BRIDGTON (AP) – A Bridgton man has written a book about his bottle-digging adventures in dumps, on farmsteads and at other sites in search of glass relics from the past.

Walt Bannon’s book, “Digger Down,” includes 17 stories recounting expeditions by him and his bottle-digging partner, Walt Underwood. The book was picked up by PublishAmerica, a Maryland-based company that specializes in new authors and uses a print-on-demand method. Bannon says the book could be out in about six months.

Bannon, 50, and Underwood, who is 58, formed a group called Bridgton Old Bottles after they started digging in the Bridgton area a couple of years ago in search of glass from the past that what was once considered trash.

In looking for glass collectibles, the pair looks for old sites where people once unloaded wagonloads of junk. Their hobby is part archaeology, part history and part fun.

They have amassed hundreds of bottles, including clear milk bottles, ink wells in various colors, a cod liver oil bottle and little cobalt bottles with ribbed panels that signal they held poison. Their oldest bottle dates to about 1850.

The two plan to exhibit the best of their bottles at a show next month.

Around the country, it’s getting harder to find good sites to find old bottles, according to Reggie Lynch, a bottle dealer in Raleigh, N.C., who runs www.antiquebottles.com. Many spots dried up when the hobby became popular decades ago, he said.

“It got real hot in the ’60s and ’70s, and in the ’80s it kind of died down,” Lynch said. “They did the research, found out where all the old town dumps were and dug them all up.”

Bottle-collecting has picked up again since the early 1990s, Lynch said, but it’s more difficult to find good digging spots now.

Bannon and Underwood said the past year has been successful for them as they have searched gravel pits, basements, crawl spaces and other spots. Most expeditions yield some treasure, they said.

“These really are everywhere,” Bannon said. “It’s just knowing where.”