Most street artists add to the urban environment to make a statement. But Stefaan de Croock takes away instead: he uses a pressure washer to carve graffiti into the natural dirt and growth that cover our cityscapes, and the results are quite amazing.
Moss has a tendency to grow rapidly on concrete walls, especially when they're regularly damp. That's something de Croock—AKA Strook—takes advantage of. This series of images shows off his signature "subtractive graffiti", cut into a wall of moss outside the STUK art center in Leuven, Belgium.
I've never seen an artwork describe the materials used simply as "water" before now. Sadly, the moss grows back quickly so within a few weeks of creating such pieces they're diffiuclt to see. Not to worry: they're preserved in some detail over on de Croock's website. [Stefaan de Croock via Web Urbanist]