By Goho, Alexandra
Science News , Vol. 167, No. 11
While sifting through 15th- and-16th century documents at the state archives in Venice, Louisa Matthew came across an ancient inventory from a Venetian seller of artist's pigments. The dusty sheet of paper, dated 1534, was buried in a volume of inventories of deceased persons' estates.
As Matthew, an art historian at Union College in Schenectady, N.Y., scanned the more-than-l00 items on the list, she realized that it was exactly what she had dreamed of finding. "I remember thinking, 'Did someone plant this here?'" she says. 'And why hadn't anyone noticed this before?" This inventory of artists' materials could hold the answer to a question that had long vexed conservation scientists: How did Venetian Renaissance painters create the strong, clear, and bright colors that make objects and figures in their paintings appear to glow?
The diversity of items on the list amazed Matthew. It included not only painters' pigments such as azurite, vermilion, and orpiment, but also raw materials used in a variety of crafts. "So, it wasn't just the painters who were buying from the color seller," she says. Glassmakers and dye-makers were also frequenting the shop. If the color shop was a nexus for all these different craftspersons, she reasoned, "maybe they were sharing ideas"--and materials too.
That last speculation spurred Matthew's colleague Barbara Berrie, a conservation scientist at the National Gallery of Art in Washington, D.C., to reexamine the Venetian paintings that she had been studying for the past few years. Previous analyses of microscopic paint samples taken from a handful of works had revealed many aspects of the artists' techniques, such as their process of layering colors, but art historians had found few recipes detailing how Venetian artists made their colors. "The materials on this inventory list suggested that we needed to look more widely," says Berrie.
Sure enough, when she re-analyzed her paint samples, she found a variety of types of glass particles mixed with the paint.
"It's a very exciting finding," says Jennifer Mass, who heads the conservation-science lab at Winterthur Museum in Delaware, adding that the optical properties of glass might explain the clarity and translucency of Venetian paints, which capture and reflect light in distinctive ways.
These findings and reports by several other conservation scientists imply that Italian Renaissance artists weren't merely painters. They were also experimental chemists who mixed and matched unconventional ingredients. Says Berrie, "They used new materials to create an art for their time."
SILICA GALLERY The presence of glass in Venetian paintings makes sense historically. "During the Renaissance, Venice was the glassmaking capital of the world," says Mass. By the late 15th century, the glassmaking industry was burgeoning, and with it came the creation of high-quality colorless glass, called cristallo, that was prized throughout Europe for its transparency and clarity.
Venetian glassmakers also made a wide variety of brilliantly colored glass objects.
Since Venice was a major port, it received textiles, dyes, ceramics, gems, and other goods from all over the East. These imports inspired the local craftspeople. For instance, to satisfy the Venetians' growing taste for ancient and expensive artifacts, glassmakers figured out how to make fake precious and semiprecious stones out of colored glass. "It was a time of tremendous innovation," says Matthew.
In an age of new ideas, it's no coincidence that Venetian painters exploited novel materials to expand their art. Before Berrie's discovery of glass particles in paintings at the National Gallery, she had some evidence suggesting that Venetian painters experimented with other unconventional materials.
The artist Lorenzo Lotto kept a painting notebook in which he listed materials that he bought. Among them were mercury and sal ammoniac (ammonium chloride), the latter being a white or colorless crystalline salt found in volcanic regions. …