Sea glass is trash that the ocean has forgiven. That's Mike's line and he's proud of it, so I'll let him have it. More exactly: it's broken glass, mostly from bottles, that has been in the sea long enough for the waves and the sand and the salt water to wear the edges round and take the shine off the surface, leaving a soft, frosted pebble that looks like nothing so much as a piece of hard candy. You find it at the tide line, mixed in with the gravel and the shells, and once you've found one you cannot walk a beach again without looking down.

Where it comes from. Bottles, mainly: beer, soda, milk, medicine, wine, ink. Tableware and jars. Windows and lanterns from boats. In the days before trash pickup, people who lived by the shore threw their bottles off the rocks, and towns put their dumps at the water's edge, and ships tossed their empties over the side, and all of it broke and went into the tumbler. A beach with good sea glass is nearly always a beach that had a town, a cannery, a ferry landing or a summer colony near it fifty or a hundred years ago. That's why the old harbors are better than the wild stretches.

How long it takes. The rounding is mechanical: the piece rolls in the surf against sand and stone until the sharp edges are gone. The frosting is slower and it's chemistry: the salt water very slowly leaches the surface of the glass and leaves it pitted and cloudy. Between the two it takes a few decades at least, and the best pieces, thick, fully frosted, with the little crescent-shaped pits all over, have been in the water longer than either of us has been alive. A piece that's still shiny or still has an edge isn't done. Throw it back and let the sea finish it for whoever comes after you.

The other thing to know is that there will be less of it as the years go on. Bottles have been plastic for thirty years, the dumps have moved inland, and nobody throws things off the rocks anymore, thank goodness. So what's out there is what's out there. We'll come back to that under the rules.

The color tells you what the glass was, and how much of it there was to begin with, which is why some are common and some you'll wait years for. This is our chart, worked out from fifteen years of jars and from comparing notes with other people who do this. Other beaches vary; a beach below an old bottling plant will be different from ours.

We grade every piece before it goes in the jar, with a simple A-B-C, and it keeps the jar honest.

• A — Fully frosted on every surface, no shine anywhere, every edge and corner rounded, thick, with the fine pitting all over. It looks like a candy and feels like a stone. These are the ones that go in the window jar, and if we ever made jewelry, which we don't, these are the only ones that could.
• B — Frosted and rounded, but with one flat face still a little glossy, or one corner that isn't quite soft, or thin enough that you can see it won't last. Most of what we find. Goes in the year's jar, counts in the count.
• C — Still shiny, still has an edge you could cut a finger on, or clearly a recent bottle. Not done. Goes back in the water. We mean it. The sea isn't finished, and in twenty years somebody's grandchild will find it and it'll be an A.

How to check: hold it up to the light and turn it. Any surface that flashes is unfrosted. Run your thumb over every edge with your eyes closed. If you feel a line, it's a C. Mike also taps it on his front tooth, which tells him something, he says. I don't do that.

Low tide. The tide here runs nine to twelve feet, which means at low water there's a great deal of beach that's under the sea most of the day, and that's where the glass is. We go out on the falling tide and walk the wrack line and the gravel bars as they come up. The biggest tides, around the new moon and the full moon, uncover the most.

After a storm. This is the real secret. A good nor'easter, or any few days of onshore wind and heavy surf, digs up the bottom and throws everything up on the beach in a new arrangement. The morning after, and for two or three mornings after that, is when the cobalt and the lavender turn up. It's cold, it's wet, and we've had some of our best hours of the year with the rain coming sideways. In the winter after a big blow we've gone out at first light in January with the thermometer at eleven degrees. Get the kind of gloves you can pick up a pebble in.

Gravel beaches, not sand. Fine sand beaches are lovely and mostly empty. Sea glass collects where the pebbles collect: the coves with a cobble beach, the gravel bars, the tide pools. Look at the pebble line, the band of small stones the last high tide left, and walk it slowly. Look for the color that doesn't belong. Then look again, because the good ones are nearly the color of wet stone.

Old places. As we said: near the old town landing, the old cannery, the ferry slip, the point where the summer cottages have been since 1900. Not the wild beaches.

Slowly. A mile in an hour is about right. Mike walks the upper line and I walk the lower and we cross at the end. If you're walking fast you're getting exercise, which is fine, but you're not finding glass.

1. Stay off private beaches. Here's something people from away don't know: in Maine, unlike most states, the beach between the high and low tide lines generally belongs to the owner of the land above it, and the public's right to be there is only for fishing, fowling and navigation. Picking up glass isn't any of those. So we hunt the public beaches, the town landings, the state and town parks, and the places where we've asked and been told yes. If there's a cottage looking down at you and you haven't asked, you're on somebody's front lawn.
2. Ask about parks. Some parks and preserves don't want anything carried off, glass included. A sign or a ranger will tell you. If it says no, it's no.
3. Throw back the C's. Said above. Saying it again.
4. Don't dig. Don't turn over the beach with a trowel or a rake, don't dig at the bank, don't disturb the dune grass. What's on top is what the sea offered today. Tomorrow it'll offer something else.
5. Don't take it all. Some days, after a storm, there's more than we could carry. We take what we'll look at and love and leave the rest for the next person, and for the kids, especially. A child who finds a piece of blue glass on a beach is a child who'll come back to the sea for the rest of her life. Leave a few for her.
6. Don't sell it. That's our rule for ourselves, not for anybody else, but here it is. Once it's for sale you're not looking at the beach anymore, you're looking at inventory.
7. Pick up the real trash. One bag for glass, one bag for the rest. We've never come home with the second bag empty.

Every January 1 we start a new quart canning jar on the kitchen windowsill and everything we find that year goes in it, with a count kept in a notebook by color. On New Year's Eve we pour it out on the table and sort it and argue and then it goes into the big jars in the front room. Here is where 1999 stands as of September 20, after a slow summer and one good blow in early September.

The window jar. This is the main thing and it's barely a thing. A big old glass jar, the kind pickles came in at the store, on the sill of the south window in the front room, filled with A's only, all colors mixed. When the afternoon sun comes through it the whole wall goes green and blue and the cat sits in it. That's what fifteen years of walking comes to and it's enough.

The color jars. Smaller jars along the same sill, one per color, for the ones that aren't white or green or brown. The cobalt jar has, after fifteen years, about two inches in it. Guests always pick it up.

A stepping stone. Mike set a few dozen B's into the top of a concrete stepping stone he poured in a pie tin, for the garden path. It's held up through three winters. The colors went a little dull in the concrete, so use the ones you don't mind.

A wind chime, which was my idea, with pieces wrapped in copper wire and hung from a piece of driftwood. It sounds nice. It doesn't sound like much. It's fine.

What we don't do: drill it, glue it to picture frames, make jewelry of it, or sell it. Other people do those things beautifully and we've seen lovely work. We just found that once a piece is a craft supply it stops being a piece of the beach, and the beach was the point. The jar is where we look at it, and mostly we look at it and think about the morning we found it, which is the real collection.

There's a lady on Sanibel Island down in Florida who walks her beach every morning for shells the way we walk ours for glass, and her Beachcomber's Log is the page on GeoCities that feels most like ours. Different beach, same reason.