The other day when we asked “Where’s the Caillebotte?,” we explained that it was being x-rayed in the conservation lab and invited visitors to strike a pose with the frame—an invitation that was taken up by a few of our art handlers. But really, the extent of what was done in our lab was more complicated than that, so I thought I would expand on the process.
The first step was taking an x-ray, which requires a special set-up for such a large painting. Here in the lab the painting was placed face-up on long beams to hold it above the x-ray unit. It was measured and a grid of thin thread was pinned to the edges to help line up the sheets of film and avoid any gaps. The x-ray unit itself is inside a lead-lined box on wheels with a rectangular opening facing the painting. It allows the x-ray beam through the painting to expose the film, in a light-protective sheet on top. The small beige booth behind the painting at the center of this picture is where I manned the controls.
This little booth is leaded, as well as the glass, to protect the operator while the x-ray unit was energized (as indicated by the red light below). For each capture, a new x-ray film and protective sheet was placed on the grid, and the x-ray unit was rolled underneath to correspond with that space.
Here’s the view from where I stand during the process:
Each sheet of film was developed and placed on the big wall-sized light box in our examination room. Once we did some test shots to figure out our exposure settings, we developed the film in batches. Putting the film up like this is a bit like a puzzle, but it helped us see the overall picture and make sure we haven’t skipped anything. The grid we made also takes into account a certain amount of overlap between the films—seen here on the light box—which will help us when we scan and digitally composite them.
We also took the opportunity to take some infrared images of the painting in both reflected and transmitted light. In the infrared part of the light spectrum, the longer wavelengths penetrate the upper paint layers and we have the ability to see changes in the paint not visible on the surface, as well as some kinds of underdrawing. The camera is tethered to the computer so I can see the images as they are generated. Along with the x-ray, these images give us a better picture of Caillebotte’s working process.
Finally when our work is done, the installers placed the painting back in its frame on the gallery wall for your continued viewing pleasure. Stay tuned for the results of our technical imaging in conjunction with the Impressionism, Fashion, and Modernity exhibition.
—Kelly K., Andrew W. Mellon Fellow, Paintings Conservation