The word “graffiti” usually conjures images of people with spray cans illegally making murals or jotting down tags using colorful paints. A lot artistic interventions use other tools and materials, though, subverting expectations and working in (literal and legal) gray areas to create works without leaving a conventional trace. Consider, for instance, the massive deep sea monsters, jungle predators and swamp creatures of Russian illustrator Nikita Golubev that lurk in the grimy shadows on the sides and backs of trucks.

Along similar lines, this series of skulls by artist Orion was made by scrubbing car exhaust from an active tunnel. For those looking to deter street art and artists, subtractive interventions like these can be tricky to pin down. After all, Golubev and Orion are simply cleaning vehicles or public surfaces, albeit very selectively. In many cases, the end result is actually further cleaning — art like this often pushes municipalities to send out teams that then wash off entire areas to make them look consistent again.

This artistic approach draws different reactions depending on the scale and situation. Take snow calligraphy, for instance — few people seem to mind a nice message traced into the hood of their car. Artist Faust notes that virtually “everyone has an affinity for writing in the snow as a child,” so perhaps it’s also something people feel they can relate to on a more experiential level.

Reverse graffiti not only provokes different response—it also spans a variety of materials and methods and can work with greenery as well as it does with snow or grime. Some moss artists work additively, creating mixtures to apply to surfaces and thus encouraging moss to follow particular grown patterns to produce an specific result. Others, however, actively remove moss to create desired words, patterns and illustrations.

Stefaan de Croock falls into the latter category, using power-washing tools to create cityscapes and other whimsical scenes on surfaces previously covered in layers of moss. As with a lot of reverse graffiti projects, his pieces are generally temporary — the moss simply grows back in to fill the voids over time.

SpY’s work in Besancon, France, combines elements of reverse graffiti and tree sculpting. Turning topiary approaches into a mural-making technique, he shaped vines into a circular work of wall art using an elevated work platform, trimming his way toward a perfect circle.

Light art and projection bombing are even more temporary and generally even less invasive than reverse graffiti. Lighting machines aimed at buildings to create patterns or spell out messages can be targeted and disabled if they persist, but ephemeral light painting like the above work by Lichtfaktor are deployed quickly using glowsticks or other portable devices and have to be captured on camera to work, making them brilliantly elusive.

Meanwhile, if light art is about brief visibility, then hydrophobic spray art is about lasting invisibility. Both are made to be seen and not seen in particular ways, but the latter has a key ingredient that determines when a design or artwork is visible: wetness.

When the hydrophobic NeverWet spray came out, it promised to waterproof everything, but some users found they had mixed results in applying it to things like clothing and touchscreens – it discolored shoes and left a sticky film on devices. Then someone thought to create a stencil and tag sidewalks with the stuff and a new type of visible-when-wet graffiti was born. One can, of course, free-spray with it as well, but stencils help make the outcome more controlled and predictable.

The same basic artistic idea has been applied in other contexts by designers, too — selective hydrophobia can be incorporated into brick pavers or concrete sidewalks, for instance, to create patterns that change with the weather. Clever urbanists might consider ways to integrate useful messages or wayfinding elements into such projects, like arrows pointing to nearest sources of shelter in a storm. Similarly, messages that appear on surfaces that change color with temperature could be used to guide people on particularly hot or cold days.

Practical designs aside, artists continue to experiment outside of traditional material palettes with works that raise questions about visibility and invisibility. There is fun to be found at the intersections of these ideas, embodied in projects like this one by 3D artist Milane Ramsi, who combined different approaches into a single installation — a concrete pillar appears to vanish while simultaneously revealing three-dimensional lettering more reminiscent of conventional graffiti.

Additive or subtractive, vandalism has its grey areas, but what about the seemingly more straightforward removal of graffiti? Here again there are shades of gray. Some artists, like Mathieu Tremblin, paint a surface clean then write over graffiti with their own work — in his case: humorously replacing loose tags with digital-style tag clouds. That, clearly, is of a kind with what was underneath; in places where tagging is illegal, replacement tags are too.

Then there is the saga of the infamous Banksy and the so-called Gray Ghost, an anti-street artist who leaves signature splotches of gray in the wake of his graffiti removals. Some argue the Ghost’s work vandalizes art — others say it is itself art. Legally, like Banksy’s illegal murals, both artists work in a similar space, though in Banksy’s case building owners often go to great lengths to preserve his art, in part for its monetary value.

Exceptions aside, municipal laws are usually clear on painted public art and the goal is generally total graffiti erasure, though it doesn’t always work out that way. This kind of official cleanup usually draws binary responses, viewed by some as a welcome fix and by others as an act of defacement. One award-winning film, however, argues for a third point of view: graffiti removal as the ultimate next step in the progression of modern art. Despite its semi-satirical intent, The Subconscious Art of Graffiti Removal raises provocative questions about what constitutes street artwork in the gray areas of additive and subtractive graffiti.

