Fretboards can be some of the dirtiest parts on guitars. Fretboards collect all the dirt and grime that comes from your fingers, as you play the guitars. The fretboard also collects dust from the strings and frets as they wear together. All of this combines to make a really gross black film of dirt on the fretboard. If you have been a repairman for long, I'm sure you have seen some pretty gross guitars come across your guitar repair bench. I remember this one guy brought in his 1970's Gibson Gospel for a tune up. He claimed that he never cleaned the fretboard. I believe him; it was that bad! Luckily for him, fretboards are easily cleaned with the right tools.
You will need two different sets of guitar fretboard cleaning tools: one for unfinished fretboards and one for finished fretboards.
Guitars with unfinished fretboards can be cleaned with two simple products. I like to use steel wool #0000 and Murphy's Oil soap. The steel wood not only is used to apply the oil soap, it also helps scrape some of the gunk off the fretboard while polishing the frets and fretboard. The oil soap acts as a lubricant to help loosen the dirt. The oil soap also helps condition the fretboard. Simply open the bottle of Murphy's Oil Soap and put some on a piece of steel wool. Tab the steel wool on each piece of fretboard and work the oil soap in. Once you have removed all the dirt, take a piece of paper towel and wipe away the excess oil soap. Let the rest of the oil soap soak into the fretboard for a few minutes and you have a fully cleaned, polished, and conditioned fretboard.
Guitars with finished fretboards are a little different. Do not use either steel wool or oil soap on a finished fretboard. Both of these products will ruin the fretboard finish. Instead, simply use a damp rag or a rag with guitar polish on it to remove the dirt from the fretboard. Remember, finished fretboards will not get as dirty as unfinished fretboards because the finish creates a smooth surface for the dirt to be wiped off during regular play.
I strongly advise getting all three of these products: steel wool, Murphy's Oil Soap, and guitar polish. No set up or repair is complete without properly cleaning the guitar. Whether you are repairing your own guitars or repairing customers' guitars, you will be amazed at how good a properly cleaned fretboard feels on your fingers! If you would like more information about guitar cleaning and maintenance, please see my guitar cleaning and maintenance article.