(Hilary Greenbaum and Dana Rubenstein, The New York Times) That a paint salesman from northern Illinois created the tool through which rebels, gang members, artists and anti-Wall Street protesters alike have expressed themselves merely confirms that inventors can neither control nor predict the impact of their innovations. After all, Jack Dorsey never imagined that Twitter would facilitate Anthony Weiner’s self-immolation.

The spray-paint can, however, has eminently practical origins. Ed Seymour, the proprietor of a Sycamore, Ill., paint company, was in search of an easy way to demonstrate his aluminum coating for painting radiators. His wife suggested a makeshift spray gun, like those used for deodorizers. And so, in 1949, Seymour mixed paint and aerosol in a can with a spray head. As it turned out, compressing paint in a can made for a nice finish.