Unlocking the secrets of time, through tree rings

dmenconi@newsobserver.comNovember 9, 2013 

— Most people look at paintings from the front, but not dendrochronologist Tomasz Wazny. He focuses on the sides of works painted on wood, which reveal clues about when, where and how a painting came to be.

“I concentrate only on that section, the cross-cut edge,” Wazny said, pointing at the edge of a painting. “Using the width of tree rings, I can date the wooden panel and possibly the origin of the timber, maybe even its time of transportation.”

Wazny specializes in tree-ring dating. Between teaching and field work, he does several “house calls” a year at museums. He was at the N.C. Museum of Art in Raleigh this past week to determine the age of 23 paintings from the museum’s Northern Renaissance collection.

One was a 15th-century piece, “Christ and the Woman of Samaria,” painted on a thick oak plank by an unknown artist of German origin. Wazny propped up the painting’s edge on a piece of foam and gave a few pointers on the process, which starts with using a magnifying glass to examine, measure and count the textured tree rings visible on the cross-cut edge.

“This is a typical German painting, but to have it on a wooden support this thick is not so typical,” he said. “The crucial information is when this tree was cut, which will of course give information about the earliest possible date of creating the painting.”

If all goes well, Wazny ought to be able to narrow the wood’s “fell date” down to a year and even a season based on its tree rings. That can be crucial data when it comes to authenticating paintings as the work of a particular artist.

Each painting costs several hundred dollars to date, with this job at the N.C. Museum of Art funded by the Mellon Endowment. Noelle Ocon, a conservator at the museum, recalls that on a previous visit Wazny helped confirm that a 17th-century painting called “The Armorer’s Shop” was actually two different paintings glued together. They were even painted by two different artists, 20 years apart.

Some years back, Wazny also debunked a couple of supposed Rembrandts. It turned out that the wood they were painted on was not harvested until decades after the painter’s death in 1669.

“The owner thought he had some lost Rembrandt paintings,” Wazny said. “But in reality, they were 30 or 40 years too late.”

Wazny sometimes gets relevant data from the backs of paintings, where the wood might bear evidence of woodworking tools or trademarks from timber merchants.

But most of his information comes from painstakingly measuring hundreds of tree rings (most a millimeter or so in width) and crunching the numbers.

Dendrochronology is a family business for Wazny, whose father was a professor of wood and forest pathology in their native Poland.

The younger Wazny often went along when his father worked in the forest, and he moved in that direction himself. Dendrochronology was something he discovered while a student, and he was fascinated by how much information could be gleaned from counting and measuring tree rings.

That was three decades ago, when dendrochronology was an incredibly laborious process that involved graphing tree-ring data by hand on transparent paper and viewing it on light tables.

Nowadays, it’s all on computer – except, of course, for the students Wazny teaches in Poland and at the University of Arizona.

“It’s bad for my students, but I ask them to start this way,” Wazny said. “Graphing by hand and taking it to the light table is time-consuming but still the best way to learn dendrochronology.”

Once you have a set of tree-ring measurements, you plug them into software that compares the numbers to pre-existing databases of tree-ring chronologies. Depending on which data curves match up, you can narrow down the era and location of a given piece of wood. (It should come as no surprise that Wazny’s laptop computer has cartoon sketches of trees as a screen-saver.)

“To get results, you need to have chronologies of typical trees growing in a particular region,” Wazny said, entering measurements from “Christ and the Woman of Samaria” into his computer for comparative purposes. “Different wood species have different patterns – oak, pine, spruce, firs. This one is oak from the northwestern part of Germany.”

Even with computers, it’s not fast work. These chronological databases take years, not months, to assemble. But the more tree chronologies enter the database, the more precise dendrochronology becomes.

“Dendrochronology and conservation both take a lot of patience,” said Ocon. “Counting rings can be like watching paint dry. Yeah, it’s more interesting. But just as time-consuming.”

Menconi: 919-829-4759 or blogs.newsobserver.com/onthebeat

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