Gluing the linings with counterforms and springs

An efficient method for a complex process, which allows freedom of movement

The modelling of the ribs defines the shape of an instrument’s body, and gluing the linings makes the structure perfect. Using an internal mould with counterforms allows for the step-by-step modelling of the violin outline, as well as fine adjustments, from the construction of the mould to the gluing of the linings.

When I start the gluing, I use counterforms that I design and cut at the same time as the internal mould itself. This method gives me pinpoint precision and control. I like to use a stable support, and the firm ribs permit good speed of execution. In addition to the counterforms I use springs as clamps. The ones I’m using now were made by an old artisan who works with steel, but the traditional method at my school was to use mattress springs cut in an open ring. To do this, you need to find an old mattress, extract the coils, and cut them into many rings. The best springs are those made with high carbon steel and a diameter of around 3mm, as they offer good elasticity and mechanical resistance.

I learnt this method from Renato Scrollavezza at the Parma Violin Making School and I still use it today, practically unchanged.

The mould and counterforms are drawn on the wood

1 I design the counterforms while building the internal mould itself, so I’m always careful to leave a good amount of space to draw them on the wood. For a violin I use a marine plywood board, 450mm long and 330mm wide, with a thickness of about 12mm. First I draw a centre line on the board, and then to draw the mould I secure the template in perfect alignment with the centre line using drill bits. When this is done, I draw the external contours of the counterforms freehand (the internal contour is given by the cut of the mould).

2 The finished counterforms must be about 40mm wide, to match the openings of the springs. I draw them just slightly larger to allow for the bandsaw cut.

Mould and counterform

I number each counterform with a Roman numeral, and to remind myself which side is which, I add a dash below each number on the back side.

3 Now I use a bandsaw to cut out the mould and counterforms. Then I smooth them using a sandpaper roll and finish the curve with a medium-cut file. As the template is the reference for the mould, the mould itself will become the reference for the shape of the counterforms.

Smoothing a counterform on a sandpaper roll

4 The counterforms are almost ready, so I proceed to build the rib garland. When this is done, I fit the ribs to the mould to test whether the counterforms adhere perfectly to the outline. Then I can go ahead with bending the linings.

How the mould and counterforms are looking

Checking the curve against the rib garland

5 Now I put the linings in position. To protect them against the inevitable clamp marks, I use a resistant but flexible plastic with a thickness of 10mm. A plastic chopping board cut into strips works well; waste linings can also be used, but I prefer plastic because it is more adaptable.

Clamping the linings

A plastic strip protects the wood

6 For the springs to work well as clamps, they must have a light resistance.

The diameter and a good steel quality are the keys to effective springs. If the opening of the spring is too wide you can reduce it with the palms of your hands.

Detail of a lining in position

7At this point I check the rib garland, and if everything fits properly I start removing one lining at a time. I glue it, clamp it and carefully clean off the residual glue with a damp piece of fabric. To prevent accidental gluing you can put a little layer of soap on the counterforms.