Some new toys and new types of toys are created by accidental innovation. For example, after trying to create a replacement for synthetic rubber, Earl Warrick inadvertently invented "nutty putty" during World War II. Later, Peter Hodgson recognized the potential as a childhood plaything and packaged it as Silly Putty. Similarly, Play-Doh was created as a wallpaper cleaner.[16] In 1943 Richard James was experimenting with springs as part of his military research when he saw one come loose and fall to the floor. He was intrigued by the way it flopped around on the floor. He spent two years fine-tuning the design to find the best gauge of steel and coil; the result was the Slinky, which went on to sell in stores throughout the United States.