For many years, guerrilla marketing has been seen as the sole providence of dodgy businessmen, obscure record stores and independent nightclubs. But the times they are a-changing. Now accepted as an important element in the brand-building toolkit, it has been rapidly adopted by mainstream brands such as Diesel, Microsoft, BMW and Royal & Sun Alliance.

Guerrilla marketing techniques, defined as an unconventional way of performing promotional activities on a very low budget. have been around for years, but they've also acquired a bad rep for sometimes defacing public property. The term also includes any kind of promotional activity which is remotely subversive, unorthodox or even technically illegal. Examples range from a fake funeral procession to staged murder scenes, complete with police tape. However, the vast bulk of guerrilla marketing activity comprises a combination of fly posting, stickering and marketing-related graffiti.

Now Street Advertising Services is offering a less antagonizing—and more legal—solution by creating images out of water. The British company uses high-pressure cleaning machines to wash brands, logos and adverts onto dirty pavements. First, clients provide their design, and SAS turns it into a giant stencil. Then, working at night, their team blasts the stencil with water and steam on dirty walls, roads, pavements or even road signs. The result is a sparkling clean image in the shape of the company's logo or message. Nothing but water and steam are used, and it's all perfectly environmentally friendly and legal.

Brand-building is a tricky business, and with many audiences feeling increasingly alienated by traditional forms of mass communication, the temptation to turn to more ecological means of connecting with them is strong. People are swamped with billboards and this was a more subtle and cheaper way of introducing the brand. Firms which once feared getting into trouble, now find guerrilla tactics more acceptable.

SAS has operated primarily in the UK so far, but it's open to projects anywhere in the world (as long as there's dirty pavement!). The company is also open to explore reciprocal arrangements with other entrepreneurial enterprises. So much dirty pavement, so little time....