“Madonna and Child With Saint Anthony Abbot and Saint Sigismund” arrived at the National Gallery of Art conservation lab 18 months ago with standard symptoms: darkened skin, lost pigment and damaged gilding. Most 500-year-olds suffer such complaints, so senior conservator Carol Christensen wasn’t alarmed.

Taking the patient’s history proved a greater challenge. The Renaissance altarpiece doesn’t turn up in the record books until about 1850, at a church in suburban Siena, Italy. Before that, total amnesia: No one knows who commissioned Sienese artist Neroccio de’ Landi to paint it in the late 15th century or where it first hung.

…The facelift began with a camera. Museum technicians shot about 100 close-up infrared reflectograms, as they’re called, and knit them into a monochromatic mosaic of the altarpiece. Now Christensen could see the first layers of drawing and under-painting laid down after Neroccio primed the surface. As she searched the lines and shadows beneath the Virgin, her son and the saints, the infrared images let slip a confidence: Neroccio, long believed the sole author of this work, wasn’t working alone.

Christensen points to the infrared of the squirming Christ Child and indicates the dark, brushy lines defining the boy’s pectorals and belly. Neroccio was regarded as a tentative draftsman who favored fine lines, she says, yet these are bravado strokes typical of Francesco di Giorgio, a longtime Neroccio collaborator who, she believes, almost certainly worked on this piece.

Then Christensen points to the blurry areas around the Virgin’s elongated hands. “You can see that Neroccio’s had some difficulty in deciding the contours of the fingers, so there are little minor changes there,” she says. In these murky scans, the artist’s process comes to life.

Christensen moves to a wall-mounted light box about the size of a craps table, where a series of X-radiographs have been taped up with blue adhesive. These scans map the entire work, showing every paint and support layer simultaneously.

Behind undulating lines of wood grain, a faint grid pattern covers the panel like a checked picnic blanket. Christensen identifies the grid as a cradle added in the 19th or early 20th century to reinforce the panel for travel to America, where it was feared that temperature extremes would warp the wood. Such supports often did more harm than good, and no conservator installs them now.

At the top, black lines mark where additions were made to the panel twice — first by Neroccio and again centuries later by someone who wanted to fit the canvas, with its angled upper corners, into a rectangular frame. No wonder the gilding, applied with a tiny punch, is so damaged; Christensen will summon the gallery’s gilder to fix it.

In these X-radiographs, paint layers appear as various densities of white. Black indicates no pigment at all. Christensen gestures to the floor tiles at the Virgin’s feet, which are a sea of black. There will be major in-painting to do.

A pair of black cracks down the length of the panel confirms Christensen’s suspicions. Three planks were joined to make this panel. Through the centuries they’ve been moving with fluctuations in temperature and humidity. Because joints move and paint doesn’t, pigment simply flakes off. There will be more in-painting and regilding ahead.

“Do you see this sort of shadow?” Christensen asks, pointing to the small orb in Saint Sigismund’s left hand. “The ball was originally bigger, and he decided for some reason to narrow it. You can feel him working out the whole process.”

So many choices. These images offer a history of the artist’s strategies, complete with hesitations, botched ideas and brilliant solutions.

(The Washington Post)