Last month, on her first day of work as the chief operating officer of Emmaus Services for the Aging, Nancy Piness took possession of an unlikely piece of the organization’s endowment: dirty, calcified pennies—enough to fill two buckets and a 12-inch by 12-inch plastic bag.

“I said, ‘What is this?’” Piness says. “[The pennies] are gross. They literally look like they came from the bottom of the Titanic.”

The coins’ history may not have gone back that far. But they weren’t exactly new to the 32-year-old seniors’ service organization. At some point in the distant past, an Emmaus staffer wrangled the pennies as a charitable donation from a property management company that was cleaning out a fountain in one of its buildings. No one presently on staff at Emmaus was around when the pennies arrived; the agency doesn’t have records indicating which fountain, or which property manager, was the source of the bounty.

“I’ve been with Emmaus for four years, and they were here when I got here,” says Rev. Joseph K. Williams, Emmaus’ executive director. “And here I am four years later, still trying to figure out what to do with these coins.”

It’s not for lack of trying. As a nonprofit, Emmaus wants to tap every source of income it can—including fountains where passers-by make wishes by throwing pennies. But turning those pennies into dollar bills turns out to be tricky. When staffers tried depositing the pennies at their banking institution (Williams declines to say which one), they were told that the pennies had to be cleaned and rolled.

How to do so? In this age of free coin-counting machines in bank lobbies, the counting should have been easy enough. But the detritus of all that time underwater meant the pennies confounded the technology. “The machines spit them out,” Williams says. “It jams the machines up.”

Instead, a staff member told Williams, he needed to take the pennies to the U.S. Mint—in Philadelphia. “That seemed to be a bit cumbersome,” he says.

So the minister tried employing volunteers to clean the pennies. “The methodology that they were using didn’t seem to work,” he says.

Williams can’t recall just what the methodology was. Basic chemistry explains the likely culprit: Calcium. The harder the water, the more calcium it has, and the more likely it is to leave deposits on surfaces, says Leopold May, professor emeritus of chemistry at Catholic University. “The calcium will fall down on to any surface that it can,” he says. “If you have a glass cup filled with water and you see white residue after you empty it, that’s calcium.”

As a newcomer, though, Piness says she’s determined to get full value from the forgotten donation. She speculates the change could add up to a couple hundred dollars. “We can’t afford to throw that away,” she says.

Piness, a Cleveland Park resident, took the nonprofit’s quandary to her neighborhood Yahoo! message board, in what she calls the “most bizarre question” she’s asked of the listserv community. She received more than a dozen responses, most of which involved applying some sort of acid to the pennies. Some of the suggestions include sprinkling salt on the coins and then soaking them in vinegar; soaking the pennies in a mixture of vinegar and lemon juice; soaking the pennies in muriatic acid; and soaking the pennies in Coke.

Suggestions in hand, the nonprofit now plans its own volunteer-driven science project to figure out which approach will leave the coins in fully redeemable form. Williams plans to have volunteers test the suggestions a handful of pennies at a time. “We’re going to see what will work,” he says.

In a fountain-laden city like Washington, Emmaus’ penny problems raise an interesting question: What happens to all that coinage that gets tossed into the District’s various pools of water. Piness’ buckets may add up to small change, but a tourist favorite like Rome’s Trevi Fountain can yield some $4,000 a day. (The Roman coins are collected each evening and given to charity).

The Market Square fountain in Alexandria yields about $20 a year in pennies, says the city’s deputy director of general services, Jeremy McPike. After the fountain’s semiannual cleanings, the city gives the coins to a local vocational center, where they are used for counting exercises.

Alas, the District’s fountain-keepers aren’t so generous, at least according to the National Park Service, which operates scores of them. According to spokesman Bill Line, NPS discourages penny-tossing, and passers-by mainly oblige. “Take the World War II Memorial, for example,” he says. “When it first opened in April of 2004, we got people throwing change. Shortly after, in May, we put up a sign saying something to the effect of, ‘Do not throw coins into the fountain.’” Additionally, park rangers instruct visitors not to throw change in the memorials with fountains.

Given the potential boon from guests with spare change in their pockets and a wish in their hearts, why does the NPS discourage coin tossing? “It clogs up the filters and pumps and costs the American taxpayers dollars,” Line says.

In the event that people do slip by the watchful eyes of park rangers and toss some change into an NPS fountain, the coins are unglamorously turned over to the agency’s comptroller and deposited in the U.S. national treasury. “It’s not a lot of money,” Line says.

Not by the standards of the federal budget, anyway. Back at Emmaus, though, the higher-ups would be happy with even a modest little haul.

In the event that vinegar and Coke don’t get the pennies clean, there’s always the option of switching banks. According to Beystan Kwlku, acting manager at Wachovia’s Adams Morgan branch, filth is no object: “As to whether it’s dirty, I don’t think it really matters.” Alas, the money still has to be rolled, Kwlku says. But that’s an activity a nonprofit’s corps of volunteers can tackle without an amateur chemistry set.