Congratulations, you’re famous. There is a boisterous line of people waiting for you to sign your latest work (or their T-shirt) and inevitably a Sharpie is in your hand. Legendary pen manufacturer Sanford invented this iconic permanent marker in the 1960s using a molded plastic barrel to surround a cotton filament injected with ink. But the Sharpie’s ink isn’t water soluble, which is the secret to its vaunted permanence. The pigment is a chemical cocktail of solvent, resin and the colorant Permachrome—which is also used in inkjet printers. The solvent, xylene, is the key to flow, helping the ingredients blend into a smooth, even ink. (It’s also the source of that distinctive “marker smell.”) Finally, urethane acrylic resin, which also finds its way into house paint, helps the ink adhere to whatever you, the celeb, is signing—a photo, a bestseller or a groupie’s body part. As any high school janitor will tell you, this elixir is notoriously difficult to remove from surfaces. Non-acetone nail polish removers, hairspray and baking soda are said to be helpful for this purpose.