TRADE SECRETS

Making purfling

A guide for luthiers who prefer to create their own strips to use in their instruments, rather than buy them ready-made

BY MARIANNE JOST AND SEBASTIAN RIBES Luthiers based in Cremona, Italy

We learnt to make purfling from our masters, Francesco and Vincenzo Bissolotti, and we have continued to use this method for more than 25 years. Making your own purfling could be considered a boring extra task but we actually enjoy it, and seeing the final result brings us a lot of satisfaction.In one afternoon we can make enough purfling for the next couple of years of instrument making.

Depending on the type and model of the instrument, we like to vary the thickness of the individual strips of wood that form the purfling. Here, we describe our procedure of making purfling in a series of steps. Our hope is that this article will be of assistance to whomever tries their hand at making it.

A block of pearwood

ALL PHOTOS FABIO ALESSANDRO RUGGERI

1 This method requires one block of pearwood and one of poplar, both cut to 55 x 5 (tangential surface) x 6cm (height). The pearwood will be used for the stained ‘black’ strips, while the poplar is used for the ‘white’. The length of the blocks allows us to use the shavings for cello purfling as well. The 5cm width makes it possible to plane shavings with a thickness of up to 0.45mm. If we want a thicker strip, we reduce the width of the block.

The poplar, being a softer wood, is easier to plane than the pearwood. We often use 1mm veneers and scrape them down until we obtain the desired thickness.

Making the strips

2 Before each planing, we wet the surface of the wood with a sponge or cloth. We use two well-sharpened no.6 planes, one adapted to cut very finely, while the other is adjusted to cut the shavings. We clamp the pearwood block on to the workbench, and flatten the surface with the fine plane. Then we wrap a belt (such as a Ratchet strap) around the front handle of the second plane, and work together: one of us holds the plane and at the same time directs it, applying constant pressure as the plane moves over the full length of the wood, ensuring that the shaving has an even thickness overall. The other helps by pulling the plane by the belt with force while also helping to maintain its direction.

Checking the thickness

3 We then check the thickness of the shaving with a thicknessing gauge, and adjust the plane blade accordingly. We repeat this step until we reach our desired thickness, while also making sure that the thickness is regular over the entire length.

After planing each strip, we re-flatten the surface of the block before beginning another. This way every shaving will have one smooth surface.

Dyeing the strips

4 To stain the pearwood we use a black fabric dye. We advise using twice the amount of dye to that recommended by the manufacturer for colouring fabrics. If the manufacturer advises 30g of dye per 700g of fabric, we use 30g of dye per 350g of shavings.

We dissolve the dye in boiling water, then completely immerse the strips, ensuring that the entire surface of the wood is covered with water. We monitor the pot for at least 40 minutes, carefully and continually moving the strips around and unrolling them as they curl. We then add a large spoonful of ferrous sulphate (FeSO 4 ) and let it boil for another 40 minutes. Then we let it cool, before rinsing the strips several times in lukewarm water. We take care while unrolling them, until the water runs clear.

The strips ready to be glued

5 To dry the coloured strips we lay them out on a flat surface and secure them with clamps at each end. This way they will remain flat when they are dry.

Next, the pearwood and poplar strips to be used for the upper and lower bouts are glued between two flat slabs of wood. Once the individual purfling lengths are cut out and ready, we bend them to shape with the bending iron.

It is important that the slabs and counterforms used for gluing are made from wood. This helps the glue dry faster, and ensures that it takes well.

Soaping the surfaces

6 We rub dry soap on to the surfaces of the slabs, as well as on to both sides of the paper to be placed between them and the purfling strips while gluing. We never use wax as a substitute for soap as it can create problems later when gluing the purfling into the instrument.

Applying the glue

7 We wet the smooth surface of the black strip with a damp cloth, then immediately apply the glue to its rough surface. We use hot hide glue or slightly diluted Titebond. Both give good results, though Titebond is easier to work with.

Then we apply glue to one side of the white (poplar) strip and place it on top of the black one. We repeat this same step with the second black strip. This process needs to be executed as quickly as possible as the strips have a tendency to roll up (and if you use hot hide glue it gelatinises fast).

The purfling is placed between the paper and the counterform slabs

8 Applying pressure with a damp cloth along the surfaces of the strip will clean away any excess glue. At this point we clamp our ‘sandwich’ of purfling between our paper-lined slabs.

Gluing the C-bouts

Waiting overnight for the glue to dry

9 We make our purfling for the C-bouts using a counterform made especially for each different model of instrument. We cut the strips to the necessary length and, after gluing the strips together, we insert one end into the specially cut slot in the counterform, and wrap the ‘sandwich’ as tightly as possible around it using cotton or linen ribbon. We calculate that the glue adds between 0.05mm and 0.1mm to the combined thickness of the strips.

10a Marking the height with a gauge

10b Cutting the lengths out with a knife

10 Before cutting out the individual lengths to use for the inlay, we wipe the purfling down with a damp cloth to remove the soap along with any pieces of paper which may have been glued on. Then, with the help of a 100 plane, we plane flat the spine (the thin side with the three layers exposed), and proceed to mark the height of the purfling on to both sides of the ‘sandwich’ using a marking gauge (10a). Finally, we cut our purfling strip out with a knife along the mark of the gauge (10b). In the case of the C-bouts, the purfling is cut out while still wrapped around its counterform.

Before cutting out each successive length, we re-flatten the spine with the 100 plane to clean away any marks the marking gauge or knife may have left. This clean surface is the part which will come into contact with the floor of the canal when we finally come to inlay our purfling.

TRANSLATION BY KATE POULTON