Humidity and Glueing Neck to Fingerboard

[Darryl Young]

The humidity can make a big difference when doing some glue operations. Glueing the cross grain braces to the top and back comes to mind as a good example. I glued these joints with the wood stabilized around 40% humidity.

Since I'm building in my home, I don't have a humidity controlled environment. So I'm curious how much difference it makes if I glue the fretboard to the neck at say 50% or 60% relative humidity? Could it cause problems when the humidity drops in the 20% range in the winter? It's not a cross grain joint, but I thought I would still ask. If needed, I can place the neck and fretboard in a large ziplock bag and bring the humidity down just under 40% using silica gel and then do the glueup.

I recall a post that listed all the glue joints that needed to be made when the humidity was low......and the ones that it really didn't matter much, but I can't remember where that post was made. Anyone else remember that post?

[tippie53]

Humidity during glue up can indeed cause some interesting things to happen. I like to stay 45% in my shop. It is good to consider RH during the build.

[klooker]

If the neck & fingerboard are both stabilized and have been kept at the same relative humidity, humidity shouldn't make any difference assuming they are at a relative humidity level that the guitar will experience in it's life.

Kevin Looker

[tippie53]

if you glue up something and it gets exposed to a rh of a significant higher or lower RH , cross grained wood can move.

[klooker]

In the case of gluing a fingerboard to a neck, the grain of the 2 pieces is parallel so there are no cross grain issues.


Kevin Looker

[Tony_in_NYC]

But they are two different species of wood and two different thicknesses.
I have read many a guitar building forum in my day,(my day being Tuesday of last week) and there are certain things people do in controlled humidity, like bracing the top and back, and certain things where humidity matters less, like kerfing the rim.
I would imagine gluing the neck and FB in a higher humidity environment wont be too problematic. The issue with gluing the fretboard to the neck comes with the water in the glue. You don't want to use too much glue and cause the FB or neck to warp, but you still need enough glue to ensure a good joint.
Ken Cierp has a picture on his site showing the FB to neck gluing procedure and how much glue he uses.
Thats probably a good place to start.
FYI: I probably wouldnt listen to me if I were you. I have only built two guitars. However, in 9 months, neither has fallen apart. On the other hand, I have read Cumpiano's book, so I am probably an expert luthier, right? On second thought, listen to everything I say. I am awesome! LOL

Disclaimer: The part where I say I am awesome and an expert luthier are totally jokes. If anyone thinks I am even remotely serious, they are dumb and probably should wear a helmet when walking to prevent additional head traumas to diminish their already small mental capacity. Thank you.

[tippie53]

I have seen ebony warp off a mahogany neck. The few times I have seen this happen , the ebony was not well quartered and the water in the glue expanded the ebony. This didn't have anything to do with RH at the time of glue up.

[Tom West]

Darryl: You stated in your post that you did your brace gluing at 40% RH and asked what would happen if you glued your fingerboard at 50% to 60%. Actually I don't think you would have much of a problem,but I would prefer to do it at your 40%. Then I think you run into trouble. You ask what would happen to the fingerboard when it was exposed to 20%RH. Again I think your finger board may be OK but the rest of the guitar will be in a mess of trouble. I'm certain you did not mean that you exposed your guitar to this and were just trying to point out that RH drops of this extent can cause problems. Not trying to rain on your parade but just trying to point out to some of the other newer builders the importance of proper RH% control. Don,t want folks to put a ton of work into a guitar and then have it crack due to not being aware of RH% requirements. Take care.
Tom

[enalnitram]

Darryl also asked about an old post where glue joints were listed that weren't as critical when it comes to humidity...and I'm curious about this too. I'm in the same boat as you, Darryl, I have a hard time controlling RH.

[tippie53]

RH control is as important as anything else. I like to do gluing around 40 to 45%. 50% is okay but once you go past 55-60% you will be in a gray area. This can cause funny things to happen in lower RH. Now if you live in AZ you seldom see about 40%.
Try to work in an avg RH for your area. If you are along the coast your rh will be higher than if you are on the plains.