The conservation of the Portrait of Godefroi-Maurice de La Tour d’Auvergne (1641-1721) by Robert Nanteuil: a conversation with Vasarė Rastonis, Mellon Conservator for Special Collections at Columbia University Libraries Conservation Program

The Conservation of the Portrait of Godefroi-Maurice de La Tour d’Auvergne (1641-1721) by Robert Nanteuil: A Conversation with Vasarė Rastonis, Mellon Conservator for Special Collections at Columbia University Libraries Conservation Program

In conjunction with the exhibition Art in Life: Engravings by Robert Nanteuil (c. 1623-1678) from the Frederick Paul Keppel Collection, the Columbia University Libraries Conservation Program graciously undertook the careful conservation of Nanteuil’s Portrait of Godefroi-Maurice de La Tour d’Auvergne (1641-1721). With minimal but observable damage, this engraving, dating from 1657, was an excellent candidate for conservation work that would allow for a deeper understanding of the materials used by Nanteuil in 17th-century France.

Vasarė Rastonis, Mellon Conservator for Special Collections since 2006, conducted the conservation work on the portrait. Rastonis received her training at the North Bennett Street School in Boston before beginning her career at the Newberry Library in Chicago, eventually joining the staff at the Columbia University Libraries Conservation Program. The Program works with all the libraries affiliated with Columbia, conserving books and works on paper for various projects associated with the University.

Before beginning a conservation treatment, Rastonis researches the object at hand if she is unfamiliar with it. This introductory research provides her with a deeper connection with the object than just working on it at the physical level. In the present case, she researched both the artist, Robert Nanteuil, and the sitter, Godefroi-Maurice de La Tour d’Auvergne, prior to starting the conservation work.

Rastonis explained that the first step in the conservation of any piece is developing a Treatment Plan with the team of conservators, which determines the conservation procedure. “None of these decisions are taken individually,” she said. For the Portrait of Godefroi-Maurice de La Tour d’Auvergne, the team discussed various treatment options. Determining how to approach the conservation of the object can often take more time than executing the work, Rastonis noted. Eventually, it was decided not to clean the engraving for it only had mild foxing (a reddish-brown staining caused by age and chemical deterioration) and cockling (a puckering or bulging of the paper) which may have occurred during production. However, it was decided to repair the top corners of the mount, as they showed significant loss.  Fortunately, the damage was on the edges of the mount and not on the part of the paper that was printed (Figs. 1, 2 and 3).

Rastonis began treatment by making stencils from two to three layers of Mylar™ – a thick, polyester film. She made these stencils by tracing the uneven border of the loss area and cutting the Mylar slightly larger to make it easier to handle during the repair. Rastonis used the stencils as working models in order to approximate the size and shape of the finished fills. She worked on the verso of the engraving in order to minimize the visibility of the repair work.

Next, Rastonis selected the paper to be used as filler for the missing corners. She settled on two layers of Japanese Sekishu paper and one layer of Western wove paper, known as Ruscombe Millshandmade paper (Figs. 4 and 5). She then toned the layers of Japanese paper in dye baths of acrylic color and de-ionized water in order to match the tones of the mount as closely as possible. Indeed, the tone of the mount’s outer band appeared markedly different from the tone of the mount’s inner band. According to Rastonis, a window mat was likely placed over the mount, such that the window covered the outer band of themount sheet, while its inner band remained exposed to light and air; light energy and particles in the air caused reactions  that changed the tone of the exposed mount over time. Matching the original tones was a precise, time-consuming process. According to Rastonis, “it is best to step away and come back to it” to get the colors just right. Rastonis created a “raw” tone for one layer and a “yellow” tone for the other. She left the Western paper in its original state, a creamy white color.

Once toned and dried, Rastonis adhered the layers of paper together. She used the Western wove paper, which is thicker than the Japanese paper, as a base to provide rigidity to the fill and to match the thickness of the engraving’s mount. She employed wheat starch paste as the adhesive, rather than methyl cellulose, which can also be used. She thinned the wheat starch paste into a slurry (i.e., a semi-liquid mixture) in order to decrease the strength of the adhesive, for a strong adhesive can pull the paper and cause it to warp. Rastonis took these steps to ensure that the adhesive can be removed at a later time, should conservation practices change. This is a standard principle in the conservation of works of art, known as “reversibility.”

Next, using the Mylar stencils, Rastonis cut the paper fill to match the shapes of the losses. To do so, she placed the paper fill on a plastic cutting board and used a variety of straight edges to shape it. She left the fiber ends of the fills long enough so that they would physically grasp the fiber ends of the mount paper. She then used a fine brush to apply the adhesive to the fiber ends of the fills and attached them to the mount (Figs. 6, 7, 8 and 9).  She manipulated the small-sized and delicate material with a metal micro-spatula and tweezers. In order to cut down the fills so that they aligned with the mat, Rastonis utilized an Olfa mini knife. She prevented the engraving from shifting during this process by placing on top of it a small glass square on a piece of felt (Figs. 10, 11 and 12).  Next Rastonis focused on the continuous black line at the perimeter of the mat. After testing many different Prismacolor colored pencils, Rastonis drew a thin but slightly irregular black line by hand, using a black Primacolor pencil and a straight-edge. She shaved down the pencil repeatedly to keep a sharp point (Figs. 13, 14 and 15). The team of conservators considered leaving the fill without the black line, since they prefer to not reproduce any of the artist’s work; however, they concluded that the fills were more obvious without the black line. As Rastonis explained, “we want the fills to be visible but we also want them to be subtle. The focus is the engraving.”

Throughout her work on the Portrait of Godefroi-Maurice de La Tour d’Auvergne, Rastonis photographed the engraving at various stages of conservation in order to document her process. This photographic documentation, including before, during, and after images accompanied by a color-balancing key, was included in the Treatment Report. The physical treatment of the engraving took approximately six hours over two days, not including the writing of the Treatment Report.

Vasarė Rastonis’ precise process of conservation provided a unique look into the living history of this 17th-century engraving. By treating the damage and explaining the treatment, Rastonis not only enhanced the print in anticipation of its display in the exhibition of Nanteuil’s engraved portraits, but also continued the print’s documented life.


Amy Hummerstone and Drew Lash