The artist Michael Neff uses chalk to trace the shadows cast by the artificially illuminated city, creating drawings that are more ephemeral than the dark patterns themselves.
In an article written for Urban Omnibus (where you can also see a gorgeous slideshow of his work), Neff explains his method:
I draw and photograph all of these works at night. Night in New York City is surprisingly bright. During the day, shadows change quickly, which inevitably results in distorted tracings. Shadows cast by electric lights gave me the opportunity to spend time on each piece and make very intricate drawings. I once spent 3 1/2 hours making a drawing on Hudson Street that was probably 150 feet long and 8 or 10 feet wide.
The photograph is an important part of the process, acting as documentation and a vehicle to share the work, so the fact that the drawing is fugitive doesn’t bother me. But I enjoy hearing that people have run across the drawings in person. There haven’t been that many and they don’t last very long, so there’s something special about encountering the work out in the city itself.