Purfling is the name of the black and white inlay which was traditionally used by most classical instrument makers. Besides its decorative appeal it also protects the plates. By running across the grain at the top and bottom end it can stop a hard impact to the instruments edge from traveling forward into the plate along the grain line as a crack.
Historical purfling shows a wide variety in material, width and coloration.
Different species of woods can be found, maple, pear, poplar, walnut, beech, spindle wood, boxwood, ebony etc. The Dutch tradition was to use whalebone. Makers of the Naples school have often used paper- the city was big in paper manufacturing at that time. Occasionally you see purfling being only scratched in and filled with black ink, the Testore family comes to my mind- it saves time. Stradivari has used poplar for the white middle section and black stained pear wood for the dark sides. The material of choice has an effect on the final look but also on the usability, as the strips are bent into shape like the ribs on a hot bending iron it is nice to work with a flexible material. Ebony for example being brittle makes bending a big challenge and once it is bent and set in it gives a very stiff look to the lines and a strong look for its inherent blackness- ebony was traditionally used by some French makers.
Purfling is commercially available in various materials and thicknesses but I prefer to make my own as to me it looks more authentic. My method is to cut up a thin poplar strip on a bandsaw, plane it down to the desired thickness- this makes the white part. For the black sides I stain pear strips with ferrous sulphate and logwood chips to my desired blackness and glue the strips black-white-black together with hide glue. Once it is dried I cut it up into strips. The width of the black is adjusted at the bench for each individual instrument- I use a scraper and thin the black part down until I like it and/or it fits the model I copy. Thinning them down by hand also adds natural variations in thickness which is most times to be seen in original Stradivari purfling.
The inlay is done by hand, some makers use a purfling dremel to cut the groove. I have made my own purfling cutters, the way they work is historically approved. A hand held shaft with a fixed metal bar which rests against the plates edge- an adjustable steel blade which can be set to the desired distance from the edge and a depth stop to control the cutting depth. I have made two of those cutters, one for each side cut of the purfling groove.
Once the cuts are made for the groove the wood in between has to be dug out. I have two tools called purfling pic for this task.
Before marking out the purfling groove on the instruments plates I like to do a pretest. I use a piece of maple to inlay a pice of my purfling. This ensures my purfling cutters are set correctly, I want to avoid having a groove that is too tight or too loose for the purfling material. I also glue size my purfling groove one time to make sure the grain is saturated with glue before I do the real glue job. This is what the test looks like. I also like to keep this as a reference for the next instrument.
Two photos above of Guarneri del Gesu violins of 1736 and 1740. Del Gesu purfling typically shows variation in thickness and the material used has a soft look and feel to it- it seems to bow to the slight unevenness in the groove.
Below you can see some purfling samples of the Brescian school, a Gasparo da Salo viola and a Maggini violin. Rather crudely made and inserted- matching the rest of the instrument very well- they have their own charm!
Finally a corner of a Stradivari violin. Width and colour of the black strip give a strong impression and nicely accentuate the lines of the outline. There is a little mess in the purfling mitre going on, some black filler being used to fill gaps there. Looking at purfling in detail and close up almost exclusively shows imperfections and mistakes- however from a distance the impression is excellent. A little bit like a masters oil painting which doesn´t make sense when you look at the single brush strokes but is magnificent being looked at from a certain distance.