigment’s potential for collapsing light, turning any surface into what appears to be a fathomless black hole, and he acquired the exclusive rights to it. An outcry from artists, who objected to the copyright, prompted the Massachusetts manufacturer NanoLab to release Singularity Black, created as part of the company’s ongoing research with NASA, to the public, and the artist Stuart Semple to make the World’s Pinkest Pink available to any online buyer willing to declare himself “not Anish Kapoor.” But Kapoor obtained a sample of the pink pigment, and used it to coat his middle digit, which he photographed and posted online for Semple.

Narayan Khandekar, the head of the Straus Center for Conservation and Technical Studies, takes pleasure in such skirmishes, secure in the knowledge that he presides over something weightier: a priceless resource for understanding how works of art are made, and how they should be preserved.

The Department of Conservation and Technical Research was founded, in 1928, by Edward Waldo Forbes, the director of Harvard’s Fogg Museum from 1909 to 1944. Today, the Forbes’s vast library of color and its technical laboratories are housed in the museum’s steel-and-filtered-glass rebuild, designed by Renzo Piano. Rows of pigments in tubes, jars, and bowls are visible through the doors of floor-to-ceiling cabinets. Khandekar had the winning idea of displaying them as if unspooled from a color wheel: reds at one end, blues at the other. There are the products of nineteenth-century chemical innovation—viridian green, cadmium orange, and the chrome yellow with which van Gogh was infatuated but which, over time, has begun to darken his sunflowers. But at the heart of the Forbes Collection are the natural pigments that were the staples of painters’ inventories before chemically synthesized paints replaced the impossibly esoteric, the dangerously toxic, the prohibitively expensive, and the perilously fugitive.

Among those relics is Dragon’s Blood, reputed in antiquity and in the Middle Ages to have got its vividness from the wounds of dragons and elephants locked in mortal combat. The pigment actually owed its intense redness to the resin secreted from trees growing on the islands of Socotra and Sumatra, especially the rattan palm and the Dracaena draco. The Forbes’s sample is now a dusty rose—not so unlike the nineteenth-century pigment called la cuisse de nymphe emue (“the blushing thigh of an aroused nymph”)—having faded, most likely, from exposure to high light levels. Even in the early fifteenth century, the Italian painter Cennino Cennini warned in his practical manual, “Il Libro dell’Arte,” that artists beguiled by the pigment’s reputation should “leave it alone, and do not have too much respect for it; for it is not of a constitution to do you much credit.” Better to stick to madder root, red ochre, or the red-lead minium that had been in use since classical antiquity.

Other Forbes specimens have better preserved the poetic mystique of their origins. There is a murex shell from the Eastern Mediterranean, a quarter million of which were needed to make a single ounce of Tyrian Purple, the color used in the Roman Republic to edge the togas of the powerful. There is a loaf of toxic tawny-red cinnabar. (Buy it in solid cakes, Cennini advises, lest some scoundrel has adulterated the stuff with brick dust.) There is the copper-arsenite Scheele’s Green, synthesized at the beginning of the nineteenth century and more dazzling than traditional verdigris, the green-blue patina given off by corroded copper. A later variant of Scheele’s, Paris Green, equally toxic and even brighter, was so cheap to produce that it coated Victorian wallpapers, children’s toys, and—despite early evidence of its toxicity—even confectionery. Following Napoleon’s death, in 1821, some Bonapartists put it about that the British had poisoned their hero by having him sleep in a green room, the paper releasing arsenic vapors in the damp sea air.

A selection of pigments from the Forbes Collection.Photograph by Jason Fulford for The New Yorker

For Edward Waldo Forbes, pigment hunting and gathering was not just a matter of creating an archive of lost or languishing color. It was about the union of art and science. His pedigree embodied the paradox: one of his grandfathers was the railway magnate John Murray Forbes; the other, the transcendentalist philosopher-poet Ralph Waldo Emerson. With a Massachusetts schooling, culminating, inevitably, at Harvard, Forbes was a typical product of the generation who believed that Gilded Age materialism could be redeemed by the “Western civilization” that the social critic and art professor Charles Eliot Norton eulogized in the art-history lectures that Forbes attended as an undergraduate. The moral purpose of that civilization was the conversion of raw wealth into beauty and humanism. Guided by this principle, Forbes read English at Oxford for two years, and travelled through Europe, spending time in Italy. Still, he resented the condescending European assumption that the New World would never really rise above breathless cultural tourism. Serious art history was supposed to change that, and in 1900 Wellesley College became the first in America to offer a degree in the subject. But teachers at Wellesley and Harvard had to make do, for the most part, with plaster-cast reproductions and lantern slides.

In Rome, the twenty-six-year-old Forbes bought his first Italian painting: a half-ruined, flaking altarpiece attributed to Girolamo di Benvenuto di Giovanni del Guasta—the first of many acquisitions that he made with the intention of lending them to his alma mater. Aware that Yankee buyers in Europe were being treated as easy marks, Forbes saw that, if he was to avoid being swindled, he needed to educate himself in the material construction of Old Master paintings. The claims of art and science that had shaped Forbes’s education seemed to converge. To experience the power of great painting and the romance of the original art work, as Ruskin passionately argued, the viewer must be able to recover, even to imaginatively reënact, the artist’s moment of creation. For Forbes, the varnish intended to preserve works of art had trapped them beneath a yellowing skin. But what lay beneath, exactly? And how to recover a painting’s innocence without corrupting it further?

