Gaetano Guadagnini Restoration - The Conclusion

    

Here is a photo of the Gaetano Guadagnini 1831 guitar after I finished its restoration. In my last post, after a brief introduction and a description of its condition, I used nearly the entire post to demonstrate and explain the internal blocking and shimming of the numerous cracks in the soundboard. Since there were so many cracks I couldn't help but wonder whether the guitar would regain anything of its former character. My goal was to return this interesting and important instrument by a member of the famous Guadagnini family to its rightful place on the concert stage in the hands of a fine musician.

The bridge is not only a prominent feature of the guitar it is also an integral part of the barring system of the soundboard.  The bottom of the bridge is contoured to fit the high arch of the soundboard and its unusual size (225mm x 14mm x 20mm) stabilizes the soundboard arch and moderates the soundboard vibrations in the same way that an internal bar does. I needed to take particular care in re-gluing it.

  

Clamping the bridge was going to be difficult because  pressure would be exerted unevenly on on the front half of the bridge leaving the important rear gluing surface unsecured. I devised a caul to solve this problem. Bridge clamps placed through the sound hole could now be centered on the caul. Others clamps were placed on the bridge wings. An arched  caul provided necessary support internally. Clamping pressure was exerted equally across the length of the bridge ensuring a good bond.

Now I could turn my attention to the back. I had taken the three bars off the back and those had to be carefully replaced in exactly their former location. I had previously marked their location so that went smoothly.

Even though I had retained the guitar in a collar (see previous post) in an attempt to keep the contour of the side ribs stationary they splayed out slightly. When I tried to align the back it no longer fit. I wasn't completely surprised. The bass side rib bowed in slightly at the waist but out at the upper bout - a perplexing and difficult situation. I wasn't convinced that normal clamping pressure would hold everything in the correct alignment so I made a special clamping jig that spanned the width of the upper bout.

On the treble side upper bout it fit flat against the side rib and was held in place with a vertical screw clamp.

The bass side of the clamp was made to exert pressure near the gluing joint. This arrangement pushed the side rib into alignment while the neighboring clamps held the joint together.

You'll notice that the wooden clamp feet point in different directions. I made the clamps this way on purpose. The feet fit more or less loosely on the screw rods allowing each foot to conform to the any arched surface. Turned sideways the foot is more rigid and less of its surface is in contact with the subject.

It was clear to me the gluing operation would take a lot of time. Too much really so I decided to do the work in stages. First, I clamped everything in position without glue. Then starting at the neck joint - this ensured that the proper neck angle would be preserved - I released a few clamps and inserted hot hide glue with a brush, knife or artist spatula.  Once the clamps were re-applied I moved along to the next area, one side then the other. I treated the upper bout, waist and lower bout as separate areas. The technique worked almost perfectly. There were several minor areas where the back overhung the ribs. Whether the back or sides changed shape or shifted or I erred is difficult to know - probably a bit of each.

Originally, the peghead was fitted with wood tuning pegs but these had been replaced at an earlier date with mechanical tuners as shown.
The peghead angle is 20°.

I removed the metal tuners and plugged their  holes as shown. The holes for the posts of the metal tuners were different than Guadagnini's wood pegs so there was some over-lapping of holes which I thought might cause problems. To avoid this I laid out a slightly different peg spacing in order to avoid drilling through an area that was already weakened by over-lapping plugs.  Also, the gears on the metal tuners were mounted with protruding lugs that left deep ugly holes in the peghead wood. I filled these with a mixture of fine ebony filings and cold fish glue.

I sanded the rear of the peghead smooth and refinished it with shellac dissolved alcohol blackened with aniline dye. The end grain of the wood plugs resisted the new finish and many applications of the shellac solution were required. I used a chisel tipped artist brush to build up enough thickness of polish that could be levelled. Then I switched to a regular French polishing technique to finish the job.

The photo is of the finished peghead. The tuners are a planetary type peg.

Although I had finished all of the major restoration work there were a few things to tidy up. Two of the inlaid ivory frets were broken with fragments missing (the 9th and 11th), so I decided to replace these with ones I made using bone saddle material. I also levelled the frets and re-crowned them using typical fretting tools.

I did not clean the top before I started working on the cracks because doing so would have forced grime into the open wood, staining the edges of the cracks and making the subsequent shims even more obvious. Cleaning the top was part of my plan to blend the lighter color of the shims with the original color of the top. I dampened a new shop rag with water as hot as my bare hands could tolerate, wrung it out quickly but throughly, and wiped it over the top. Then I burnished the top dry with a wool polishing cloth. Since the wood I used for the shims had darkened with age this final procedure produced a good looking aged patina.

Note* I would not have used such hot water had I not been sure that all parts of the top were sound and secure.

After I finished re-gluing the back a few areas overhung the side ribs as previously mentioned. Levelling these with the side ribs removed the original finish. In this photo the finish had worn off the bass bout through years of playing. Since that was part of the guitar's story I left that alone as well as other wear marks. Closer to the neck was an area that my work disturbed. I renewed the finish by making a thick glaze that could be brushed on the bare wood in one coat.

Glaze was applied to the edge of the back in this area too

I mixed about a 3mm length of burnt sienna oil pigment squeezed from the tube with an equal amount by volume of spar oil varnish and several drops of cobalt dryer. I brushed this on with as little overbrushing as possible and allowed it to dry for several days. Then I sanded out any heavy brush marks with 600 paper and applied a thin wash of a shellac solution.






That finishes my description of the restoration of this splendid guitar. Here are two final views.

*****

All photos by the author.

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
   
                                                                    *******