Violin Forum/Message Board

[John Cadd]

The two most common reasons for Purfling are (not in any particular order ) Decoration and Physical Protection against knocks and splits. All good so far . But I was working on a Telesforo Julve guitar last week and needed to replace the edge Bindings which had been damaged. The bindings were Maple strips and inside those was purfling .It was wider than violin purfling . The connection of the top was interesting as the traditional triangular wooden blocks were well spaced apart . Nothing too unusual so far. The blocks were also very open grained . The third feature I noticed about the binding was the way the edge meeting the sides was bevelled so that there was a minimal glue contact against the top of the sides . Much of that edge ended in a knife edge. To me it seemed the maker was trying to achieve a minimal rigidity in the top connection .
Now from Violins through Guitars we move to Pianos .In a Piano the strings can create inharmonicity because of rigidity where the vibrating section ends . The ends of a string for a short distance do not fully respond as freely as the rest of the vibrating section resulting in Inharmonicity .
Can I assume that a violin and guitar plate (or top) will behave in a similar way as the vibrations reach the sides ? Now back to Violins as made in the Late Stradivarius period .If you imagine four lines drawn from the bridge feet , outwards to just avoid the top and bottom tips of the soundholes and ending at the edges of the plate . The area outside the soundholes was made quite robustly by (late) Stradivari . It has purfling all around the edge but there is solid plate contact at the corner blocks . The edges of a violin plate are protected (in a useful way ) but the purfling creates a weakness as well . If you wanted a strong connection in a wood joint you would not cut into the wood and insert purfling merely as decoration . The purfling has a deliberate weakening effect to reduce edge stiffness . Some Xrays of Stradivarius violins show gaps below the purfling . Not consistently but there were gaps . I also noticed gaps below the Guitar purfling . So edge stiffness and strength was not the main aim when inserting purfling . Certainly not in the Julve guitar . The glue was mainly applied to the lining but hardly any to the guitar body . It was minimal gluing whereas other parts showed the usual squeezout lines . In the late Stradivari violins the edge weaknessing works perfectly in the areas in direct line from the bridge feet . Violin and Guitar edge stiffness and piano string end stiffness are best avoided . (It seems ). I expect some reflection of vibrations would rebound across the top plate which will improve resonance . Maybe we can enjoy the idea of Stradivari working that idea out so long ago .

[Michael Darnton]

I believe that it was in the 1970s or early 80s that someone got the idea (and published a paper about the results) to cut a "purfling" groove around the inside of the violin just inside of the linings and blocks with the idea of freeing the top somewhat similarly to the way you are suggesting. It looked just like you might imagine, but being on the inside no one would notice.

I'm sorry I don't remember the results. I think it may have mainly been greater volume. I don't remember if they stated the tonal change.

I don't remember where the study was printed. My top suspects would have been the VSA Journal or the Catgut Acoustical Journal.
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[John Cadd]

I was interested in similarities between the violin and guitar . The "weakness" is useful in the same way a fuse is useful in an electrical circuit . The weakness is the protection . Having the purfling fitted deflects the damaging forces by mainly crossing the belly grain . One guitar contributor seemed to dislike the gaps between the blocks as it would let glue dribble through the gaps . Obviously he has not considered the drawback to having a solid rim glued all around . Torres left no gaps at all so there is a good divergence of methods . I used a similar method suggested by a violin repairer to remove the linings. There was very little varnish on the linings and I taped on rolled up strips of paper tissue (toilet roll paper) this only contacted the lining itself. Small gaps in the tape allow wetting which slowly seeps through the wood overnight . I covered that with a strip of cling film . Next day the lining released very easily .A thin blunt knife peeled the lining away with a gentle wiggling action .The old glue quickly hardens again as air gets at it . Guitars are built in a different order than violins . A violin top with belly blocks would need to be fitted before the back I expect .

[John Cadd]

The forensic approach to understanding why the guitar binding had been bevelled internally seems to fit my basic conclusion that a delicate edge connection was being aimed at. Blocks or Peones with wide open grains ,and well spaced apart . Minimal glue on the guitar itself. but more on the bindings .And an almost knife edge touching the side tops .
I had not imagined altering the design of a violin but if you had to try it would affect the violin lining strips . The length of the soundholes would cast a shadow radiating outwards to where the corner blocks live . No alterations needed there . The normal linings give the sides some stiffness so just the top edge could be dropped down about 1/8th of an inch Then insert very small softer wood blocks (spaced out ) to attach the belly .The area around the corners would be left intact with normal linings .Weaker glue as per normal would hold the top in place . Can you feel the itch to try some balsa wood here ?
Some Strads bellies had a thicker strip across the plate level with the top block to maintain the neck angle against string tension . Did that element die out again ?

[Michael Darnton]

You might find it interesting that several times I have had a violin top almost fall off in my hands while gluing a loose seam. I pry open a bit to get the glue in and like a zipper a full bout or a side, or most of the top comes loose even though I'd already checked all around and it was definitely closed. Apparently the rib was glued so an opening wasn't visible, but the lining behind wasn't, or the glue joint was weak and starting to open.

One time I was dealing with a viola that had been to a number of shops without cure and so I just opened and reglued everything that I could pry loose, even if it appeared glued. The tonal problem of several years' standing was completely fixed.

When I get these situations securely glued up, players have 100% indicated to me that the sound is much improved, so I'm inclined to believe that a secure connection here is necessary on a violin.
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[John Cadd]

I am firmly in favour of glue joints being secure .I mentioned on a guitar site ."These guitars work much better when they are glued together properly ". On violins dry clamping first then releasing a few clamps at a time to work around seems safer . A plastic improvised spatula does not draw heat away from the glue as it is applied .I don`t like the "paint it all round then place the belly on "method .Having the loose plate at the bottom avoids dribbles too . I don`t know how it`s done normally .

[John Cadd]

The Julve guitar had those three features at the edges .Spaced out blocks , wide soft grain blocks and bevelled bindings on the inner edges. None of those happened by accident .I find the tone of Julve guitars quite distinctive so thought it might be affected by those intentional features ,
Not especially connected to the late Strad violins apart from the "robust" middle bouts .Is that noticeable or just an urban myth ?
Some features might be tried experimentally by makers but have no effect. But improvements in sound could be made accidentally when the reason for the change was to streamline production . That could become lost (or never realised ) information .

[John Cadd]

The little mystery about bevelling the inner edges of guitar linings looks more like a practical way to avoid glue dribbles between the separated block. By bevelling the edge the glue application does not need putting on two separate edges ,The bevel is close enough to the edge without extra contortions and any dribbles would be kept to the side . Whether it makes any difference to the sound is hard to tell .I think the practical aspect is a good answer to my question . Julve was very neat and tidy with his gluing although some squeezeout was left alone for all to see . I don`t recall seing squeezeout anywhere inside violins . Not in photos anyway .