Not an answer, just my 2c, but I'd be reluctant to oil the FB right now. No matter how well the crack has healed, oil will get into that crack and (a) probably make it more visible (depends on the wood) and (b) make it tough to glue effectively if you need to go down that route later.
Hey Luke: I would let the instrument stabilize in decent, room level RH. Inside the bags at our place measures about 75% so it's likely that the crack will open up again but that's what you want if it is going to open up anyway. You want it open for you so you can wick in thin CA and sand with the grain (220 is good) immediately letting the board dust fill the crack. I usually repeat once or twice and then the crack is invisible, stabilized in it's open state, filled and glued.
Oil is a bad idea until after this is done, the crack is filled and invisible. Personally I prefer Howard Feed-n-wax for boards after hitting the frets with OOOO steel wool to shine them up too.
Lately we have been treating top cracks the came way. Sure we can force them closed but is this always a good idea? That was a rhetorical question...:) So these days after dehumidifying we often let the instrument stabilize for a few days and then fill as needed be instead of forcing a crack closed that does not want to stay that way. Our belief is that other cracks that may have happened in the future are less likely to even happen if we let the instrument assume it's natural state in normal RH prior to the repairs.
Yeah, no need to remove the frets just so you can sand between them and right up to them to get dust in the wet glue making a filler of sorts.
I do a lot of set-ups... an understatement with over 20 of them last week alone... and it's not uncommon for us to miss things in the initial evaluation of the instrument while the client is present. From nut slots that are too low, cracked fret boards, etc. these little scope creep items if we don't catch them up front we simply fix them at no additional charge. Mind you this is for the little issues not say loose braces, structural cracks, etc. then we go back to the well with disclosure, a plan, a quote and seeking authorization to expand the job as need be.
Anyway during set-ups it's not all that uncommon for me to notice a fret board crack and then I simply do as I have described above, takes 3 minutes or so, and usually we don't even remember to mention it to the client and they certainly are not billed for it either.
The same holds true for hairline cracks in bridges spanning the pin holes. I fix these the same way, CA, dust, sanding, and crack gone.
So you are right Luke no need to remove the frets. My experience has been that after filling and then cleaning the board and frets with OOOO steel wool (completely shielding any pups if present with 2" masking tape and vacuuming up the debris from the steel wool immediately afterwards) that the repair becomes invisible. Add Howard's to pop the figure of the board and call it a day.
I like this approach to cracks, Hesh. I've had too many cracks that reappear down the road. (I think I may see this a bit more often than others may because it takes me forever to get anything finished.) It makes sense that this would be the case since the crack probably indicates tension in the wood that 's been there from the beginning. I usually splint cracks like this but I'll try your glue and sand process for small ones next time it come up. Thanks.
Exactly and when and if a client's instrument cracks again I want it to be a new crack that results in revenue and not an old crack that results in a redo or refund.
Perfect world would be that they heed the information that we always provide about hygrometers, humidifiers, and not only leave the shop with an Oasis humidifier in hand but actually use it.
We tell folks as a rule here in Michigan that if your furnace is on your ax may need to be humidified.
I've fixed so very many cracks in the last 3 - 4 months that I feel like a proctologist.... :)