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Conserving Masterpieces

Today's Chemists Penetrate Mysteries of Yesterday's Art

If you could time-travel back to a Renaissance artist’s studio, imagine what you might see—a canvas just completed, still propped up on an easel. Let’s say it’s a portrait of the Madonna with child. Take a step closer and observe the rich, glowing reds and golds of her robes, the composition’s clearly rendered contours and forms.

Now fast-forward a couple hundred years. The paint is faded, discolored, maybe flaking. Details, once sharp, blend into the background, and the magnificently hued folds of fabric have turned dull. The artist has long since died and so has any viewer who saw it in its original form; chances are that little, if any, documentation exists.

That’s the dilemma that museums and art conservators all over the world face. How can they restore the work? How can they know the artist’s original intentions? What materials were used in the first place? How will those materials react to conservation attempts? This dilemma applies not only to paintings, but also to artworks created in virtually every medium. In fact, the minute any artwork is completed it begins to decay.

Thanks to recent advances in technology, art conservation is a science whose time has come. Conservators are learning more and more about historical art materials, noninvasive techniques, and how to best preserve and eventually restore artworks. Art conservation has drawn Weinberg students and scientists alike, who contribute to this exciting field poised at the intersection of fine art and science.

It was art conservation that led senior Alessa Gambardella, an Integrated Science and chemistry major, to an experience she’ll always treasure. She spent ten weeks last summer working as an art conservation intern at the world-renowned Metropolitan Museum of Art in Manhattan. While she was there, Gambardella worked in the Met’s scientific research department and rubbed shoulders with some of the museum world’s most accomplished professionals.

Before the start of the internship Gambardella participated in an intensive two-week orientation, during which she and her fellow interns were introduced to every curatorial department at the Met. They also took part in discussions with different museum administrators, including the director.

“It was great to hear that everybody loved what they did, and you could tell that they were telling the truth,” Gambardella recalls. “To become familiar with the inner workings of such a large non-profit organization is very fascinating—it amazed me how many people were involved in keeping it running and what a huge task it is.

“It was such a fun and rewarding experience to be able to apply what I’d learned at Northwestern, to expand my knowledge of how science is applied in the field of art, and to be surrounded by a whole department of people sharing the same goal of studying and preserving pieces of art history,” she continues.

For example, Gambardella learned how one Met conservation scientist developed a technique for preserving tapestries and other textiles that are vulnerable to attack by insects. Called “anoxic treatment,” the method involves placing the textile in an airtight bag into which argon gas is pumped; the gas kills off a variety of insects and fungi.

As part of her internship Gambardella gave museum tours and worked at the information desk, but spent most of her time in the lab. There she worked up a chemical fingerprint for synthetic dyes similar to those used in a particular tapestry in the Met’s collection. In the process she discovered information about the work’s provenance that conservators may later use to restore the tapestry.

Gambardella explains that she studied dyes, not pigments, which are a mixture of dyes and other substances such as oil. Dyes consist only of color molecules and can be either synthetic or come from natural sources, such as plants and insects. Scientists first copied colors from nature to create synthetic dyes in the 1800s.

“One great thing about knowing this is that you can date a work when you see that it was made before or after the invention of synthetic dyes,” Gambardella says. “You can tell what century it’s from and what particular region based on certain plants used in the dye.”

At the Met and in her ongoing research at Northwestern, Gambardella works with an analytical technique called surface enhanced Raman spectroscopy (SERS), which uses laser light to interact with molecules to show the chemical make-up of a particular dye. Raman spectroscopy, of which SERS is a more recent variation, is a widely used technique first developed in the 1920s.

In SERS the dye sample is placed in a solution of silver or gold, which makes the Raman spectroscopy more sensitive and therefore more effective. SERS has proved helpful in analyzing organic dyestuffs, especially red dyes, which are easily damaged by light or x-rays.

Gambardella learned about SERS from the master: Weinberg chemistry professor Richard Van Duyne, who pioneered the technique in 1977. Van Duyne also steered Gambardella to the Met’s internship, having recommended her to the Met’s director while they were both attending a conference in Japan last year.

“I told him how terrific Alessa was,” says Van Duyne, adding that as far as he knows she is the first person from Northwestern to complete the Met’s art conservation internship.

About five years ago Van Duyne joined forces with Francesca Casadio, a conservation scientist working at the Art Institute of Chicago, to implement SERS in art conservation. Graduate student Alyson Whitney joined them in their groundbreaking approach, and Gambardella started working with them two years ago.

What sets the SERS technique apart is its ability to analyze organic dyes, which were used to color all artworks created before the 1800s. That’s a lot of art—from cave paintings to Egyptian frescoes to Renaissance tapestries to English portraits and beyond.

According to Van Duyne, “Our research provides an entirely new window onto the analysis of artworks. There’s a broad range of physical science methods used in the conservation business. The trick is you can’t harm the work—the method has to be non-destructive or minimally destructive. Conservators do a lot of work with X-ray photography and infrared photography, but those techniques don’t tell you what elements are present. The Raman technique tells you about what molecules are there.”

In 2006 Van Duyne, Casadio and Whitney won the silver prize in the annual L’Oreal Art and Science of Color competition that, according to its Web site, recognizes “work that has successfully achieved a fresh and original meeting between science and art in color,” for their analysis of organic dyes.

The team is currently working on a project involving a watercolor painting by Winslow Homer titled "For To Be a Farmer’s Boy". The Art Institute is planning a major Homer exhibition in spring 2008 that includes the work, but conservators discovered that the painting’s white skies were originally painted in unstable red and orange dyes that have almost completely faded. Van Duyne’s team is working with SERS to discern the painting’s original colors in time for the exhibition. To do so, they must figure out a reliable way of preparing microscopic watercolor samples for SERS analysis. In the end, Art Institute conservators won’t repaint the original skies, but hope to offer a digital image that would give viewers an idea of the artist’s intentions.

Van Duyne says that conservation scientists are just beginning to unlock the secrets of dye and pigment analysis, and that in the future such analysis will help conservators determine forgery, authenticity, exact provenance and best restoration methods. “If we have a better idea about which materials are used in paintings, for instance, we’ll have a better idea of how to restore them. Just identifying what’s involved is a very important step.”

While Gambardella, Van Duyne, and his team of conservation scientists combine art and science in the lab, Frederick Northrup, a senior lecturer in physical chemistry, combines them in the classroom. In winter 2007 he began offering the freshman seminar “Chemistry and Art: Color, Forgery, and Effects on Society” and reports enthusiastic responses from students.

“The seminar brings the humanities and sciences together, which is good, because there’s a tendency for students to think they don’t have anything in common,” Northrup says.

He says that the seminar draws a diversity of students, roughly 60 percent of whom will probably be science majors and 40 percent from the humanities. He gives freshmen a list of possible topics for discussion that includes color, the chemistry of paint pigments, the effects of pigments on economies and the influence of the art world on the chemical industry, just to name a few.

Northrup came up with the idea for the seminar after he began working as a consultant analyzing clients’ house paints to determine lead content. He learned that the spectroscopic and other analytical tools he was teaching to chemists for other purposes were being used extensively for analysis of art works.

The seminar students surprised him. “Even with all the reading, discussion and writing that the seminar involves, the students really want to go into the lab. And it’s always the humanities majors who want to go into the lab to create pigment the most. They are thrilled to discover that you can take several chemicals and make a color.”

Northrup says that while he knows little about art, teaching the seminar has increased his appreciation for it and has filled him with wonder about art conservation’s ability to cross disciplinary boundaries. “This field shows important applications of science to areas like art, where people have thought that science had no place.”

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