Q: The rosewood fingerboard of my guitar has gradually gotten very dry-looking with faint white residue appearing in spots. What’s causing this and is there a way to correct it without having to send it in?
A: There are several reasons fingerboards dry out. Those players living in very hot and dry areas (like Phoenix or Las Vegas) are much more likely to experience problems with dryness because the humidity there (and in any other desert areas) is very low. Also, guitarists that live in the northern states where the heat is on much of the year will tend to see more dryness, since heaters rob the air of moisture.
First off, you definitely need to apply a coating of fingerboard oil to keep the fingerboard wood suitably moist. Gibson offers what it calls Fretboard Conditioner for under $3 for a 4-ounce bottle (honestly, every guitar owner should have this on hand), while Dunlop makes a full care kit for under $30 that includes everything you need to keep your guitar in perfect condition, including two 100% cotton cloths. There are all sorts of products and kits in between; your Sales Engineer can help you choose one.
As for the white residue, it’s possible that some sort of preservative was applied to the fingerboard and when the residual moisture evaporated, it turned into a powdery substance. It’s also possible that it’s grime that’s built up – be sure to wash your hands before playing. If it continues and you’ve determined it’s not from your hands, play it safe and have a qualified guitar tech check your guitar out.