For the first time since they were carved into a mountain in South Dakota, the 4 presidential portraits on Mt. Rushmore will be cleaned. The effort seeks to remove damaging lichen-type mosses and dirt that have accumulated on the sculpture. A German cleaning crew is leading the effort, and they're doing the job for free.

Thorsten Mowes has his feet planted firmly on Thomas Jefferson's chin. Secured by a harness that suspends him 18 meters in the air, he aims a high-pressure sprayer at the president's cheek.

Mr. Mowes and his colleagues are blasting near-boiling water at a pressure of about 30 bar onto the rock surface of Mt. Rushmore -- removing dirt, as well as the lichen that's grown on the presidential faces since they were carved more than 60 years ago. That's "the important part of doing this," according to park ranger Duane Buback, who says the cleaning will help preserve the monument. "The root systems [of the lichen] penetrate into the surface of the sculpture causing damage, opening up small spores. And what we're worried about is when we start getting moisture and that moisture freezes later in the year, we will end up having larger areas to patch. And so by removing that, we're removing the problem of the penetrating lichen."

Cleaning the massive faces of Rushmore is no easy task. The local fire department is helping out, laying out nearly ½ a kilometer of fire hose to carry water up 180 meters to an 11,000 liter holding tank near the top of the mountain. Meanwhile a network of nylon ropes is being put up each day so workers can lower themselves -- and their sprayers -- in front of the faces. And the Park Service is even getting some international aid.

Five gas-powered high-pressure sprayers have been helicoptered in -- and up -- and placed behind George Washington's head. They're manufactured by the Karcher Company of Germany, which specializes in high pressure cleaning equipment. The company is donating the use of these machines and trained personnel to use them? a contribution worth hundreds of thousands of dollars... but project leader Frank Schad says it's not about the money. "We don't just give money," he points out, "but we give our technology, our experience. You know it's something very personal, it's always people who are doing this. And we are doing things that others mostly or very often couldn't do, so sometimes we really rescue monuments which are in danger."

Indeed, this isn't the first monument the Karcher Company has cleaned. As he prepares to rappel down Thomas Jefferson's nose, sprayer in hand, Thorsten Mowes says the company has sent its equipment and personnel all over the world. "Over the last 20 years we have done now more than 80 projects all around the world, on every continent." He lists some of them. "The Jesus Christ statue in Rio de Janeiro, or the Brandenburg Gate in Berlin, the Statue of Liberty in New York, the Colonnades of Rome in Italy... the colossus of Memnon in Luxor, Egypt, for example, yeah."

Karcher Company officials say cleaning the world's monuments allows them to test their equipment on various surfaces and is a good way to promote their company. Mt. Rushmore officials say it's a good deal for them too. Not only are they getting the work done at no charge, Duane Buback says Karcher's water cleaning process will have little impact on the environment. "Compared to other proposals of chemical treatments, and sand blasting and media blasting, the pressure washing process is less invasive. It will take care of the surface without damaging the surface of the sculpture itself."

It will take 15 workers 4 to 5 weeks to clean these faces. So this summer, visitors -- looking up from the valley below Mount Rushmore -- will notice workers dangling from ropes, dwarfed by the huge faces. When this project is over, the average visitor won't notice much of a difference, but company officials say up close, the damaging lichen will be gone. And so will the Karcher crew. They'll be on to their next assignment: cleaning Beijing's Forbidden City, a task that is expected to take several years.