It was a rough winter here in the northeast. I must have thrown close to 200 pounds of rock salt at my sidewalk and driveway between Christmas and Easter this year to melt the seemingly constant ice and slush accumulations. It's a simple act, really: just fling some rock salt at the ice, and poof! a few hours later, the ice is melted away.
But what is really happening during this melting process at the crystalline level is very interesting from a purely aesthetic level, as the rock salt crystals interact with the ice crystals to create saline water.
I tinted the rock salt blue and green by mixing food coloring in with water and allowing the rock salt to partially dissolve and then recrystalize as the water evaporated out. I tinted the ice red by adding food dye in layers of near-freezing water and repeating until the color was distributed through the thickness of the ice slabs.
Images were captured with Sigma 70mm f2.8 EX DG and Sigma 50mm f2.8 EX DG macro lenses on a Canon EOS 5D, Rebel XTi and 20D at one or two second intervals. Animation rendered in Photoshop CS5 Extended and Adobe After Effects.
I'm going to experiment more with this process. It is very interesting having two crystalline structures dissolve into each other.