Cello Neck Repain Part 5: Fingerboard Clean Up and Repair

Cleaning the Hide Glue Residue.

I soften the glue with a cloth soaked in hot water. Then I scrape it off with the Stainless Steel ruler.


This is the color and grain of the wood. The traditional black color of ebony is due to a dye that is used to give uniformity to it. Ebony usually has streaks ranging from light to dark brown to almost black.



Here you can see the cleaned fingerboard.


Problems in the Road

The alcohol used for the fingerboard removal took off some of the ebony dye revealing the natural color of the wood. After removing the glue I decided to clean off all the dye and redo the entire fingerboard correcting the problem.
While I was removing the dye with alcohol, I noticed a crack on the surface at the bottom end of the fingerboard. I rubbed it quite hard with the cloth trying to get the tint of the crack, to my surprise two small pieces of wood fell off the fingerboard.


In this picture you can see the length of the crack that runs from the arrow A to arrow B. When I looked closely, I noticed that the pieces had been previously glued with Hide Glue. The residue of the glue can be seen in arrow C.


The affected area must be completely removed and cleaned prior to be re glued. With the heating pad I warmed the area and with a hook type tool pull off the parts.


Solution to the problem, aggressive version

I faced the dilemma of the permanent and appropriate correction for the fingerboard. Apparently the luthier that made the previous fix to this Cello glued the parts with Hide Glue and covered the crack with wood filler. Then he applied layers of black dye to cover the fix.
If I do the same as the previous luthier, most likely in a few years the crack will reappear and the pieces can detach. So I decided to do something that is not necessarily in the books. Remove all the old tint leaving the fingerboard in the raw and cover the whole surface of the fingerboard with two generous coats of epoxy resin. The most obvious question: Why do this? The answer to the question is explained with the procedure for removal of old dye.

Old Dye Removal


With lacquer thinner and an abrasive black sponge I removed the dye from the fingerboard.


After scraping the surface I noticed that the fingerboard had several layers of varnish and dye in the corners. The varnish is the same that was used for the Cello neck. Apparently both parts (fingerboard and neck) were varnished together to give the instrument more integrity.
In the arrow A you can see the black dye still to be removed. In the arrow B a surface layer of varnish, In C another deeper layer and finally the raw wood on arrow D.



In the two previous photos the fingerboard can be seen clean, free from dye and varnish.
The natural chocolaty color of the fingerboard can be seen on the cloths I used for the work. These cloths answer the obvious. Part of the wood was worn with the abrasive sponge.
Coating the fingerboard with resin can return it to the original dimensions and at the same time it will give me some extra material for sanding the surface to its original radius.

Gluing the Loose Fragments


I rubbed the area to be glued with alcohol to remove any trace of Hide Glue.



Here you can see the parts to be glued clean and free of Hide Glue.



The whole area is covered with tape to avoid the resin to fall in the raw wood.


Here are the parts ready to be glue.

The parts must be clamped for 12 hours.

In the two photos above you can see the pieces glued in place. Despite the crack that is visible now it will disappear when everything gets coated in epoxy resin .

Now we just need to rectify the fingerboard and cover it in resin, then re glue it to the Cello's neck.

End of Part 5

3/4 Cello Broken Neck Repair Part 4: Reinforcement

Reinforcement Dowel

On The table saw I cut a piece of Jequitibá or Yesquero Blanco for turning the dowel. I trimmed it to 3 inches long. Once I found the center of the piece I placed it on the wood turning adapter of my drill press.


I round it with a wood rasp and then checked the diameter several times with the Caliper while sanding it to the final size.


The Dowel ended with the same diameter as the wood bit used for the job.



The dowel is positioned at 90 degrees relative to the surface of the neck.


I found the necks center and drill the hole.


The surface of the Cello’s neck should be positioned at 90 degrees relative to the wood drill bit



After drilling I checked the fit of the dowel in the hole. Here you can see that it doesn’t entirely fit in .



I checked the depth of the hole with the caliper.



I checked the depth of the hole and marked it in the dowel to make sure it reaches the bottom of the hole.



I put masking tape before applying the epoxy resin. In the photo you can see beside the dowel, another one wrapped in sandpaper. The dowel has 4 channels that connect from the center of the bottom of it. At the bottom is a small depression that allows the resin to accumulate. Upon entering the hole, air pressure causes the excess resin out through the channels. This usually causes the resin from the bottom out of the hole, running the risk that any other area in the dowel to do so as well, thus compromising the integrity of the joint. The depression allows a build-up of resin maximizing the amount of air expelled and minimizing the amount of resin that is expelled together with the air.



With the dowel wrapped in sandpaper I lower the wall until the dowel entered without applying pressure.



