Ageing the plastic parts of a guitar, such as the tone and volume knobs and the pickguard, is an important part of the relicing process. Relicing is when you take a new guitar and give it a used or vintage look. You may also want to give plastic guitar parts an aged look if you already have an old or vintage guitar and you need to replace any of these parts, because if you install brand-new parts, they would look too clean and out of place.
Scratch the plastic parts in a few places with the screwdriver. Try to make the scratches look accidental. Scuff the edges of the parts with the scissors.
Rub the parts with sandpaper, using a circular motion. Sand until you have got rid of most of the shine.
Apply a thin layer of wood stain to your plastic parts using a paper towel. On the pickguard, concentrate on the areas that would get the most wear when the guitar is played, such as below the strings. Try to avoid the area under where the strings would be, as this would not naturally get much wear or damage.
Wipe off the wood stain so only some remnants are left of the scratches and the scuffed areas.
Fill a plastic container with a cold black coffee and place the plastic parts inside. Leave them there with the lid on for 24 to 48 hours, depending on how dark you want the parts to be. This will yellow the parts to give them an aged look.
Remove the parts and allow them to dry on paper towels before replacing them on your guitar.
Start off conservatively when scratching and scuffing the guitar. You can always add more scratches, but you can't take them away.