I have a folder on my desktop of images I love, and that have stuck with me over the years. When I’m feeling blue, or uninspired, or lazy, I take a peek at some of them for an instant visual pick-me-up. This is one of my favourites - a conceptual poster by a designer named Roland Tiangco. The back of the poster is coated with pigment, and the front is spot-varnished (more on the production here). As you unfold the poster, your hands inevitably get stained with the pigment on the back, which ends up getting onto the front, revealing the hidden message. So simple, but so powerful.
Original source: http://www.wallpaper.com/directory/1964