Corrosive Gas Restores Artwork, Promises Myriad Applications
- Monday, 07 April 2008
Short wavelength solar radiation in the space environment just outside of the Earth’s atmosphere produces atomic oxygen. This gas reacts with spacecraft polymers, causing gradual oxidative thinning of the protective layers of orbiting objects, like satellites and the International Space Station, which maintain low-Earth orbit directly in the area where the corrosive gas is most present.
To combat this destructive gas, NASA engineers developed long-duration coatings that are resistant to the effects of its problematic presence. To validate the effectiveness of the coatings, NASA had two options: Either send the materials into orbit for testing, which would involve the cost of launches and severely limit access to the experiments, or recreate the atmospheric conditions here on Earth. NASA chose the latter, and the Electro-Physics Branch at Glenn Research Center constructed ground facilities to test the durability of different materials by introducing them to a recreated form of the corrosive space gas.
The experiments were successful, and the coatings are currently used on the International Space Station. In the experimentation, though, the scientists discovered several additional interesting applications for their test facilities and beneficial uses for atomic oxygen here on Earth.
Led by Glenn’s Bruce Banks and Sharon Rutledge, the Electro-Physics researchers became familiar with atomic oxygen’s unique characteristic of oxidizing hydrogen, carbon, and hydrocarbon polymers at surface levels. While destructive to spacecraft polymers constructed with those materials, atomic oxygen’s selectivity could, they realized, also be applied in instances where someone wanted just those elements removed. Over the past few years since they made this realization, Banks and his team have partnered with several churches and museums to restore fire-damaged or vandalized artworks, and with an international forensics organization to develop new methods for detecting forged documents, as well as having developed a method for using atomic oxygen to remove bacterial contaminants from surgical implants.
Atomic oxygen is able to remove organic compounds high in carbon (mostly soot) from fire-damaged artworks without causing a shift in the paint color. It was first tested on oil paintings. In 1989, an arson fire at St. Alban Episcopal Church, in Cleveland, nearly destroyed a painting of Mary Magdalene. Although the paint was blistered and charred, after 230 hours of atomic oxygen treatment and a reapplication of varnish, it was once again recognizable as a work of art. In 2002, a fire at St. Stanislaus Church, again in Cleveland, left two paintings with soot damage that the atomic oxygen process was able to remove.
Buoyed by the successes with oil paints, the team also applied the restoration technique to acrylics, watercolors, and ink. As long as the paints were primarily synthetic, the results were promising. They discovered though, that some organic acrylics and ink, in particular, required less exposure so that the atomic oxygen would not begin to wear away at the medium itself. This potential liability has been used advantageously, however, in instances of graffiti removal. Experiments showed that, by using a pencil-thin beam of atomic oxygen, the team was able to remove most inks except black permanent marker.
At Pittsburgh’s Carnegie Museum of Art, where an Andy Warhol painting, “Bathtub,” was kissed by a lipstick-wearing vandal, the technique successfully removed the offending pink mark with a portable atomic oxygen gun. The process lightened a spot of paint, but a conservator was easily able to match the spot, thus restoring the painting.