Here is the last dry test. The dowel goes all the way down to the mark that was made with the pencil.



Again, here’s the equipment to apply epoxy resin, gloves and nylon brush.



The epoxy resin is uniformly applied into the hole, I let some drops of it into the bottom. Also I soaked the dowel in resin. Then I slowly push it in with the hand letting the resin and the air trapped inside to go up the dowel channels. Finally I place the clam and leave it alone for 12 hours.
In the first minutes after clamping, the dowel should be monitored because the level of resin in the dowel channels can lower. This happens because the wood absorbs the resin. If this happens, place several drops of resin on those channels until the receding stops.




At the sixth hour of curing the tape is removed leaving the clamp in place. I cleaned all the remaining loose resin around the dowel.
After 12 hours the press is removed. Here you can see the plug, darkened by the absorption of resin.




I cut the remnant dowel with a Japanese saw and sanded it clean with a 220 sanding block taking care not to damage the surface.



This is the final result. The wood is free of resin and ready to receive the fingerboard, thus completing the assembly.

Now we just need to clean the fingerboard and prepare it to glue it back to the Cello.

End of Part 4

3/4 Cello Broken Neck Repair Part 3

Gluing the Parts


This is the epoxy resin used for the repair.

West System is a two-part epoxy resin that cures at room temperature as a high-strength plastic solid. The resin is mixed with pre-calibrated pumps that administer specific proportions of liquid epoxy resin and hardener. One squeeze of each pump, resin 105 and hardener 205, make 8 ounces of mix material. This resin is highly resistant to moisture, it adheres to a wide range of materials, making it ideal for projects requiring chemical resistance and impermeability. The strong physical properties of this epoxy resin makes it ideal for coating and structural bonding. Its low viscosity and penetration properties make it ideal for use in wood, fiberglass and metals. Since it doesn't shrink it is used to fill cracks. It is sandable and compatible with all types of paint or varnish.



The cello waiting for its fix.

I covered the entire edge of the area to be glued to prevent damage to the varnish by the epoxy resin. After the resin is mixed, it is applied uniformly with the fan brush. Both sides to be glued most have resin and should be left with it for at least a minute to be sure that the wood absorbs some of it. More resin should be applied before joining the two pieces if necessary.


The two sides are joined with two clamps until the resin cures and hardens. The resin cures and hardens in about 10-12 hours. All resin squeezing out of the joint drips on the tape not on the varnish, making the subsequent finishing work easier.



After about an hour I to turn the cello upside down so the resin can move to the large empty space filling the crack. With a brush I applied a bit more resin to fully seal the crack.


Here you can see the good coupling of the parts

I removed the tape at the 6th hour of curing, when the epoxy is in a rubbery semi solid state.
I recommend doing so at this moment because once the epoxy resin cures, the tape becomes extremely difficult to remove and very probable you'll need a chisel or sharp tool to do so.
At the twelfth hour the resin is cured, now we can remove the clamps. For extra precaution I removed the tape and let the clamps on for a period of 24 hours.


The loose parts were all joined together without any trouble.

Now we need to built a Dowel for the reinforcement.

End of part 3

3/4 Cello Broken Neck Repair Part 1

Well, here is my first project of this blog.




This is a Rolf Meister Luthier Cello, Model SC-100 3/4 size. It arrived to my workshop with a broken neck.

Neck base, body of Cello. You can see how the soundboard is attached to the base of the neck.

Neck break.

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Before I began, I got the two parts together to see if the pieces joined well.
To my dismay what I saw made me realize that the break occurred a few years ago.



As you can see from the photos "arrow C" besides being broken, the neck suffered several additional blows after the break, both the base of the neck and the headstock. These blows crushed the wood and also caused the loss of the wood chips from the break. Over time moisture levels in the air expanded the wood fibers leaving a small crack in the join.

In this picture you can see how the fingerboard got unglued from the blow and caused a crack in the wood of the neck. The headstock has a blow that crushed the varnish almost to the point of chipping it. In the photo above "arrows A” the unglued fingerboard can also be seen.


In the "arrows B" of this and the previous photos you can see the varnish cracked by the force exerted by the break.


From what can be seen I understand that this Cello did not suffered a common fall, rather someone dropped something heavy on top of it. As observed in the cracked varnish, the neck broke in the opposite direction to the tension of the strings. This lets me know that the Cello strings were not set at the time of the accident.

There are a number of small bumps and scratches all over the body of the instrument, mostly cosmetic; in its time I will correct them. Very likely those were accumulated trough the years it was stored. For now the important thing is to attach the neck to the body and strengthen it so it will not break again.



End of Part 1