A 3M chemist spilled a chemical on her shoe — it repelled stains, and Scotchgard was born

In 1953, a lab technician named Joan Mullan was working on a new fluorochemical compound at 3M's research laboratories in St. Paul, Minnesota. The compound was being developed as a potential additive for rubber jet fuel hoses. During the experiment, Mullan accidentally spilled a few drops of the clear, viscous liquid onto her canvas tennis shoes. She tried to wash it off with soap and water. It did not come off. She tried alcohol. It still did not come off. The spill had permanently bonded to the canvas.

Mullan mentioned the incident to Patsy Sherman, a 3M chemist who had been working on the project. Sherman was intrigued. Rather than seeing a failed experiment, she noticed something remarkable: the spots where the chemical had spilled were completely resistant to stains. Where the rest of the shoe was dirty, the treated areas remained clean. Sherman recognized that the chemical's ability to repel water and oil could be far more valuable than the original rubber hose application.

Sherman and her colleague Samuel Smith spent the next three years developing the technology. In 1956, 3M launched Scotchgard as a fabric protector. The product was an instant success. It was later expanded into carpet protectors, outdoor gear treatments, and industrial applications. Sherman and Smith jointly held 13 patents for the fluorochemical polymers that made Scotchgard work.

Scotchgard became one of 3M's most recognizable and profitable consumer brands. It was used on everything from sofas and carpets to hiking boots and military uniforms. Patsy Sherman was inducted into the National Inventors Hall of Fame in 2001. A chemical that was supposed to be a rubber additive, spilled by accident on a pair of tennis shoes, had become a household name.