In a secret back room of a San Francisco hotel wired with fiber optic cable, one man still practices a tradition leftover from the 1930s: cleaning money.

Rob Holsen is the coin washer at the Westin St. Francis Hotel, and perhaps the only coin washer on Earth.

He said the hotel on Union Square started washing its coins in 1934 when the general manager noticed a woman's white gloves getting dirty. Now, nearly 80 years later, the tradition somehow survives.

"I once gave an FBI agent my card that says 'coin washer' on it," Holsen said. "And I told her we laundered money, at which point she reached for her hip."

Most of the coins Holsen cleans come from the front desk and restaurants in the hotel. The washing process takes about seven hours.

First the coins are sorted by denomination, then a washing machine tumbles the coins around in a mixture of buckshot, soap and water.

"Basically you've made a meringue out of soap and water instead of egg whites," he said. "Then you have to put your hands in this black goo."

After the coins dry, Holsen rolls them and puts them back into circulation.

Holsen has been working at the hotel for 30 years. After 20 years as a coin washer, he thinks he has cleaned about $1.5 million in coins.

For security reasons, Holsen has to go through four different locks to get to the coin washing room. The last lock opens "the magic door with no writing on it," he said. Even most employees at the hotel don't know where the room is.

Although white gloves aren't as popular as they were in 1934, Holsen said it's a pleasusre carrying on the tradition.

"It's sort of like the cable cars," he said. "They don't really function in the 21st century, but they're still there and they're still a source of pride for the city."

Holsen also advises aspiring coin washers to forget about finding a job. "This is the only one there is in the world, so I have it and you're not going to get it."