Treasures of Biloxi: Art Conservation in the Wake of Hurricane Katrina

With their knowledge of the history of European painting, the conservators had some idea of what to expect from the results of the XRF spectroscopy. Analysis was done on the red, blue, and green areas of La Bella, the predominant colors in the figure's robe. All of the colors showed evidence of lead, which was used in white primer coats of paint before titanium white was first marketed in the 1920s. Having found lead in the primer coat, conservators could date the painting to a range from the 1500s to 1870, when it was purchased.

There were several possible types of pigment that conservators might find in the red paint. Starting in the 14th century European painters often used mercury-rich vermilion for pigment, and many painters still use vermilion today. In the 1500s organic red pigments made from ground female cochineal beetles came to Europe from the Americas. This red color results from carminic acid, produced by the beetles as a protective substance. Chromium red was first used in the early 1800s. Since La Bella was bought in 1870, the conservators were able to rule out the possibility of detecting cadmium, which painters began using in the 1920s. In the final analysis the red pigment showed mercury, and so the conservators were able to identify vermilion red. But since vermilion red has been used continually since the 1300s, the red was not helpful in narrowing the date of the painting.

In analyzing the blue paint the conservators saw many possibilities for further clues. Cobalt chloride is found in smalt, a pigment used from 1475 to 1825, made of ground ancient glass. The expensive and luxurious ground lapis lazuli, a complex compound of soda, silica, alumina, and sulfur, was favored in the Renaissance, and it was often saved by painters only for the robe of the Madonna. In their contracts with artists Renaissance patrons would sometimes show off their wealth by specifying the amount of blue to put into paintings. Today true lapis lazuli is still the most expensive blue pigment, although synthetic ultramarine, introduced in 1894, is chemically identical and much cheaper. Prussian blue, containing iron, was first used around 1700, and cobalt blue, containing cobalt oxide and aluminum oxide, came into use in about 1802. In the late 1800s painters began using cerulean blue, made of cobalt stannate. The XRF spectroscopy of the blue revealed only cobalt, frustrating the conservators, as some form of cobalt appears in most blue pigments other than ultramarine.

With little to help them narrow the date down from a near 400-year range, conservators turned to the green paint for better clues. Malachite, a copper carbonate, was used as a green pigment from ancient times until the early 1800s. The use of verdigris, a copper acetate, began during the Roman empire but completely died out by the early 1900s. Highly poisonous emerald green was used starting in 1814 and contains copper and arsenic. In the mid-1800s painters began using chromium in various green pigments, including chromium green and viridian, or chromium oxide dihydrate. The XRF examination of the green showed chromium, which proved that La Bella had been painted no earlier than the mid 1800s—around the time that Mrs. Davis purchased the painting. Lauren Cox, a WUDPAC graduate student conservator, speculated that Mrs. Davis probably saw the original 16th-century La Bella while in Europe, and it reminded her so much of Winnie that she commissioned a copy.

Once the mystery was solved, conservation of the painting could begin. The New Orleans Conservation Guild's work a year before Katrina had helped La Bella maintain much of its integrity through the storm. Although the bottom portion of the painting had been under water for several hours and there was a small puncture to the canvas, La Bella's paint loss and canvas damage were minimal compared with that found in the portraits of Winnie and Davis. As with the two other paintings, conservators cleaned La Bella, removed previous restoration efforts, restretched the canvas, revarnished, and restored areas of paint loss. La Bella now looks like it just emerged from the artist's studio, which, in a way, it has.

The library and mansion at Beauvoir are scheduled to reopen to the public in the summer of 2008. Artifact search and recovery on the estate is completed, and 3,814 artifacts have been photographed, inventoried, and stored. Much has yet to be done at Beauvoir before the salvaged collection can return to its rightful place. Stabilization, construction, and restoration of the two buildings are set to be completed in the spring of 2008. However, when the estate reopens, the paintings of Jefferson Davis, his daughter Winnie, and La Bella will be hanging in their original spots, looking like new. With the tool of chemistry at the center of some of their most important work, the conservators on the Winterthur estate have made an important contribution to preserving the historical heritage of the United States.