Violin Forum/Message Board

[John Cadd]

If a back has come apart the job of joining them without uneven edges can be tricky . Holding the two halves together with brass straps is the best start . To make the edges line up you need to think how you interlock your fingers .
Along the inside surface glue a series of wooden strips .Each strip is glued on one end just away from the edge.The other end pokes out .Arrange these strips alternating all along the edges . As they are brought together the "interlocking finger " action keeps the edges level .
The brass straps will need some room in between the strips. Once the glue has set all the strips can be cut away or the glue blobs softened with damp tissue (covered with cling film for a few hours .)
That works for a straight join. A back join can develop a wavy shape which needs a little careful surgery .
Maybe after getting the lines to match
( Unlikely to be perfectly straight )it might work better to use Araldite for any gaps . The back is not meant to come apart again.

[tyrionlannister]

[John Cadd]

What type of wood --in a violin back ?? You must be from a guitar background .Maple is the only wood used for backs . I used a similar method for a full size guitar but without any brass straps . I improvised wooden blocks along the join with wedge type clamps .All very home made . The guitar back was Brazilian rosewood so it was too good to throw away . The curvature at the break means you need to do a few dry runs to make sure the wooden strips are not altering the shape. Careful inspection of touching surfaces shows up problems . The edges must be checked in case there are splinters .Mostly the violin back edges are intact but glue has to be cleaned off before reassembly .That is any original hot hide glue.Unfortunately amateurs use bottled Cold Hide glue which can be stuck to the edges , Sometimes hard rubbery glue can be there too .It`s amazing the awful things people do to violins. