Re-Hydrating a Classical guitar

[John Yungbluth]

Pleased to present for your consideration. . . . . . . . .

I just picked up a interesting Union Musical Espanola classical guitar at the Goodwill a few weeks ago.  Looks to be hand made.  Solid wood all the way around, spruce top, mahogany sides and back, cedar (?) neck, rosewood fingerboard and bridge, wood binding.  Not a traditional looking Spanish heel, but not a solid rectangle shaped block either.  At the sound hole it looks like a steel string block, but as you move towards the neck , after 1/2 an inch it tappers in and is narrower at the point it meets the sides.  Not a top of the line unit, but not a laminate ISO* either.

I believe she is extremely dried out.  Almost all the top and back braces are pushing against sides. I can either feel the side deforming outward over the brace end, or it is cracking the side.    Around the tail block the side has a ripple developing that has pulled the top away from the side on the treble side. On the bass side the same thing is happening with the side and the back. 

There are no dry cracks anywhere.  There  are little concave areas on the top between the 3 fan braces. 

Slight concave look to the fingerboard down the length.  But it's only under the 3 low strings.  I'll see what happens with re-hydrating. 

Now to my question of the best way to re-hydrate this whole unit.  I have two little units that have a sponge like fiber inside that hang from the strings.  I can make the sponge in the baggie type.  I have a hard case that can latch shut tightly, and have large pliable plastic bags the entire guitar can go into.

What are any recommendations you can share?

Thanks in advance, John

*ISO  = Instrument Shaped Object 

 

[Joshua Levin-Epstein]

I have a classical that has been really neglected as well. I get two automotive sponges, soak them in water, squeeze out the excess, put them in the bottom of a trash bag and place the body of the guitar in the bag, trying not to get the body wet (but I'm not all that concerned.

Hang it somewhere and come back in a couple of weeks.

[Roger Häggström]

When happens after the guitar is treated this way? Lets say it is playable and OK after the treatment, do you need to keep the guitar in a case with a humidifier for ever to keep it moist and in shape?

My guess is that some of this type of hard shrinkage will be irreversible.

[John Yungbluth]

Joshua, Roger, thanks for your responses.

I went with putting the whole guitar in the bag.  Twice I've reloaded the 2 small sponges units I made in the last 7 days.  I've put them inside the guitar body.  The top / side ripple, 6th picture, has properly reshaped.  The back/side ripple, 5th picture, has greatly smoothed out, but still has more to go.

The bottom back rib poking through the side, picture 2, has really changed. The picture shows the extension through the full thickness of the side. You can see the full thickness of the side exposed in the split.  Now things have changed to the point where the split out pieces of the side are moving back more in alignment with the full side.  The gap between the outside plane of the side and the exposed inside plane of the split out pieces has closed up.  It's down to the thickness of the side only being exposed.

The protrusion in the fourth picture is almost completely re-aligned.  The surface split, picture 3, and the small not breaking through bumps from ribs are almost completely back in line.

Now, Roger, my concerns are the same as yours.  At some point it's going to stabilize, and not take in any more moisture.  It will be what it will be. 

Do guitars that have extremely dried out once become prone to repeating.  Do you need to now constantly monitor the guitar?  Even if the new environment isn't so extreme.

Thanks again everyone.

[charley erck]

John, and respondents, I wonder if the majority of the damage is that the body was , overall, smaller by x amount because of excessive dryness/shrinkage, and that the braces, not shrinking much longitudinally, were then too long , and because they were tight to the sides at their ends, pushed through. And, so, going inside and cutting the braces back at the ends,(they seem likely to be loosened up in places, as well), would help future wood movement from causing a repeat of the damage?

A theory, anyway. 

Pardon me if I'm stating the obvious!  Or the ill informed..

[Joshua Levin-Epstein]

In regard to monitoring, relapse and irreversible damage: My guitar's back shrunk towards the center seam, separating from the binding at the waist, and no rehydration will move that. I suppose if I took it apart, it might make a difference but that doesn't seem prudent.

I think the point here is to get the guitar back to somewhat normal conformation and deal with what isn't compliant. You're going to humidify the guitar when the heat is on anyway, aren't you? Well, aren't you?

I think the course of action here is to fix the guitar the best you can and see what happens. And report back.

[John Yungbluth]

Just a quick update on this classical.


I bagged the guitar back on December 8th and monitored it through February 27th. All of the issues with the ribs pushing on the sides have normalized back to proper shape. I thinned out some hot hide glue and worked it into the splits on the sides and they seem stabilized.

Since coming out of the bag I have been moving it daily between the hard case ( that has a sound hole humidifier) and a stand.to see if holds its shape. Here in Nebraska it has been a dry winter. I bought a second digital moisture meter (+/-3) so I can get two readings to figure the average and it s been reading 38%-44% all winter. So far so good. It will have the humidifier in the case until May I think.

I now have a clearer view of what other issues this guitar still has, and I'll start a new thread for those when I bring it back to the bench in a month or so.

Thanks everyone.