Make printed T-shirts powered by the sun! Paint your shirt and place objects on (while it is still wet!) The sun heats up the parts of the T-shirt that are uncovered, but not the parts that are blocked by the objects.When water gets hot, it starts to evaporate, turning from a liquid to a gas. The paint starts to dry, and the water starts to evaporate on the uncovered parts, but under the blocks, it stays wet. As the water evaporates from the T-shirt, water and paint from under the blocks moves out into the dry areas, like how the dry edge of a paper towel picks up spilled juice (or some other image). Eventually, all the paint gets drawn out from under the blocks, leaving you with unpainted shapes on a painted background.
This project is best on a hot sunny day with little wind. To get the sharpest prints, use objects that lie flat around their edges.