For street artists, the whole world is a gallery

CAMBRIDGE -- On a sunny, slightly chilly Sunday morning, Adam Geremia is on his hands and knees in the Pit in Harvard Square, painstakingly arranging saltines to spell out a kind of haiku on the bricks. When he's finished, the three-line cracker poem, which he planned out the night before on graph paper, reads: "After brushing -- /two handfuls/

of cold water." Why, a bystander asks, are you doing this? Geremia, 27, doesn't offer a complex explanation: "If I did it at home it wouldn't be as much fun," he says. And why crackers? Haiku try to capture ephemeral moments, Geremia says, and it seems fitting to use a medium just as impermanent.

Less than two minutes after the poem is complete, a man walks right through it, scattering the crackers in all directions. Geremia, looking distressed, as if he isn't quite ready for the impermanence to set in, gathers up the crackers and puts them back in place. Not 30 seconds later, a group of people walk into it again, and the crackers go flying. The ephemeral cycle is complete.

Geremia is part of a small but dedicated subculture of artists who use public spaces as their galleries. They bolt wooden monsters to walls of abandoned buildings, tie videotapes bearing messages to signposts, affix figures drawn on scrap wood to phone booths and bus stop shelters. They don't do it for money or recognition. Their efforts are unpaid and often anonymous; some are illegal.

They do it for the thrill of riding their bikes around at 3 in the morning to put up a piece of artwork that will be seen by hundreds, even thousands, of people. They do it to see how people will react to or alter what they have created. And they do it because they have something to say.

On Super Bowl Sunday in New York, two friends wrapped painted plywood, two-by-fours, drills, chains, bolts, screws, epoxy, and cameras -- 50 pounds in all -- in trash bags, bound them with twine, and strapped them to their shoulders. They took the subway from Brooklyn to Manhattan, hopped in a cab, then walked 22 blocks in ankle-deep snow along an abandoned elevated railway line in the Meatpacking District. As the Super Bowl kicked off, they unpacked their gear and began assembling a 16-foot-long, 7-foot-high wooden monster mouth, attaching it to the railway with chains and bolts. They got home just in time to see the Patriots finish off the Panthers.

The mammoth mouth is part of the Monster Project, which features parts of "a creature that eats the city," according to one founding member, that have been tucked into more than 100 forgotten nooks in New York, Rome, Providence, and Boston over the past four years. The five core members of the group, who are all in their early 20s and prefer to remain anonymous, focus their work on abandoned structures and run-down buildings.

"The idea is to get people to look around more and hopefully to appreciate what we find interesting in the city, with or without a monster there," says a founding member. Locally, weathered claws and mouths peek out above a nail salon in Davis Square, above a diner near MIT, on doorways and unused stairwells and rusty fences.

"It's pointing out this urban beauty," says the Cambridge native, now based in New York, who says some of the projects have been taken down in 15 minutes, and some have lasted for years.

This type of unsanctioned public art exists all over the world, from spray-painted stencils in London to drawings of babies stuck to trash cans in San Francisco to styrofoam cups spelling out "You are beautiful" in a Chicago chain-link fence. It's so prevalent in New York that a walking tour of Lower Manhattan's street art took place in May.

Some street artists have become famous: Keith Haring started out doing chalk drawings in New York subways; Shepard Fairey's Andre the Giant stickers can be seen posted in public places around the country; Barry McGee, who has an installation at the Rose Art Museum at Brandeis through July 25, began doing graffiti art on the streets of San Francisco in the 1980s.

McGee has been a big influence on several local street artists. Raphaela Platow, who curated the Brandeis show, argues that their work is a subtle and sometimes subversive way of making people more aware of what surrounds them.

"They introduce a visual vocabulary into the landscape that we are not familiar with, that triggers different emotions and different thought processes, sometimes even a giggle," she says.

Platow admires the prolific street art of Caleb Neelon, who by his estimation has bolted about 700 of his small acrylic paintings on plywood to signposts around Cambridge, Somerville, and Boston. A yellow thought bubble with "Internal critique" written inside hangs below a "Slow children" sign; a periwinkle elephant looks up toward a sign designating two-hour parking. It's a pursuit he calls the "Signs of Life" project, a "harmless and gentle form of unsanctioned public art."

"It's kind of like a squirrel hiding seeds for the winter," says Neelon, 28, who recently graduated from Harvard's Graduate School of Education.

Neelon, who also goes by Sonik and recently published a children's book, has a background in graffiti art. Being a street artist has taught him not to be precious about what he's doing, he says; once a sign is up, after all, it can taken by a passerby, removed by the city, or broken in a windstorm.

After the bottom square of Neelon's three-part sign in Porter Square disappeared a few months ago, the message changed dramatically, from "The kids will have their say" to "The kids will have." As Neelon puts it: "I like art to have a story."

Affixing artwork to public walls or signposts is considered a crime against property if the property is damaged, according to the Boston Police Department. But if no physical damage is done, the art is classified as abandoned property. Street artists could be subject to arrest, said Lieutenant Paul Trant of the Somerville Police Department, but someone putting up a painting might be treated differently than someone with a spray-paint can in his hands.Even more prolific than Neelon's street signs are the "Santa is real" tags that are stenciled on sidewalks, lampposts, and kiosks throughout Boston. The person behind the message is 42-year-old commercial photographer and conceptual artist Pia Schachter, who, seconds after a narrowly avoided car accident, started to say the words over and over again: "Santa is real. Santa is real." "I was praying to Santa," she says. She decided to share her epiphany during the 2002 Christmas shopping season, beginning in Downtown Crossing. She estimates she spray painted 1,200 of the tags in a three-week period. "I wanted people to look at their list in a different way," she says. "Instead of a list of obligations, I wanted them to look at their list of names as a list of people they can bring happiness to." Like other street artists, she likes seeing people alter her work. One of her favorites simply added one word to make it: "Santa is real fat." She didn't go out during the 2003 Christmas shopping season, but she plans to make the "Santa is real" rounds next winter, hopefully as part of a legal project with a group of kids."I think kids are told too early that Santa isn't real," she says. Her three-word message, she says, is about "trying to prolong magic." People may find another message from a street artist inside newspaper boxes around the city. Massachusetts College of Art printmaking major Rose Fortuna goes out at 5 a.m. to tuck her colorful personal ads, accompanied by silk-screened drawings of herself, inside the Metro and other free papers.

One says "Hi my name is Rose. My interests are 1. hugging bunnies, 2. making messes, 3. drawing chickens, 4. brushing my teeth, and 5. popping bubbles." Fortuna, 23, says her artwork is a response to traditional personal ads. She was intrigued by "the hunt for that perfect person that we all yearn for" and wanted to have what she calls a "visual conversation" with the public.

"I'm really interested in making the city my gallery and making art accessible to everyone," she says. As for the illegal aspect of her work, she says, "I don't feel like it's destructive. . . . I feel like I'm always trying to make things beautiful or fun or evoke some kind of response from people."

But she admits that it gives her a thrill. "It's kind of like this high you get when you're out there doing this and you know you're not supposed to." Thrills and late-night ventures aside, these artists, like most artists, have a point, and they don't want to confine it to a gallery wall. They want the masses to see their work and think about it and even participate in it. Their role, as they see it, is a constructive one. "People who do this," says Neelon, "love the city just as much as someone who works in civic planning." Katie Johnston can be reached at kjohnston@globe.com.