Now... people go to lengths finding well-dried and solid timber to them guitars, for Tone.
Isn't soaking them in oil going to soften the wood/affect the tone??
Not for tone - for stability. For most parts of the guitar, moisture content has nothing to do with tone.
As wood dries, it shrinks. If you build with wood which is still too "wet," it shrinks, cracks, and just generally makes you life a royal PITA. I aim for somewhere between 7-9% moisture content. But that's not the whole story - wood stores moisture in different ways, both in the cell, and between the cells. The moisture in the cells is more difficult to remove, and when new moisture gets into wood it will take a lot longer to get into the cells. (This, by the way, is why air dried wood is considered preferable to kiln dried wood - because air drying is so much slower, it keeps the moisture content more even, which - among other things - means the shrinkage is more even.) Once the moisture content is down to where you want it (7-9%), as the wood is held there, the two balance out.
Because of this, most woodworkers try to buy the wood they are going to use as far in advance of actual use as possible (we have some Brazilian Rosewood and German Spruce in the shop which we've had since the seventies - and you can bet that stuff is going for a premium!) I try to never use a piece of wood for a guitar until it has been in the shop for at least a year, but longer is better. This is called acclimatization. Dad figures he's got enough mahogany for necks to last him the rest of his life. (I wish I could say the same, as South African mahogany just recently went on the CITIES list.)
None of this has anything significant to do with tone (though, a really wet top on an
acoustic guitar will sound really tubby - but with the fingerboard its not going to make any difference). The issue is stability. You can never be completely sure what a piece of wood is going to do (as the sign in the shop says, "Carefully selected pieces of wood, under rigorously controlled conditions, will do pretty much as they damn well please"), I can say for certain that wet wood with the moisture content out of balance will ALWAYS be less stable than a piece of dry, well acclimatized wood. I can also say for certain that some kind of finish will make a piece of wood more stable, and the more impervious the finish the better.
Oiling a fingerboard is something else all together. It doesn't sink all the way into the fingerboard - it penetrates about 1/16" or less into the surface. This provides a layer of protection from gaining or loosing moisture, thus keeping the fingerboard more stable. Of course, when the fingerboard is more stable, the whole neck is more stable. It's not a huge issue, as both Muttley and I have said, but to suggest that it is in any way damaging to the fingerboard is completely untrue. Additionally, the oil you use on the fingerboard is bound up in the wood, and can't possibly effect the longevity of you strings, as if you are playing the way most people do your strings never actually touch the fingerboard (they touch the frets). And of course, none of this has ANYTHING to do with the shit people put on their strings, which I've never liked.
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