From Wikipedia...
Though Sharpie ink will become permanent after setting, it can be easily erased for several hours after writing on many glossy surfaces, most readily smooth metal and glass. Since the ink is based on propanol, butanol and diacetone alcohols, rubbing alcohol will remove permanent ink writing. Sharpie ink can generally be erased from CDs, microscope slides and plastic bottles within several hours. Sharpie ink that has dried for more than several hours can be removed with acetone, but due to the power of the solvent, acetone may damage the surface material. On some surfaces, the ink can be removed by coloring over the ink with a dry erase marker and then removing the Sharpie ink and dry erase marker ink with a dry cloth. Hairspray will also remove from smooth surfaces. Alcohol is particularly effective at removing the ink from skin.
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