I have two guitars that were signed by artists over 20 years ago. I rarely remove them from the case.
One is a white flying V knock off with signatures all over the body.
One is an ESP LTD MV-300, with a dark blue-ish finish.
Both were signed with black sharpie.
How can I protect both?
I would comment but don't have 50 reps!
Do you know what kind of finish is on the guitars, depending on the type of finish you can just add another coat of that finish or a lacquer that doesn't react with the guitar finish. Some finishes have a colour tint to them but you should use a clear coat to avoid creating a darker tint to the applied area.
Always test out on a scrap piece of wood before applying to your guitars. If in any doubt take it to a Luthier who can advise the best type of lacquer to apply and may do it for you.
Here is some info on various finishes found on guitars https://acousticmusic.org/research/guitar-information/guitar-finishes/
I would expect the flying v would be a poly type finish, but not sure about the ESP.
