Graffiti's long struggle to be seen as valid urban expression, not vandalism, is being crowned this month with an exhibition in Brazil by international artists who not only sprayed official works but also spruced up abandoned corners of Sao Paulo.
A raid on a dilapidated factory by many of the 66 artists on the eve of the event's opening was a celebration of the roots of graffiti, which emerged four decades ago from New York's subway system.
It was also a triumphal declaration that, at last, they believe they have reached legitimacy as contemporary artists, a status enhanced by their provocative legacy.
"Maybe that's why it's an art form. Because after 40 years starting in New York and everything, it still gets people upset. And it is still getting people to think, and it's still making people happy. It still makes people talk," said one of the artists, Anders Rebentlovlarsen, a 25-year-old Dane.
He and the others - around half of them Brazilian, half foreigners from the United States, Europe and Japan - are showcasing more official works in a first Biennial of Graffiti Fine Art at Sao Paulo's Brazilian Museum of Sculpture through October 3.
The designs, which range from a car decked with seductive eyes, though to a Manga-looking girl holding court in front of sinister dolls, a Frankenstein-like head pierced with oversized nails, or an abstract bird's nest of strokes and words, reveal the derivations and reinventions of graffiti as it has spread around the world.
The diversity and intricacy of many of the paintings reinforce the exhibition's argument that graffiti is now a school of art to be reckoned with, perhaps even to be valued by aficionados and collectors.
"Not one work here doesn't bring you a special emotion or something that you are like 'Wow, this person is so talented.' That's art, and that's graffiti fine art," Andrea Luis Carvalho, one of the exhibit's organizers, told AFP.
Rebentlovlarsen, who regularly receives commissions for graffiti commercial projects in his native Copenhagen, said graffiti's paradox is that "you're destroying something but you're actually creating something."
"I can say this is an art form because there's a lot of colors for example, or a lot of people doing it, or it's all around the world, making many people happy. But it's also making a lot of people very angry and nervous, and so that's the clinch," he said.
"I think that's why I find it interesting. Because why is it some people can't see the quality in some non-grey wall for example?"
The curators of the show said they saw Sao Paulo as a natural environment for the works because of the city's boast that it is the New York City of South America, with its melting-pot population, ebullient underground art scene and dizzying, vast landscape of skyscrapers and industrial zones.
Sao Paulo, they claim, is "the current worldwide mecca of graffiti" thanks to those factors - and the blind eye police usually show to graffiti artists whose "vandalism" is considered irrelevant alongside the rampant street crime that poses a much more serious threat to the public.
Rafael Calazans Pierre, a 32-year-old Brazilian industrial artist whose sideline passion for painting walls with interwoven waves and swirls was on show at the museum, said he could not begin to count how many graffiti artists were active in Sao Paulo.
"If you count all the forms of urban expression the people have, there are a lot of people in Sao Paulo doing all kinds of things: some legal, some illegal, some commercial, some anarchist. You find everything here," he said.
The organizers of the Sao Paulo exhibit hope to take the Graffiti Fine Art show to other cities around the world.
Unlike other art events, though, the same works seen here will not be packed up and put on display. Instead, in keeping with graffiti's ephemeral nature, the invited artists will paint their works on site, and see them ultimately dismantled or painted over.
But by brandishing their talent on gallery walls instead of the street, they will not face risk of arrest - only maybe losing their street cred as "urban rebels" and being seen instead as more mainstream creators of contemporary art.