Caring for the Collections at Winterthur - Paintings Conservation

Here at Winterthur, paintings and other types of objects from our collection are cared for by a professional staff of conservators trained in craft, science, and history. We study how art and artifacts are made, how and why they deteriorate, and how best to repair and preserve them. My name is Mary McGinn, and I am responsible for the care of Winterthur's paintings collection. I would like to share with you a little about how paintings are made, how they age and deteriorate, and what we do as conservators to preserve these important cultural artifacts. How do we know how early paintings were made? Benjamin West's unfinished painting American Commissioners, usually on display in the DuPont dining room at Winterthur, provides valuable clues about the artist's process, from his initial sketch of John Adams' seated figure to the final highlights in the faces. Paintings are composed of layers. The layered structure may be as simple as paint on wood, but is typically more complex, often involving a piece of fabric stretched over a wooden frame, called a stretcher or strainer. A reconstruction of a detail from Joseph Badger's portrait of his son, Benjamin, illustrates the different layers of a typical 18th century painting. In this case, Badger used a gray ground or bottom layer to help him achieve cool shadows in the flesh. An artist would usually start with a sketch or underdrawing, here done in white chalk. The drawing could then be reinforced or embellished with paint. The painted image itself might consist of several layers, laid down by the artist in distinct stages, first blocking in the general form and color, then adding the subtleties of shadow, highlight, and detail. Prior to the late 19th century, artists would often coat or varnish a finished painting to protect the surface and make the colors appear richer and glossier. So why do these paintings look so different? After 250 years, paintings, like most objects, age and deteriorate. The layered nature of paintings contributes to their deterioration. As the environment changes from warm to cool, moist to dry, individual layers respond differently. This is a small sample of a painting that has been cut in cross-section and magnified 100 times. It illustrates the layered structure of a painting. As fibers in the fabric absorb moisture from the air, they swell. In contrast, if the air becomes too dry, the fabric shrinks. These changes in the dimension of the fabric cause paint to crack and flake. This pair of portraits, painted around 1840, hung in the same house for the past 70 years or more. The man's portrait hung on an exterior stone wall, while the painting of his wife hung on an interior plaster wall. As moisture migrated through the outside wall, causing swings in relative humidity, the paint layers of the man's portrait began to crack and flake. In contrast, the woman's portrait remained in fairly good condition. Such environmental fluctuations greatly impact the condition of paintings. Many of the works of art we see in these galleries originally hung in houses without central heat or air conditioning, and therefore developed cracks and other distortions. We can better see these cracks and surface imperfections by shining a light from one side in a technique called raking light. We have come to accept these imperfections as part of a painting's normal aging process. To minimize inevitable deterioration and prolong the life of an artwork, museums strive to keep their paintings in a controlled and constant environment. When cracked paint begins to separate from the canvas, treatment is necessary. Flaking paint, paint that has detached from the canvas, can usually be reattached by applying glue or adhesive beneath the flakes. In a process that resembles assembling a jigsaw puzzle, conservators use small brushes and tweezers to align the delicate flakes under a microscope. Sometimes a canvas is so damaged or weakened that it can no longer support its paint layers. This portrait of Jefferson Davis's daughter, Winnie, was damaged during Hurricane Katrina. The painting was so badly torn, it needed to be lined, a process in which a new support is attached to the back of the original canvas. This new support will hold the tear in plane and make the painting less susceptible to changes in humidity. Another change that we typically find with paintings as they age is a yellowing and darkening of the surface. Until the development of synthetic resins in the mid-20th century, artists coated their paintings with resins made from tree sap. These varnishes deteriorate fairly rapidly and predictably, becoming yellow and hazy over time. When a dirty and deteriorated varnish prevents us from seeing the artist's work, the painting can be cleaned and re-varnished. Removal of aged and yellow varnish can be controversial, especially if we might be removing an original varnish that was applied by the artist. But most artists were aware of the aging properties of natural resins and understood that their original varnish layer would eventually obscure the picture and require replacement. Today, if we remove a discolored coating, we typically re-varnish the painting with a modern synthetic resin that will not discolor and will be easier and safer to remove in the future. Although we may want to return paintings to their original state as they left the artist's studio, time leaves its mark and we have learned to accept and appreciate these signs of age, sometimes referred to as patina. As conservators, our goal is to first stabilize and preserve paintings in their current state and second, to present them in a way that is as true to the artist's intent as possible. We try, in a sense, to strike a balance between age and beauty. This portrait of William Washington Black came into the Winterthur Collection with its original varnish intact and it has never been lined. Should this painting be cleaned and lined to reverse some of the ravages of time? Or should we preserve it in its rare, untouched state? As conservators, we confront and debate such questions daily as we work to preserve not only the structure, but the aesthetic impact of the artwork under our care. In our efforts to strike that balance, we are guided by three fundamental principles. First, we strive for a better understanding of the science of materials and how they age. Second, we use stable materials that can be safely removed by future conservators. And third, we document the treatment process with photographs and with a written record of the materials and techniques used. Winterthur's conservation department trains tomorrow's practitioners through a master's degree program jointly sponsored with the University of Delaware. Our graduates work in the conservation departments of major museums throughout the world. The collections at Winterthur benefit from this collaboration as conservation staff employ cutting-edge techniques and use state-of-the-art analytical equipment to better understand and preserve Henry Francis DuPont's legacy.