lbpesq -
Polymerization is when molecules that are short in size organize to form long chains of molecules. This is how plastics are made - relatively short petroleum molecules which would normally be volatile (like solvents or gas which evaporate rapidly to fuel oils that leave a sticky mess for a long time) are chemically combined to make macromolecules that have very different properties like increased strength or water resistance.
Any oil will penetrate into the wood when you put it on, but most of them don't harden very much. Something like tung oil will polymerize by itself when the solvent it's dissolved in evaporates. For whatever depth it penetrates into the wood (I think we're talking just 1/32 or so) the wood surface will be *really* hard - more resistant to scratches and passing less moisture through as well. I believe linseed oil also does this, although it needs to be boiled (and probably some other processing) for it to harden.
If you use something like lemon oil (as discussed before, we're not talking about lemon juice or lemon-scented liquid furniture polish), it will soak into the wood and that oiled surface will cut down on moisture coming in or out of the neck wood. But I don't think it will harden into a protective coating at the level like tung oil. And the amount of humidity protection will probably be less than a good coat of wax.
If you expose your neck to hot, dry conditions you really will cause the moisture in the wood to migrate out. If you're unlucky, that will cause the wood in the fingerboard to separate along the grain lines and you'll get a split. So an oil finish, or a coat of wax, or even dousing the neck in a non-polymerizing oil will probably help to some extent. But you really need to avoid the dehydrating conditions (as they say, if it would be uncomfortable for you, it will be uncomfortable for your bass too).
On a $300 guitar, you may have cracking problems because the neck woods were not fully seasoned, which means that they had too much moisture in them when the neck was built. When the moisture migrates, the fingerboard may split. That's probably not a problem on your Alembic since the shop really knows what it's doing, but Alembic does build with a lot of exotic woods which can be more sensitive (ebony, cocabola, and burled woods, for instance).
For most people who's instruments don't have harsh environmental conditions, I think that dirt and dust collecting on the fingerboard is a much bigger threat. Your hands have oil and perspiration on them. The oils you leave on the fingerboard and frets attract dust and the dust is quite abrasive on the fingerboard and frets. So keeping them clean should be a priority (even if it's sort of gross and not much fun). Something like lemon oil is a good cleaner for this goop.
The oils from your hands are what a chemist would call polar. THat's why it's hard to clean oily things with just water, which is non-polar. You can clean them off more easily with a non-polar solvent, and lemon oil is one example of a gentle one. You could also use a stronger solvent like naptha, but a stronger solvent will also attack that polymerized oil finish on your fingerboard, so you're well served by using the weakest solvent that will do the job. And I think lemon oil (or the smelly solvent in my German wax) does a pretty good job of that. And, just like your car, having a good coat of wax there probably wouldn't hurt either.
Finally(!), you asked about where all those lost polymers were going. After this long post, you've probably figured out the answer already (if you didn't fall asleep along the way). Mostly what's coming and going is the humidity/moisture/water in the fingerboard which you'd like to keep stable. There's (probably, but I'll wait to hear what Alembic says about whether they give a finishing oil coating to the fingerboard during construction) a very thin polymerized oil finish protecting the surface of the fingerboard which you are wearing away as you play in areas where your strings and fingers are touching the wood.
That last part is kind of important, since you can think of your finished fingerboard sort of like a balloon. You only need to puncture the protective surface in one place for what's inside to start leaking out. Now, the wood finish is an intentionally leaky membrane so this isn't like a balloon popping and there's already a lot of holes in it like the fret slots. But if you have a lot of fingerboard wear (more likely on guitar than bass) then you're really much more exposed and really could benefit from wax if not refinishing.
Of course, I welcome comment and correction from any and all, especially the Alembic folks.
David Fung
