Putting the Shine Back into the Arch

A group of national nonprofit organizations and preservationists are researching methods the National Park Service can use to clean, and possibly refinish and conserve, the exterior of the St. Louis Arch, the St. Louis Post Dispatch reports.

The Arch has not been fully cleaned since shortly after its completion in the fall of 1965. At that time, final cleaning, repair, and polishing was done by hand in a process that lasted a full year.

More than 55 years later, dirt, grime, pollutants, and graffiti have taken their toll on the shiny, stainless steel surface. At the ground level, de-icing salt has caused superficial corrosion.

The Arch cleaning report put together by the nonprofits and preservationist suggests drones, lasers, and rappelling as means to reach the 630-foot monument’s surfaces. Possible cleaning methods include a combination of pressurized water, steam, and dry ice as well as manual polishing with chemical solutions.

The park service investigated Arch corrosion more than a decade ago and finished a report in 2006 on the issue. But in 2015, after further study and testing that featured people rappelling down sides of the Arch for the first time in its history to gather samples, park officials said it was “not feasible” to pursue a full cleaning of the structure.

But in 2018 several outside organizations, including the Los Angeles art preservation nonprofit, the Getty Foundation, and the Springfield, Illinois-based Association for Preservation Technology, started their own investigation into conserving the Arch. Their findings are in the report under consideration by the National Park Service.