A painting is an image, but it is also an object. The image resides in a thin film of pigment bound by a medium, such as egg yolk or oil, to an underlying support: a taut piece of canvas or—in the case of many Western paintings before the late-15th century—a carefully prepared panel of wood.
For most of us, the painting is what we see on the surface, where light reflects the image into our eyes. George Bisacca ’77 sees that same image, but his vision of a painting penetrates more deeply, to the object beneath. As one of the world’s leading conservators of paintings on wood (often called “panel paintings”), Bisacca sees through the paint to the cracks, fissures, worm holes, and clumsy repairs of centuries past—yet he also sees the craftsmanship, history, cultural tradition, and immense beauty of these objects.
In the airy, north-facing conservation studio atop the Metropolitan Museum of Art in New York, Bisacca stands among a dozen paintings. Some need minor repairs, removal of yellowed varnish, cleaning, or minor retouching. Others are in shockingly bad condition.
On a nearby easel stands a large German oil on wood from about 1585, an Annunciation given to the Met last year by a Florentine art dealer. It’s a familiar Christian scene: the angel Gabriel gestures toward a demure Mary, each figure occupying about half the picture. And in the sky above, a bearded figure of God points at her, releasing a dove of peace.
The two halves of the composition are unified by sightlines and gestures—but they are no longer physically joined. The original panel, made of four planks of wood, has bowed and cracked along its three seams; the central seam is so badly compromised that Bisacca decided to separate it entirely. It seems like radical treatment, but now conservators will be able to align the surfaces and adjust the natural curvature of the entire panel. Once the pieces are rejoined, restorers will clean and retouch the damaged surface, being careful to use materials that can be removed later without damaging the original paint. Today’s restorations are largely done in this manner, so that future conservators can reverse this treatment and conserve the painting differently as new science emerges.
There’s a lot of science in modern art conservation. Soon after X-rays were invented, people began using them to investigate works of art, often finding surprises below the visible surface. Bisacca shows me an unfinished portrait of Michelangelo, painted about 1545, when the great artist would have been 70. It’s attributed to a devoted follower, Daniele da Volterra. Yet X-radiography clearly shows that Daniele painted his Michelangelo atop an earlier image of the Holy Family.
With its varnish removed, the portrait looks flat and faded. Bisacca takes a cotton ball, wets it with turpentine, and swipes it across the face of Michelangelo, bringing out the contrast and color, just as a fresh coat of varnish will do. He points to where the ghosts of the older composition can be seen in the unfinished areas, then shows me the back of the painting, which he and his structural team stabilized before the restorers began their work on the painted surface.
X-rays aren’t the only diagnostic tool in the hands of today’s conservators. Infrared reflectrography can reveal an artist’s preparatory drawing, showing how a composition evolves as the artist proceeds. Chemical analysis of paint reveals artists’ techniques and points the way to proper treatments of the surface. And not long ago, Bisacca used a CT scanner to solve a persistent mystery concerning an early Renaissance painting in the Met’s collection.
For a century, art collectors have been hunting down pieces of the Borgo San Sepolcro Altarpiece, painted in the late 1430s by the Sienese artist Sassetta. Like many altarpieces, it consisted of several separate paintings hinged or pinned together. Some were double-sided so that when the altarpiece was “closed,” additional images appeared on the back. Like many old altarpieces, the San Sepolcro was broken up and sold to multiple buyers; the two-sided panels were often sawn in half in cross-section, creating two paintings where there once was just one.
Three central elements of the San Sepolcro altarpiece were found in a Florentine antique shop about 1900 by the famed connoisseur Bernard Berenson, and the hunt has been on for the rest ever since. One supposed member of the set was thought to be in the Metropolitan’s Lehman Collection, yet doubts remained about its attribution.
The problem was that the Met’s painting appeared to be on cypress, while all of the other San Sepolcro candidates were on poplar—including the one thought to be the obverse of the Met painting, a Crucifixion owned by the Cleveland Museum. Met curators were thinking that sometime after the paintings were separated, a cypress backing was laminated to the Met’s thin poplar panel, but they couldn’t prove it. Cutting into its edges to investigate its composition was not an option; it would have been too destructive to the painting and its attached frame.
So, at the suggestion of a colleague, Bisacca took the 17-inch-wide panel downtown to New York University Medical Center, where the CT scanner saw exactly what had been expected all along: a lamination line between two layers of wood—cypress on poplar.
Another key piece of evidence was also found in the scan. The annular lines—tree rings—in the poplar portion of the Met’s painting matched exactly the rings visible on the back of the Cleveland piece. “That put it completely beyond doubt,” Bisacca says. “We proved it.”