Hobbyist here, non professional.
Can anyone chime in on the use of linseed oil on fingerboards? I was watching a few different YouTube videos and a few guys would rub down the cleaned fingerboards with it. Another would rub it on scuffs and surface wounds on the body.
I grabbed an old neck out of my cadaver corner 2 days ago and cleaned it up and then applied a coat on the FB and a few surface scuffs on the neck. Looks good 2 days later, but what's the long term effect on fingerboards and finishes? What about on guitar bodies?
What potential issues would a future repairperson have to deal with coming across this on a future repair?
My first thoughts were cautious, because I haven't seen any references to this procedure on this forum.
So it's time to ask.
This can be a complex topic, so be prepared to sort through a lot of conflicting info.
Fingerboards are often oiled to give them a richer appearance. Generally, a light mineral oil is preferred because it does not polymerize as do the various vegetable oils. "Lemon oil" is traditionally made of a light mineral oil with a bit of lemon scent added. It is NOT made from squeezed up lemons.
Linseed oil is made from flax seed, and it is chosen for finishes because it DOES polymerize and become a surface coating - a quality not usually desired for fingerboards which can get sticky and nasty before long. You know the polymerization as the gunky stuff that forms around the top of a bottle of olive oil.
Manufacturers have been known to use 3-in-one, lubricating oil, and even WD-40 as a fingerboard treatment.
Me, I'll continue using the mineral oil from the supermarket that's sold for use as a laxative. Wipe on, wipe off, and done.
This is kind of like asking for opinions on a favorite brand of underwear. You'll get lots of differing opinions.
FWIW, I used to use the mineral oil like Mr. Ford. I somehow got onto Howard's Feed and Wax. I think it lasts longer and gives a better sheen to the wood. It is dynamite on any mahogany furniture you may have. Plus it can be bought at Lowes for a very reasonable price.
The choices available for finishing fingerboard surfaces are many and as with stuff these days its a crap shoot as to whether what you are getting or doing is the best solution. Here is our reasoning for our choices, the rest is up to you.
Finishes, for bare wood in particular serve distinct purposes: looks, cleaning and protection.
For looks we see mineral oils and dyes and lemon/orange oils and mineral spirits for cleaning.
For Protection we see Tung, raw and boiled linseed (flax) and many similar nut/vegetable oils. These oils can be combined with Citric Terpene (a distillation of citric peel) otherwize know as D Limonene to assist penetration into wood and by themselves used as a bio degradeable/ecologically sound cleaner.
We use Tung oil and Citric Terpene treatments to condition all our new boards. We have previously used a Boiled Linseed/ D Limonene based preparation (for over twenty years of production) and can verify the effectiveness and serviceability of this system. CT or DL is also a great cleaner for removing embedded grunge and grime - A cut down soft/medium toothbrush is still the best tool for getting up close and personal with the fret junction (that I know). Note: Citric Turpene does not react with Poly/modern finishes and we use nitrocellulose on most of our guitars and have never experienced a reaction or problem. Ditto repairs and reconditioning of older nitro finishes. As usual: if in doubt; test it.
Moving on: The philosophy being that longevity and serviceability of the fingerboard is important at an Artisan and Stage performance level and when correctly applied and buffed/polished provides a level of protection to the wood and the fingerboard.fret junction that will assist in achieving a long life span in adverse (climate, sweat, moisture, alcohol, grimy paws etc) conditions. This is the key to our choice - using the appropriate system for the likely circumstances.
A high level acoustic player who can control the environment in which the guitar will be stored and played may have no need for a protective fingerboard finish and if he/she is a rosewood (or similar) board player with an open grain finish then a protective coating which penetrates the surface layer is a debatable prospect (anything you do can change your instruments tonal response). Good ebony responds well to these oils and darkens a tadge along with highlighting the usually concealed grain patterns and I would have no hesitation using Tung or Flax based oils for all round good looks and protection. Always buff and polish as usual.
To reiterate, if the situation requires protection you should use it (and that goes for guitars as well).
For cheap and nasty it doesn't matter what you use, if the guitar is going to be short lived most wood will stand up to the test without treatment in moderate climates and playing conditions.
So, that's a quick and dirty look at our philosophy and use of fingerboard treatment. Note: do all your fretwork before you oil or clean with anything as the fret filings and grindings love the fret/fingerboard junction, particularly if there is any residual cleaner or oil lingering in this place. Same goes for using steel wool to either smooth or apply finish to the board, which is a very popular cabinet making finish, - it gets into everything as you know (toothbrush job after you use it).