The manufacturer's name on the headstock of many guitars is applied with a waterslide decal. Waterslide decals are a quick and easy way of branding instruments, but over time they can become chipped and worn. If you are working on a guitar restoration project, you may have to remove the old decal to replace it with a new one.
Take off your guitar's strings, machine heads and ferrules if you are removing decals from under a protective finish of some kind, such as nitro lacquer.
Sand the entire face of the headstock with dampened sandpaper until you get down to the layer with the decal. The sandpaper will smoothly remove all traces of the old decal. Finish sanding to ensure a smooth surface on which you can apply a new finish and decal if desired.
If the decal is on the surface of the headstock without any coating, soak a cloth in hot water with a little vinegar, then lay it over the decal and leave it for an hour. Dry off any excess moisture, then remove the decal with painters tape.
Any residual fragments of the decal can usually be removed by rubbing with a warm, damp cloth. A little lemon juice can help.