One smell most people remember from childhood is the odor of Play-Doh, the brightly-colored, nontoxic modeling clay. Play-Doh was accidentally invented in 1955 by Joseph and Noah McVicker while trying to make a wallpaper cleaner. It was marketed a year later by toy manufacturer Rainbow Crafts. More than 700 million pounds of Play-Doh have sold since then, but the recipe remains a secret.
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