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Soft-sponge Abrasive Helps Presidio Get Tough on Graffiti
Are damaged bricks repairable, or should they be replaced? Missing bricks do have to be replaced, but with what? Opinions differ on the merits of the options. by Jack Innis
“Leave no stone unturned” was the goal of conservators of the Presidio Trust when it came to finding a long-term method of dealing with graffiti on its historic sandstone-masonry Boundary Wall.
The Presidio Trust manages a portion of the former U.S. Army base known as The Presidio of San Francisco. According to the National Park Service Web site, the base has a rich cultural history, beginning with the native Ohlone people, the Spanish arrival in 1776, 24 years of Mexican rule, and finally U.S. Army control in 1846.
Since 1994, the Presidio has been a part of the Golden Gate National Recreation Area. Among the park’s most enduring features is the Presidio Boundary Wall, a five-mile-long, broken-range, ashlar-pattern sandstone wall along the Presidio’s south and east perimeter that was built in 1896 and is now a National Historic Landmark.
Lately, portions of the wall have been targeted by taggers. Although graffiti has been around a long time, it is a relatively recent occurrence on this wall. “There are a lot of areas in the Presidio that get graffiti, but we are able to take care of them more readily because they’re not on historic surfaces,” says Presidio Trust Senior Preservation Conservator Christina Wallace. “The Boundary Wall is sandstone, historic, and it’s fragile.”
Presidio Trust maintenance personnel — trained in masonry, conservation, and graffiti removal — have used chemical strippers on the sandstone in the past. But they wanted to explore whether new technology would allow cleaning with minimum effect on the substrate.
