MusicRadar Basics: electric guitar part 10 - how to clean a rosewood fingerboard
Now after a bit of time playing, you might notice that you're getting some muck building up on your fretboard. It's nothing to worry about - it's only your own sweat and dead skin - but you need to clean it. First and foremost to protect the wood, but also because, let's face it, it's disgusting.
The way to do it is using lemon oil, which will clean all the muck right off as well as soak into the wood and protect it.
First, you give the neck a coating. Allow the oil to soak in a bit, and then using an old cloth give it a good scrub. All the rubbish will come off, and your fretboard will look positively radiant. Hooray!
A word of warning though: this only works on rosewood fingerboards. Most fingerboards are rosewood, but there are lots that aren't - some are maple, ebony or other timbers.
If you're not sure what yours is, either check online or at your local guitar shop and they'll tell you. Lemon oil can damage other types of wood, so make sure you do.