by Michael Lewis » Fri Dec 04, 2015 4:12 am
Trying to get your steam needle under the fingerboard is quite likely to blush the finish. If it is lacquer it can be fixed, but if it is a varnish finish if you blush it you are . . . . well, just say it becomes a bigger mess.
You need to separate the fingerboard before applying steam to the dovetail. Careful work with a putty knife is most likely the answer but each job can respond so differently from the next. Most likely you are dealing with hide glue, so there are two ways I know of approaching this. Heat and moisture with a hot putty knife where you have a pot of boiling water and at least a couple putty knives and keep changing them to get heat and moisture under the board, which is risky to the finish; and then there is alcohol, which also can be risky to the finish. Alcohol is how violin and bass fingerboards are removed, as it sucks any moisture from the hide glue and breaks down the bond. A blade is slipped under a corner, a drop of alcohol, wiggle the blade, add another drop and wiggle, etc. always following the seam. Repeat as needed.
It really helps if there is some gap already that you can exploit, otherwise you have to make the gap. Be careful, gentle, and firm.