The vandal left inscrutable symbols — squiggly marks that in places looked like dollar signs — across the polished granite base of the statue in front of the Smithsonian's Castle.

The base stands at a height of about six feet, which makes it hard for passers-by to see, but preservationists approached the project carefully, testing for the right kind of solvent, according to Linda St. Thomas, a Smithsonian spokeswoman.

In the end, because that type of granite is not as porous as some stone surfaces, it was an easy cleaning job. The workers were taking a simple paint thinner to the figures Tuesday and expected to be finished by evening.

"It will be all over by the end of the day," she said.

At the Lincoln Memorial, National Park Service preservationists began their work just a few hours after two women out for a walk noticed the green paint on the Lincoln statue early Friday morning.

They closed the attraction down for 12 hours as they brought in high-pressure hoses, an approach that got rid of 90 percent of the paint by Saturday, said park service spokeswoman Carol Johnson. The toughest part has been removing a diagonal slash of paint from the marble base, a disfigurement still visible below the president's feet, she said.

Lee said it's possible that the area in question may have a rougher surface that makes it harder to clean.

For this area, the park service, having tested a variety of cleaners, chose MASONRE S-301, a cleaning product made by Cathedral Stone Products of Hanover.

"The way this material works is complicated," says Dennis Rude, the company's president, "but it actually penetrates the paint. When it reaches the substrate — in this case, the marble — it starts forming oxygen bubbles."

Those bubbles make it easier for workers to peel the paint off, he said.

On a stubborn job, Rude said, it can take several applications to complete the removal.

The Park Service crew had already applied the cleaner a few times and would do so a few more, Johnson said.

"We expect it to be completely removed within a few days," she said.

Johnson said it would be hard to estimate the project's cost yet, but in man-hours and materials alone it already is well into the thousands of dollars.

But the material damage seemed to be of less concern than the idea that someone would want to harm these attractions in the first place.

"This is one of the main things [my son] wanted to see," said Kim Jarvis, Austin's 40-year-old mother. "I can't believe somebody would do it."

On a warm, sunny Tuesday afternoon, tourists crowded into the Lincoln Memorial as always, snapping pictures on cameras hung from their necks — and straining to crop out the scaffolding.

A handful of park security officers wandered through the crowd. The restoration crew, some wearing bright green jump suits, worked silently.

Many tourists shook their heads at the scene but quickly added that the incident hadn't marred their experience.

At the National Cathedral, an Episcopal church Weinberg described as "the spiritual home of the nation," the Bethlehem Chapel on the basement level was closed to the public.

Tourists and worshipers could see into the Children's Chapel but could not enter. A ladder and a pair of lights mounted on tripods were still in the space near the high altar. There were only a handful of tourists nearby.

"We came to see the history, see the architecture – that's what it's all about," said Darlene Ortiz, a 52-year-old from New Mexico who was touring the cathedral with her husband.

Ortiz said they heard about the green paint before they arrived, but decided to come anyway.

"That wasn't going to keep us away," she said.

Jonathan Pitts reported from Baltimore and John Fritze reported from Washington.

The Washington Post contributed to this article.

jonathan.pitts@baltsun.com

john.fritze@baltsun.com