During the early 20th century, Kutol Products was the world’s biggest manufacturer of wallpaper cleaning products. But once coal heating in homes was replaced with oil, gas, and electricity, dirty wallpaper became less of a problem and Kutol was in trouble. So in 1956, they pivoted. From Smithsonian:
Joseph McVicker was trying to turn around the struggling company when his sister-in-law read an article about how wallpaper cleaner could be used for modeling projects. Sister-in-law Kay Zufall, a nursery school teacher, tested the nontoxic material with children, who loved molding it into all kinds of shapes. She told McVicker of her discovery and even suggested a new name: Play-Doh…
Originally available in white only in 1956, Play-Doh soon expanded to include basic colors red, blue and yellow. It is now sold in a panoply of hues, including Rose Red, Purple Paradise, Garden Green and Blue Lagoon. The Putty line includes metallic and glittery tints. The recipe has gone through minor modifications over time. At one point, the amount of salt was reduced so the product would not dry out so quickly. But, for the most part, the mixture has remained the same.