I use a pure mineral oil (petroleum distillate) on roasewood and ebony fretboards. The traditional "lemon oil" used on the unsealed rosewood/ebony fingerboards of guitars and other stringed instruments is NOT made from lemons. Contrary to popular assumption, the lemon oil commonly used for treatment of wood has no association with the lemon at all. It's a different product all together and got its name from its color and tart/lemony smell, and should not be confused with the corrosive oil of lemons that should not be used on fretboards.
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