DIGGING IN: I started out collecting coins. At about age 12 I got a metal detector, and I'd search to fill the gaps in my collection. One day the water-meter man saw some old bottles I'd come up with and said, "I know where there's a dump; you're welcome to come when I take another guy that's into bottle digging." So I started doing that. Now, my interest is in pre-1860s bottles.

THE GREAT CHASE: People collect bottles because they consider them folk art. There are niches -- medicine bottles, historical flasks, particular manufacturers. The biggest East Coast show is in March, outside of Baltimore. It's over 300 dealers. Millions of dollars' worth of bottles change hands. But for me, it's not about that; it's the hunt.

PRIVY DIVING: One of the best ways to find old bottles is to dig up old outhouses. Before the 1900s, people threw all their trash in there. The privy captured what somebody ate, purchased, threw away, lost. The first one I dug up, someone had dropped in a whole box of clay smoking pipes, about 40, all intact. Once it's sealed off it's not disturbed; it's like a time capsule. By the time we dig, all that's left is what doesn't biodegrade -- the rest is so old it's turned to soil, like compost.

GEOGRAPHICALLY CHALLENGED: D.C. isn't a great place to dig. In the 1830s they passed an ordinance requiring shallow privies, so most were above ground or just three feet deep. (In Philadelphia they might be 25 to 35 feet, or in Pittsburgh they can be 50.) The other thing is that all D.C. landfill is federal land -- the Mall, the Navy Yard. You can't dig there. Baltimore is better: It has more quasi-public land, and it had prolific bottlers.

BONANZAS: There are some good finds in D.C., though. I have a bottle embossed with "16th and U" -- there was a pre-Prohibition bar where Stetson's is now. Another is from near the MCI Center. A construction crew let me in. They'd cracked open an old cistern. The operator said, "Get in now; tomorrow first thing that's all gone." There's a tension between archaeologists and what they call "pot hunters" -- they say we mess up the sites. But what I find is about to be lost; once it's gone it disappears forever.

COLLECTING COMPULSION: Ted Botha just wrote a book ["Mongo: Adventures in Trash" (Bloomsbury, $24)] with a chapter on privy digging. He gets at people's predisposition to collect. I talked to a backhoe operator who works around the country. He said, "I like to get a bottle with the name on it from every city I go to." That's a labor of love.

As told to Sandy M. Fernandez

Just call him Dig Dug: Andy Goldfrank reaches up to show off a prize piece.