I have a guitar with a particularly light-colored rosewood fretboard. I love the way it looks when I apply lemon oil, but that only lasts a day or so. I have some wipe-on poly I’ve been itching to rub in to see if I can get a beautiful depth to that board. Would this damage the guitar? Alternatively, is there an oil that would shine it up and last a good deal longer? —Will Sutter
In general, I advise against using anything beyond the usual fretboard oils. Wipe-on poly and other such products are designed to build a film on a surface. This is not what you want on a fretboard—generally, an unfinished surface is what most of us are used to feeling. A poly treatment could also complicate future service such as refrets or even fret dressing. Also, since your fretboard surely already has oils, sweat, and other goodies deeply impregnated into the surface, I would not bet too much on proper adhesion between the poly and the surface. The product might never dry correctly, or it might dry and then peel off—neither of which is a desirable outcome.
Most lemon oils on the market are, in fact, mineral oils with some lemon scent added, or a small percentage of actual lemon oil. These do a great job of wetting the surface and making everything look nice, but the mineral oil never dries completely, so the effect tends to not last very long.
There are some oil products on the market that are designed to polymerize upon exposure to oxygen. Some of these, such as tung oil, have been used historically as wood finishes. However, many of these drying oil products have metallic drying agents such as cobalt mixed in that are somewhat toxic, and that can tend to make the dried oil gel closer to the surface rather than penetrating.
Some natural oils, like walnut oil, can oxidize to a dry state and last longer than the usual lemon oils. I have used the Preserve nut-oil–based salad bowl finish successfully; that is food safe and will dry.
I have also had some recent success using paste wax as a fretboard treatment, rather than oil. Applied with some energetic friction, it leaves a lovely, dark, and glossy surface that persists longer than the oils. The Renaissance brand of microcrystalline wax is a popular choice and a good recommendation. Be careful to avoid hardware-store waxes (Briwax, for example), which contain solvents such as toluene. These are unhealthy for you and your guitar!
As always, I recommend moderation with oils and waxes. I have seen loose frets caused by overzealous oiling, and please don’t treat any lacquered or finished surfaces with oil—it will not help them and can actually cause problems. Give the wax a try, and good luck!
