The New Detectives

Architectural conservators work as gumshoes to solve mysteries of old buildings.

An architectural conservator at work in the lab

Credit: Gary Henry, PROSOCO

Recently, officials in Alton, Ill., couldn't figure out what was defacing the exterior of the historic Youth Library, built in 1891. A peculiar white substance was appearing on the library's brick exterior. Authorities tried cleaning the brick, but to no avail. So they did what people do in mystery novels: They called a detective.

Enter Frances Gale, technical director at PROSOCO, a company in Lawrence, Kan., that specializes in preserving architectural surfaces. An authority on historic preservation and former training director of the National Park Service's National Center for Preservation Technology and Training, Gale is no stranger to pathology in historic structures.

In PROSOCO's basement laboratory, Gale and her staff spent weeks analyzing masonry samples from the library, conducting such tests as gas chromatography and x-ray diffraction. Working with Metropolitan Design and Building Company in St. Louis, near Alton, Gale hopes to eradicate the white substance and restore the brick's dark-red color.

So what is the mysterious white stuff? The final report isn't in yet, but it's likely salt. Not just one type of salt, but possibly several kinds have leached into the absorbent brick—"maybe a residue of an old attempt to clean the building," Gale says.

There are hundreds of testing labs across the country, but only about a dozen or so, including PROSOCO, employ technicians educated in historic preservation. Called architectural materials conservation specialists, these scientists can analyze and identify building materials yet are also educated in historic preservation and building conservation. Because the materials and building techniques of the past differ from modern methods, the lab and field work that these specialists do is key in remedying pathology in old buildings and in uncovering their histories.

Almost every problem facing an architectural conservator is a mystery, but some are more puzzling than others. Take, for example, the Case of Grand Central's White Walls.

New York's Grand Central Terminal was undergoing restoration in the 1990s when lead architects Beyer Blinder Belle asked a Manhattan-based firm of architectural conservators and preservation specialists, Integrated Conservation Resources (ICR), to work with them on a particularly spotty problem. ICR's task was to find a way to clean and restore the imitation Caen stone on the interior walls of the waiting room and main concourse at Grand Central. The craftsmen who fabricated the walls in the early 1900s had reproduced the reflective, golden-yellowish characteristics of genuine Caen stone, a type of limestone found in France.

But over the years soot, grime, and applied pigments gave the manmade stone a dirty checkerboard appearance. A beautification campaign in the 1980s expunged the checkerboard look, resulting in walls that were uniformly clean, almost white—at the expense of their original golden color. In fact, what the cleanup had done, says ICR president Glenn Boornazian, was "melt the surface of the imitation Caen stone." A paste that cleaners applied to the imitation stone, dried, and then brushed off also left behind tiny clay particles embedded in the wall's pores. 

History under the microscope

Credit: Gary Henry, PROSOCO

ICR workers examined the interior walls at Grand Central with microscopes, took samples back to their lab, and examined them under higher magnification, using x-ray diffraction to help identify the material. Their tests revealed that it was the clay particles that had bleached the imitation stone. Although the imitation stone was intact, further tests showed that cleaning the walls with water, or almost any liquid, would damage them.

"So there [was] the mystery," Boornazian says. "How can you come up with some sort of cleaning process that's non-destructive? That grabs the clay particles and gets them out without damaging the physical structure?" ICR ran cleaning tests for more than a month. "We involved people like PROSOCO, and they tried their own ideas," he says. "We got very imaginative and came up with things like potential vacuum systems. Believe me, so much was tried."

Then Boornazian had an inspiration. Perhaps liquid latex, which his staff had been using to make architectural molds, could safely be applied to the imitation stone. Sure enough, the ammonia-based latex could be painted on Grand Central's walls, allowed to dry, and then peeled off like putty, taking with it the dirt and clay particles, thus restoring the imitation Caen stone's gilded tint.

"We ended up using a product completely outside the field of preservation-conservation cleaning," Boornazian says. "And, in a way, that's what makes a good conservator. It's knowing what the material you're working with is made up of so you can choose potential methods that will not be destructive. And then being open to different possibilities." 

Portland's Abyssinian Church

Credit: Maine Preservation

While lab work and an encyclopedic knowledge of historic building materials are essential for solving mysteries in old buildings, they're often partnered with good old-fashioned sleuthing. Consider the Case of the Vanishing Meeting House.

Built c. 1826, the Abyssinian Church in Portland, Maine, is the third oldest African-American meeting house in the country. Before the Civil War, the wood-frame and clapboard building was both a school for black children and a stop for runaway slaves on the Underground Railroad. Decommissioned as a church in the 1910s, the building was converted to apartments.

By the 1990s, it was vacant and deteriorating, so the Committee to Restore the Abyssinian stepped in to rehabilitate the church and turn it into a museum. In 2000, the committee asked Building Conservation Associates' (BCA) team of preservationists and conservators to help.

"The building had been gutted, basically," says Andrea Gilmore, regional director of BCA in Dedham, Mass. "[But] we looked for evidence of any surviving historic building fabric."

BCA architectural conservator Brian Powell scoured historical records and found that the interior of the Abyssinian had been removed in 1916 and reused in another church elsewhere in Maine.

"So he went sleuthing to find it," Gilmore says. Powell's investigations led him to the small Mission Congregational Church in West Paris, Maine. By comparing paint layers, Powell found "pretty much the entire interior" of the Abyssinian Church incorporated into the Mission Congregational.

"How do you sleuth and find something that really is the Rosetta Stone that tells you the story of a building, when many of the elements appear to be missing, at least at first glance?" Gilmore asks. Laboratory analysis of fragments from the gutted building confirmed that, indeed, here in West Paris were the pews, wainscoting, and other pieces of the Abyssinian Church in Portland. "We found almost all of the interior finishes, not where we typically find them [in the original structure], but reused in another building."

The study of the building continues, Gilmore says, and restoration is pending. But it's a project she's confident will go forward. "Of the three [oldest] African meeting houses in New England," she says, "this is the one with the most original building fabric—though not presently in the building."

Is there a common thread that ties architectural conservators together? Many—including Gale, Boornazian, and Gilmore—did their graduate work in historic preservation at Columbia University. "Lots of us were trained in a pretty small number of graduate schools that specialize [in historic preservation]," says PROSOCO's Gale. (Both Columbia and the University of Pennsylvania offer such programs.) She adds with a laugh, "We're a small, kind of tight little mafia."

And they all seem to enjoy a puzzle. "It's one of the things I love about this profession," Gilmore says. "Certainly, we don't [solve mysteries] every day. But we do from time to time, and it's lots of fun."

Jane Lotter is a freelance writer living in Seattle.

This story was originally published on Preservation Online on Feb. 6, 2004.  

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