Play-Doh is a commercial plastic modeling compound similar in texture to bread dough that has been sold as a children's toy around the world for a half century. Its exact makeup is a secret, but is primarily a mixture of wheat flour, water, deodorized kerosene or another petroleum distillate (which provides the smooth texture), salt, a drying agent such as borax (which deters mold), an alum-based hardening agent, and colorings and perfume.
It is non-toxic, non-staining, and is soluble in soapy water. When kept in a sealed container, Play-Doh remains pliable, but when exposed to air it hardens in about a day, making it good for children's craft projects.
Play-Doh was invented by Noah McVicker and Joseph McVicker in 1956 and awarded U.S. Patent 3,167,440 in 1965. One of many common products invented by accident; it was meant as a wallpaper cleaner. It was marketed by toy manufacturer Rainbow Crafts and first sold at the Woodward & Lothrop department store in Washington, DC.