Wednesday, December 7, 2016

Gaetano Guadagnini 1831 - A Restoration

I had no previous experience with guitars built by Gaetano Guadagnini II (1805 - 1852) so when Lucas Harris invited me to accompany him to look at an 1831 Guadagnini that was for sale I didn't know what to expect. This photo, taken that day, shows the guitar in nearly as built condition. Only the wooden tuning pegs had been replaced by rear mounted mechanical tuners.  I always thought ivory tuning pegs were archaic.  But here they are, a standard feature on a fairly plain guitar. There was much evidence the guitar had been played for years, but also signs that it had recently been neglected. A few cracks in the top had been repaired - there is a dated repair signature on the underside of the top - but, unfortunately, many more cracks had developed. The top appeared not to have been finished originally in any way and consequently there were several spots that were heavily discolored, I suppose, from contact with the player.  There was also a thick layer of grime.

String length: 640mm
Body length: 460mm
Upper bout: 275mm
Waist: 200mm
Lower bout: 335mm
Sound hole
diameter: 90mm

The maple back is in excellent condition and is finished in a vibrant deep brown-red that is most likely a shellac based spirit varnish. The finish has worn away from the edges of the contour and most notably from the bass side upper bout in a manner that suggests long use by a single individual.  The neck and peg head are ebonized  maple. Note the wear mark from the player's thumb.

The top and back are both strongly arched measuring 7 mm at the lower bout. This degree of arch is maintained at the waist and upper bout. The back also slopes from the tail to the neck joint making the tail block deeper than the front block. Strongly arched backs are not unusual but such an arch on the top is a unique feature. The construction of the arch is also unusual. The soundboard is not domed like Spanish guitars,  but bent side to side from the center line along the entire length of the top. The neck which sits flush with the fingerboard continues along the same plane.

The side ribs are contoured, top and bottom , to accommodate this arching.

The rib height including the top and back thickness :
Neck joint 65mm
Upper bout 63mm
Waist 72mm
Lower bout 69mm
Tail 85mm

Unfortunately these features do not show up readily in the photos.

Let's Get to Work!
Here is a close up of the top showing the major cracks. Others are too small to show up in this photo, but all needed attention.  This work was the focus of my restoration.

Several cracks ran under the bridge and you can see an example under the right arm of the bridge. I thought it was necessary to remove the bridge in order to do a proper repair.  There was already a slight lifting of the bridge at one point so it was easy to slip a knife in the opening. I dabbed alcohol on the knife blade and allowed it to wick into the opening. Alcohol crystallizes old hide glue, weakens the bond and allows the joint to be separated safely.

Older cracks had been filled with shims and several were secured with interior wood cleats. Since there were many cracks to repair it was necessary to remove the back of the guitar. I found an opening between the back / rib joint and wicked alcohol into the joint like I did for removing the bridge.

The back came off fairly easily although there were several difficult moments in the area around the bar ends where they let into the lining. Several bars became loose. Once I had successfully removed the back I finished by removing all three bars.

After one hundred and eighty-four years the back retained its arch free of its bars. I knew it would be some time before I re-assembled the guitar so I made a arched pine form to hold the back. You can see it in the background. The side ribs of any style of guitar have the tendency to change shape whenever the top or back is removed so I made a collar to hold the guitar while it was dis-assembled.

There were several areas where the lining was loose or broken and another location where a bar end had punctured the side rib.

The guitar does not have maple binding around the back. The finish has uniformly worn off the edge of the guitar  exposing the light colored maple.

 I took care of these problems immediately. A simple fix with a spring clamp and a piece of  cork was sufficient in some cases but a two part contoured caul and c-clamps were necessary for others.

It is interesting to note evidence that this guitar was built quickly: the notches in the linings for the harmonic bars ends are too large and the lining for the top is cracked at the waist but not broken through.

This photo shows the external collar that I made to help retain the contour of the guitar once its back was removed. The harmonic barring is a simple pattern as is the shape of the interior blocks. There is a repair inscription between wood cleats in the lower bout.

The harmonic bars are spruce with the grain standing up. They measure 9mm thick and 15mm high and are arched as I previously described.

 Is the date 1928? The cleats from the earlier repair were well done and secure so I left them in place even though I was going to replace all of the old shims. My policy on securing cracks is to use many small cleats with the spruce grain perpendicular to the crack rather than fewer larger ones. Had I used larger cleats this guitar would have had a lot of extra wood in its top which I think is detrimental to the tone. The V is a directional arrow and is an aid to me in placing the cleats.   I clamped each cleat individually using sound hole clamps and plexi-glass cauls. Using this procedure stabilizes the area of the soundboard and insures that the two sides of the crack remain level.  In this photo the cleats are in their rough shape. I left them that way while I fitted and glued the shims. Then I went back and feathered their edges into a smooth low contour.

This photo shows several types of cracks and my treatment for each. Below is a photo of this area of the guitar before I started work on it.

Rather than trying to make a tiny shim to fill a narrow crack I enlarge its width to about .75mm and make the edges parallel. Most cracks occur in the light colored soft wood of the annual rings and are usually fairly straight. The thin dark lines are denser and denote the late summer growth. These harder grain lines serve as a convenient boundary. Not only are they a visual aid but their hardness acts as a 'fence' to guide my knife. Usually I work free hand. There were several wider cracks or cracks that crossed an annual grain line. Because of their width I treat these differently. I use a metal ruler to scribe a pair of parallel lines that are wide enough to encompass the crack. I then gouge out a channel with a veining tool to a depth that is about 2/3 the thickness of the top. This method provides a 'floor' for the shim to rest on and a third gluing surface that provides extra strength for the joint.

I choose the wood for my shims from an old stock of very close grain soundboard scraps and try to match the color of the original soundboard. I can cut very accurate and clean edged shims with my miniature table saw. I bevel one edge of the shim slightly so that it slips more easily into its channel. It needs a good fit but not a tight one. The shim will swell when the glue is applied and it may not fit in the channel. A certain amount of fitting is usually required. I widen the channel a little or narrow the shim a little. When I'm satisfied with the fit I work quickly, brushing a thinned mixture of hot hide glue into the channel and pressing the shim home. I wipe away the excess glue with a hot damp rag, followed by a dry rag and then cover the repair with painter's masking tape to slow the glue's drying which allows the wood to swell a little resulting in a very snug fit.  Everything takes time.

There is still a lot to do, but that's enough for now.

All photos by the author

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