When I walked into work this morning, I noticed something odd: all the sidewalk tiles were outlined with ragged, chalky lines. It sure was a lot of work to go to to get such a minimal, if striking effect.
The explanation was obvious (look at the top right tiles), and was clearer a little later when I came home. Melting snow and ice filled the cracks first, and then there’s a race between slow diffusion of meltwater and evaporation due to the sun, leaving precipitated salts at the leading edge of the front.
It looked cool, anyway.