Scientists at 3M in Minnesota were trying to make a better formula for synthetic rubber. The rubber shortages of World War II had made such research important even into the 1950s. As sometimes happens, one of the lab assistants spilled an ounce or so of one of the many compounds onto the tennis shoe of scientist Patsy Sherman. Trying to redeem himself, the lab assistant worked hard to remove the substance from the shoe. Nothing worked, not soap, alcohol, or water. In fact the stained area repelled everything he tried. Sherman and another researcher, Sam Smith, began working with the spilled substance. Between them, they refined the chemical and, in 1956, 3M began selling Scotchgard.