In Brooklyn, the latest iteration of BEYOND THE STREETS lets visitors check out the work of more than 150 street artists from around the world. Curated by graffiti historian and “urban anthropologist” Roger Gastman, who’s also known for co-authoring books on street art and co-producing films like Banksy’s Exit Through the Gift Shop, the show first opened in Los Angeles last year. Now, it’s up at the new 25 Kent Avenue space on the edge of Williamsburg and Greenpoint with a whole new collection of art spread out over two floors.

Among the biggest names you’ll find at the show include conceptual artist Jenny Holzer, feminist art collective Guerrilla Girls, Shepard Fairey and Takashi Murakami. Sculptures, works on canvas and immersive installations share space with a Beastie Boys installation featuring “artifacts and ephemera” from the band’s 4-decade history, a functioning tattoo parlor by Bert Krak & Alexis Ross and a room of puppets made of trash by Paul INSECT and BAST.

For Gastman, what distinguishes the show isn’t just its diverse array of work, but the fact that it celebrates artists who spent years illegally working on the street. While the developers who are drastically changing cities and making them more homogenous might actually like to see officially sanctioned murals around as a way to “clean up the neighborhood,” graffiti artists who broke the rules (and sometimes paid the price) shaped street art as we know it, says Gastman. Many of the artists in the show started working under the cover of darkness, but now have their own prolific studio practices.

“You know, this culture—which was started by youths writing their names over and over again for the sake of fame and fun and notoriety—has ballooned into a worldwide cultural phenomenon,” says Gastman in an interview with Artnet. “So many of the pioneers are still with us today. A lot of them are getting older. But let’s learn from them. Let’s respect them. And let’s preserve the history as much as we can while they’re with us, before it’s too late.”

BEYOND THE STREETS NYC opened on June 21st and will run through the end of August 2019. If you can’t make it in person, peruse the artists and their work on the BEYOND THE STREETS website and check out some of the standout pieces at Gothamist and High Snobiety.

Why, Banksy wonders, has he never been invited to the Venice Biennale? Perhaps because they knew he’d do something just like this, invited or not. The elusive British street artist set up an unauthorized stall in what appears to be the city’s famous Piazza San Marco, displaying a nine-panel oil painting of a cruise ship. The piece references the chronic problem of overcrowding in Venice due to tourist activity, leading many residents to call for a ban on cruise ships.

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Posting a video of the kiosk on Instagram (which is essentially the artist’s way of verifying that a work is his), Banksy reveals that he was ultimately told to leave due to lack of a permit.

The artist also claimed responsibility for a new mural that popped up on the wall of a private home along the canal, showing a migrant child holding a pink flare. That piece is likely a response to Italy’s recent actions against migrants, which have led to the closure of ports. Italian forces are said to have ignored ships full of refugees, allowing them to capsize with hundreds of people on board. At least 250 drowned.

Over the past half-century, street art has evolved from squiggled lettering on subway cars to a cultural force practiced in virtually every corner of the globe. It began unsanctioned and disdained, and though some prominent street artists now sell their work for millions behind gallery doors, it remains firmly rooted in counterculture, simultaneously celebrated and dismissed. What separates it from merely decorative murals is its message, even if it doesn’t appear to be saying anything at all: its very existence empowers people with little to no voice in society.

Messages By the People, For the People

As a movement, modern street art is primarily rooted in the 20th century, but of course, art and text scrawled on public surfaces has existed far longer than that. From cave paintings and engraved Arabic rock graffiti to inscriptions written by ancient tourists in the tomb of Ramesses VI, humans have always sought to leave their mark on the world in this form. Even the ancient Romans used graffiti to declare their love, insult each other and ridicule their leaders, with many examples unearthed in the ruins of Pompeii.

This kind of free, uncensored expression using the city walls as a canvas has always been classified as vandalism by those seeking to uphold both order and distinctions of class. Pristine paint jobs convey a message of their own: “We have things under control here. We’re civilized.” Beneath that often lies a concerted effort to suppress the urban poor and their frustrations, especially in times of transition when their cities begin to rapidly change, leaving them behind. To scrawl a message on a wall is to speak back to authority in a public forum and foment a sense of solidarity with those in similar positions.

Street art has flourished in various forms throughout the world, often as an expression of identity with a defiant political slant. Movimiento Muralista Mexicano, the Mexican street art movement founded in the 1920s by Diego Rivera, Clemente Orozco and David Siqueiros popularized political murals in a wave that soon spread throughout Latin America and the United States. One notable early example is the anti-imperialist “America Tropical” mural on Olvera Street in Los Angeles, depicting a crucified Chicano besieged by an eagle representing America. The piece, completed in 1932 by Siqueiros, was subsequently covered up and then restored.

