Conservator Mark MacKenzie
THE Stewart L. Udall Center for Museum Resources is only 14 years old, but it can be mazelike. In the midst of one of its warrens is the former storage room that Mark MacKenzie calls his Fortress of Solitude. This is where he has his multispectral imaging laboratory.
MacKenzie, who has been the Museum of New Mexico’s chief conservator for the past 12 years, designed (with some help) and built the equipment he uses to carry out pioneering investigations of two renowned Segesser Hide paintings. “This was a sixmonth project that turned into two years,” he said. “These hides are really quite important. They’re the earliest extant representations of military expeditions within the geographic United States, from the early 1700s.”
The Segesser I painting depicts a conflict between rival tribesmen, possibly in the El Paso area. In Segesser II, we view a successful ambush by Pawnee and Oto Indians of Spanish troops who were dispatched from Santa Fe to Nebraska. The paintings’ substrate was believed to be bison hide. “I was able to confirm that,” MacKenzie said. “I worked with a bioarchaeology team at the University of York in the UK, using a new technique they developed for examining parchment.”
As chief of the Museum Resources Division’s conservation unit, MacKenzie has many responsibilities. He recently used X-ray fluorescence and a Geiger counter to assess potential repatriation materials for the Pueblo of Acoma, and his unit is at work on a remodel of the Museum of Indian Arts and Culture’s Here, Now & Always exhibition. But his Segesser project is undeniably significant and intriguing. His collaborators have included Eric Hansen, former chief conservator at the Library of Congress, and Hansen’s successor, Fenella France.
Among other talents, MacKenzie is an inventor. He worked with a camera-system designer and a company that makes automated plasma welding tables to construct a computer-controlled traveling imaging gantry. It’s a massive metal framework that incorporates a large platform with a vacuum table used to secure a painting, and above that, a motorized bridge. On the bridge is a high-resolution digital camera made by Phase One. Using a computer, MacKenzie directs the bridge to move in precise increments over the platform; the camera moves from side to side.
The “multispectral” part of the imaging equation relies on a set of lights on the bridge. “We use very, very special light to take pictures in a dark room, starting with ultraviolet, then five slices of the visible spectrum, then five slices of the infrared spectrum. We wind up with a stack of 19 images that reveal different aspects of the paintings. It’s absolutely amazing. I can actually see brushstrokes with this equipment. I was able to see through the paint, see down to the underdrawings.” Those drawings, used as guidance by the artist (or artists), have never been seen before, he said.
The hide murals are 54 inches by 18 feet. MacKenzie divided them up into photographed “tiles” of 9½ by 11 inches, resulting in hundreds of rectangular images of sections of the Segessers — totaling about two terabytes of invaluable digital information. “What I tried to do was not only answer questions but create a data set that can be mined by researchers into the future.”
The enthusiastic inventor brought out a prototype handheld meter that measures and displays ambient temperature, humidity, and ultraviolet light — readable in lumens and lux. “It calculates all the information that conservators love when they’re trying to determine whether displaying an artifact will damage it,” MacKenzie said. He is also an experienced wet-plate photographer who is looking forward to holding workshops using his collection of 8x10 view cameras. His career includes stints as a conservation chief for Parks Canada, Winnipeg, from 1981 to 1991; then as a head conservator of the Western Development Museum in Saskatchewan Province from 1994 to 2006. “Every 10 or 12 years, I move. January will be 12 for me, and I’m leaving this coming year,” he announced. He and his wife, Janet MacKenzie, who is the chief archaeologist with the Mesa Prieta Petroglyph Project, are planning to retire to Canada.
In concluding his discussion about the Segesser work, he emphasized that his detailed investigation was begun at the insistence of Josef Díaz, former curator of Spanish colonial art at the New Mexico History Museum. MacKenzie added that his multispectral imaging equipment was funded in large part by a bequest (shared with the Office of Archaeological Studies) from Don Pierce, who was a pathologist with a lifelong interest in Native American art, culture, and the landscapes of the West. A critical goal of the Segesser project is the ability to detect changes in the works and better preserve them. “These paintings are on skin, and collagen ages to a stiff, crinkly texture. We’re trying to assess where these paintings are on the curve of aging,” MacKenzie said.
Equally important is developing new information about their creation. “We didn’t really know much about the pigments and media, how these paintings were actually constructed. The blue paint should have faded by now, after nearly 300 years. Many people thought it was Prussian blue, which is considered to be the first synthetic color developed, in about 1705. But I proved them wrong. This is an indigobased blue, but it should have faded. I’m on the way to proving that this is Maya blue. The Maya had figured out how to marry indigo with attapulgite clay to make a synthetic blue, much earlier than 1705.”
MacKenzie’s study of the newly revealed brushstrokes has convinced him that there’s “a good likelihood” that there were Native American artists involved in the finalization of the artworks. A visit by representatives of the Pawnee Nation strengthened that belief. “This is the oldest pictorial representation of their people, and they were amazed at the accuracy of the painted figures and their regalia from what they have been told. I believe someone who was present at that battle was intimately involved with the design of the Segesser II painting.” — Paul Weideman
“These paintings are on skin, and collagen ages to a stiff, crinkly texture. We’re trying to assess where these paintings are on the curve of aging.”