I set out to do a normal neck reset on a 1940's L-00 acoustic. Ued a heater blanket to soften the neck extension and used a spatula to release the glue. Took off the 15th fret, drilled a hole for my steamer needle, put on the neck removal jig, heated up the cappacino maker to the steam stage, inserted the needled and had a million rags ready to sop up the moisture. No problems so far! Well, this is where it all went south.
The neck joint wouldn't budge,even after about 10 minutes of steam! I was frantically sopping up moisture from the steam around the fretboard extension, but as you can see, it dulled the finish, yellowed the black color between the fretboard and the soundhole, and turned the finish white in some spots on both sides of the soundhole on the upper bout...what the heck is that?! The steam also shot out of the truss rod channel on the headstock and before I realized it, it had bubbled some of the finish a little and dulled it. And to add to the frustration, the finish was softened the heel cap and came off with the caul I had between the fixture and the heel.
And the neck joint still didn't come loose! Is there something unusual about this neck joint on this model? Any suggestions on how to get the neck off and repair the finish damage, aside from a refinish? Any help would be greatly appreciated!!
I would bet you dollars to doughnuts that the neck was set at the factory, then the top glued on, then the fingerboard glued on. I've seen other older Gibsons that way. You'll have to cut the fingerboard extension off where it meets the top. Then cut out the top to allow the dovetail to come out. Of course after you get the neck angle corrected and reglued, you'll have to piece it all back together again.
I doubt the white stuff was mineral stain. When you boil water, the minerals tend to stay behind, and what you get is steam, which condenses into, you know - distilled water.
That said, I get those white marks sometimes on lacquer, and I use a little trick I learned from Greg MIrken - a VERY quick and light wipe with alcohol. Works like a danged charm, I tell ya.
Another very useful tip is to drill two steam holes - one for "in" and the other for "out. Really cuts down on the mess.
I'd remove the fretboard extension, as already mentioned, but I'd severe it at the 13th fret so you have an overlap at the body joint to add strength. Once the fretboard extension is removed you can see the joint better. It has a dovetail joint and you will be able to steam it off, sounds like you may have more water in the steam than you want. I use a medium size pressure cooker for steam, with only about an inch of water and a short steam hose and I get mostly steam.
Once the neck is off you can repair the finish by spraying a fine mist of denatured alcohol or lacquer thinner on the damaged finish, it will renew it. On the older guitars, once the finish is dry, I would then give it a light buffing with 0000 steel wool, with the grain.
All replies are right on. Did you by chance look inside at the heel/joint area to see if someone over the years had put a screw in it ( years ago the neck may have been a bit loose, and the owner placed a screw in it to secure it tighter).
Also, did you score around the heel to 'break' the lacquer?