If you have ever tried writing on a plastic surface with a Sharpie or other permanent marker, you have probably discovered that the ink can easily smear, rub off and disappear over time. But, with proper preparation, you can get your Sharpie to stick to just about any plastic surface imaginable.
Clean the Surface
Clean the plastic surface to remove oils and dirt. Do so carefully so as not to damage the surface. Dampen a soft cloth with warm water, and, using a mild dish soap, gently rub the surface you will be working on. Pat with a dry cloth. Then, use isopropyl alcohol and a cotton ball and wipe the surface again to ensure your surface is completely clean. Allow the surface to dry.
Prepare the Surface
Sand the surface you are writing on using a fine-grained 120-grit sandpaper. This gives the smooth plastic surface some "tooth," or a slightly rough, porous surface, which allows the marker ink to adhere to the plastic. Make sure to only sand where you plan to write, as you may not want the sanded surface to be too noticeable. Wipe clean with a damp cloth and let dry.
The newly prepared plastic surface is now ready for writing. Now that you've removed the smooth surface, the marker ink will sink into the microscopic holes in the newly porous surface. Keep in mind, therefore, that anything you write in this section will be permanent. If you need more writing room, clean and sand more of the surface. Try to plan your writing so you do not have too much or too little prepared surface. Allow the writing to dry thoroughly, preferably overnight.
Even though your writing is permanent, it still may fade over time. Also, the roughened writing surface will attract dirt and oils from fingerprints more easily than the non-sanded surface. To prevent this, coat your writing with a layer of clear nail polish or a coat of matte polyurethane. Once it's completely dry, the clear-coat will shine, helping to hide the sanded surface not covered by writing. Choose the polyurethane for a matte, dull finish.