Making fingerboards green

With speculation rife that ebony might soon be added to the CITES index of forbidden woods, Alan Beavitt shares his method for creating a fingerboard using veneers rather than full blocks of the wood

Points of interest to violin and bow makers

Two finished ‘conservation fingerboards’

Ebony is the heartwood of various tropical trees, and it takes around 80 years of growth to produce a log of useful dimensions. It is apparent that ebony is being used – especially by instrument makers – faster than it grows, and it is very likely that a CITES ban or restriction on its use will be enforced in the not too distant future.

The largest use of ebony by violin makers is in fingerboards. Synthetic ones are commercially available, but in my opinion there is nothing quite like the feel and appearance of real ebony. I therefore decided to experiment in making fingerboards with ebony veneers that had the appearance and properties of solid ones, using conservation materials where possible. Ebony veneers, or more commonly inlays, were widely used in the Baroque era. Perhaps this was because of the expense, but I think it was more likely for decoration, and to have a hard-wearing surface where it was most needed.

I considered two possibilities for a veneered fingerboard. The first would consist of a veneer on a suitable hardwood base. This would have to be stable and accurately made, as there would not be much leeway for me to make corrections to the surface. So instead I followed the second option, which involved laying the veneer in a mould and backing it with a composite.

I CAN GET FIVE OF THESE VIOLIN FINGERBOARDS FROM A STANDARD EBONY BLANK 

I started with a prepared violin fingerboard with all the correct curvatures, but slightly oversized in width, and made a mould from it. The mould consists of an aluminium tray with a hardwood base, to give stability, and is covered with a mixture of polyester resin and powdered talc, to give a female replica of the fingerboard. I then drilled four holes in the base to promote easy release of the finished structure, using silicone or wax release agents throughout this process to prevent unwanted adhesion.

Then I cut the veneer. My bandsaw has been modified to give a more positive top guide, producing a precision cut, and reducing the need for scraping afterwards. I made the veneer 1.5mm thick, which is about the maximum I can bend, and it allows for a lifetime supply of ebony for resurfacing.

The mould

ALL PHOTOS ALAN BEAVITT

Bending the veneer

Two strips aid the bending process

Trimming the sides 

Gluing the edges 

The mould and components

The bending process involves heating an aluminium tube to 150C, then using dry heat and two strips of wood (to avoid burning my fingers) to push the veneer to shape. I immediately clamped the hot veneer between the concave (41mm radius) and convex (39.5mm radius) formers. I left it clamped up for a while and then trimmed the sides to fit the mould, using a small plane.

For the fingerboard edges I cut two strips of ebony, 2mm thick by 3.5mm deep, and laid them at the sides of the mould on top of the veneer. I glued them using a woodworking epoxy glue (West System 105) loaded with ivory black pigment (no longer made from ivory!) at the rate of 1g per 2.5ml resin, using matchsticks cut to length to hold the strips in position. Then I put the mould on its edge to glue them, one at a time, using gravity to form a fillet at the join.

Vacuum impregnation 

I put two layers of cotton webbing (a convenient source of cellulose fibre), 1.5mm thick and vacuum-impregnated with the epoxy/pigment mixture, to give stiffness to the assembly. To compress the webbing and veneer into the mould, I first took an offcut from a neck-block with a nominal curved surface of 36.5mm, made too high initially for clamping purposes. I trimmed it off at the conclusion to give a glue-friendly surface for attaching to the neck. The second item was a male replica of the undersurface of the fingerboard at the bridge end, made from the polyester/ talc compound and mounted on a wooden block.

Clamping the assembly 

The vacuum-impregnating set-up requires about 40ml of the epoxy/ pigment mix to saturate the webbing, and when cured, has a relative density (1.2) and stiffness similar to ebony. The impregnation should be carried out below 18C to avoid thermal runaway. Then it was time to clamp the components together. The webbing has a cushioning effect, pushing the veneer into intimate contact with the mould. I left the assembly clamped up until the resin was fully cured, which can take several weeks depending on temperature.

Finally I removed the structure, cleaned it up and polished it. I’ve found that I can get five of these violin fingerboards from a standard ebony blank. The savings would of course be much greater for the larger members of the string family.

Although there is more work involved here than in preparing a solid ebony fingerboard, the process lends itself to replication, and it might inspire a manufacturer to produce something similar. We might then be able to enjoy working with ebony indefinitely!