Modern archeology, with its fastidious excavations, seemed to offer a promising model. There were also Victorian manuals on the material composition of pigments—including “The Chemistry of Paints and Painting,” by Arthur Herbert Church, one of the first scientists to hold a position at the Royal Academy of Arts, in London. In 1928, as the director of the Fogg, Forbes invited a Harvard chemistry professor, Rutherford John Gettens, to create and run a lab in its new building. Gettens’s legacy is a cabinet, near the pigment collection, that contains thousands of slides, each showing how the shade of a paint might age naturally depending on its binding medium: egg yolk, egg white, the whole egg, oils.

For Forbes, the precondition for understanding an art work lay in identifying and analyzing the materials from which it was created. In addition to collecting pigments, Forbes planted madder in his garden at Gerry’s Landing, on the Charles River, and taught the lab section of his courses at home, where students could brush gesso and lime on an assigned patch of wall or, using pigments ground at M.I.T., take a stab at Boston fresco. In pursuit of the authentic, he had resins sent from Singapore and Indonesia, and Japanese woodblock colors from his brother William, the American Ambassador to Japan in the early nineteen-thirties. Forbes set aside a small collection of these pigments in a cabinet for his students to inspect.

Khandekar allows the public to examine a small vitrine of pigments, but the main collection can be glimpsed only from across an atrium courtyard. Many of the pigments inside are still used for research. In 2007, Khandekar and his colleagues analyzed the paint in three works previously thought to have been by the Abstract Expressionist Jackson Pollock, who died in 1956, revealing a yellow pigment, PY 151, that was developed in 1969, as well as a red pigment mixed in a brown paint that was not developed until 1974, and also other media and binding not available until the nineteen-sixties and seventies. Analysis of a life-size portrait of King Philip III, of Spain, from the workshop of the court painter Juan Pantoja de la Cruz, circa 1605, which was acquired by the Fogg a century ago, revealed traces of cochineal carmine and quite possibly Mummy Brown, much darkened and deteriorated—the palette thus encompassing an empire of pigments from Egypt to Oaxaca.

A chunk of the mineral malachite, used to make the pigment Malachite Green, sits beneath a portrait of Mark Rothko taken by Herbert Matter and borrowed from the New York Public Library’s picture collection. The red spectrum is a reference to Rothko’s Harvard murals, in which the Lithol Red has faded.Photograph by Jason Fulford for The New Yorker

Khandekar was also part of the team behind the famous restoration of the Rothko murals commissioned by Harvard in 1962. Installed in the Holyoke Center, a modernist tower, the paintings were subjected to an unfiltered flow of light and the kind of casual abuse inflicted by chair backs and college catering until 1979, when conservators, curators, and university administrators, recognizing the extent of the damage, took them down. The murals were next exhibited in 1988, and Harvard received a barrage of criticism for their neglect. Some conservators have blamed the paintings’ discoloration on Rothko’s use of rabbit-skin glue as a binder; others, on his choice of Lithol Red, a low-cost powder pigment. Khandekar, who oversaw the research on the Harvard murals, suspects that their extreme fading was due to Rothko’s mixing of a calcium-salt red with synthetic ultramarine to make the purplish indigo that he so loved in his saturnine years.

Physical restoration using those colors would have made matters worse, Khandekar explained, not least because the pigments would have bled directly onto the raw canvas. Therefore, he and a team of scientists and conservationists devised a new approach to conservation, involving the projection of colored light over the paintings. When illuminated, the paintings appeared in their undamaged condition. To achieve this effect, the Straus Center’s conservation scientist Jens Stenger designed a digital “color map” of both the original paintings and the damaged murals, taking into account the fact that the various parts of the murals had degraded at different rates, according to their exposure to light. Stenger’s light projections, which restored the appearance of the original colors, had to be absolutely precise, but the result, shown in 2014, was a revelation.

This is just the kind of project that gives Khandekar and his associates at the Straus Center the greatest satisfaction. Khandekar, who was born in Sydney, is a modern personification of the Forbesian mission: a hard-core scientist converted almost mystically to the imperatives of art. His first degree was in organic chemistry. But, after a visit to the National Gallery of Victoria, Khandekar told me, “I asked myself, ‘How can a scientist spend his life with art?’ ” The conservation course at the Courtauld Institute, in London, offered an answer. Khandekar went on to practice conservation at the Hamilton Kerr Institute at the Fitzwilliam Museum, in Cambridge, England, then at the Getty Conservation Institute, in Los Angeles, before, in 2001, going to the Straus Center.

Khandekar and his lab colleagues talk about pigments in a way that is at once technically sophisticated and disarmingly naïve. Like Ruskin, they live in pursuit of the innocent romance of creation—that moment when the colors were fresh, everything dried as it was meant to, and there was no thought of the hostile work of time. As Khandekar rightly observed, while many artists are reluctant to enter the interpretive fray when discussing their own art works, most are eager to discuss materials and the physical execution of their ideas.

Khandekar’s comment brought to mind the contemporary artist Michael Craig-Martin, whose drolly indirect meditations on art’s capacity to make you believe what you don’t see included “An Oak Tree” (actually a glass of water sitting on a high shelf), but who went on to develop a radical, almost violent chromophilia. At a time when conceptual art ruled, it took guts to claim that, in fact, color is concept, and perhaps the irreducible core of painting. For such theorists as Leon Battista Alberti, it was disegno (drawing), especially from classical exempla, rather than colore, that elevated art from artisanal craftsmanship to the noble visualization of humanist ideals. Such thinking persisted. Even the Cubists saw the emerging Henri Matisse, who had dissolved plane and line in a bath of flat color in such works as “The Red Studio,” as somehow disengaged from radical ideas.