During World War II, Nazis used graffiti to spread propaganda, but more often, it was a tool of resistance. A nonviolent German antifascist group called The White Rose conducted an anonymous leaflet and graffiti campaign calling for active opposition to Hitler’s regime, using tin stencils to write slogans like “Down with Hitler” and “Freedom” on the walls of buildings throughout Munich before their arrest by the Gestapo in 1943. One of the group’s leaders was Sophie Scholl, who lamented just before her execution at age 21, “Such a fine, sunny day, and I have to go. But what does my death matter, if through us thousands of people are awakened and stirred to action?”

Pushing the Boundaries and Changing Perceptions

By the 1970s in New York City, street art was often seen as a symptom of economic sickness, taking over train cars, brick facades, concrete walls and other surfaces in a period of great unrest. The city was bankrupt, crime rates skyrocketed, unemployment topped ten percent and there was at least one abandoned building on every block. As over a million residents fled, those who were left behind weathered the storm together.

All five boroughs and beyond became one big art studio, whether you were a poet in Chelsea or a poor youth from Queens channeling your frustrations and boredom through a can of paint. Artists like Taki 183, Tracy 168, Dondi, Lady Pink, Zephyr, Revolt and Seen tagged every imaginable surface in a free-for-all that encouraged experimentation and competition. In the meantime, as the burgeoning crack epidemic, street gangs and other symptoms of poverty and oppression became associated with graffiti, penalties grew more severe. The city’s “war on graffiti” waged on – but it wasn’t long before street art began to enter the mainstream, changing the game.

Artists with roots in street art who gained credibility in the art world gave outsiders a new perspective on the movement, bringing marginalized identities to an institution that’s overwhelmingly white, straight and wealthy. Jean-Michel Basquiat, an American artist of Haitian and Puerto Rican descent, and Keith Haring, a gay man who spent much of his career working to raise awareness about AIDS before dying of AIDS-related complications himself in 1990, are two notable examples.

The distinctions between graffiti and art began to blur, and the scope of expression began to widen as new forms of media were introduced. Commissions to produce sanctioned murals in public spaces multiplied, though many artists choose to remain on the dark side of the law on principle. Artists like Shepard Fairey spun early experiments with street art into business empires, and some cities began to legalize graffiti art and even encourage it.

Street Art as a Catalyst for Change

The internet helped sweep the world of street art from its anarchic subcultural origins to a big money industry, for better or worse. It’s more accessible and widely viewed than ever, with the audience for any given piece going from the hundreds that may have passed it on the street to, potentially, millions. The fight over its commercialization is ongoing – just look at any recent Banksy-related stories for confirmation – but its anti-establishment spirit lives on.

Today, street art campaigns by artists like Banksy, JR, BLU, ROA and many more make statements about climate change, environmental degradation, human trafficking, capitalism, fascism and hope in times of darkness. There’s still a perpetual battle between those who would speak to the world through street art and those who would silence them – exemplified by Egypt’s 2011 revolution, the artists who plastered streets like Mohamad Mahmoud with political works and the military dictatorship that has since clamped back down on the region.

In Gaza, Banksy is just the most well-known of many artists to create visual public commentaries on the injustice that takes place there every day. In Brazil, artists like MurOne and Haas&Hahn work to invigorate the poorest favelas with graphic murals and bring international attention to dilapidated and under-served neighborhoods.

Just take a walk through your own neighborhood to find signs of street art’s immediacy and vitality and its ability to instantly respond to world events through a diverse variety of perspectives. As much as it (and the world) has changed over the past century, street art remains one of the most democratic and resilient means of expression, and its value can’t be overstated.

Street artist Ron English paid over $730K for a work of art by Banksy – and he plans to paint over it. It might sound like some kind of silly high-profile artist feud, but English harbors no animosity toward the infamously anonymous creator of ‘Slave Labour,’ the mural he just bought at auction. He just doesn’t want anyone else to have it.

The mural, which depicts a small child on his knees with a sewing machine producing a string of Union Jack bunting, was originally painted onto the side of a London store in protest of sweatshop souvenirs before the 2012 Olympics. The mural disappeared in 2013, to the anger of local residents, and later resurfaced to be sold at auction for $1.1 million. It’s all part of an ongoing scheme in which building owners have Banksy works chiseled off their property and sold at auction without the artist’s consent.

Ron English, an American contemporary artist known for vivid, often satirical works with a comic book aesthetic, is sick of it.

“My idea for this painting is to whitewash it for my good pal Banksy, I only wish I could’ve spent more money for it,” English told a crowd of reporters in Los Angeles. “I’m going to paint it white again, I’m done. This is a blow for street art. It shouldn’t be bought and sold. I’m going to paint over it and just include it in one of the walls in my house. We’re tired of people stealing our stuff off the streets and re-selling it so I’m just going to buy everything I can get my hands on and whitewash it.”

But, English notes, while he might be crazy, he’s not stupid. He plans to sell the whitewashed painting for a million dollars – and he’ll probably get it.

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In October, Banksy’s work Girl with Balloon literally self-destructed the moment it was sold at auction for more than £1 million at Sotheby’s in front of an astonished crowd.

Learn more at WebUrbanist’s Banksy archive.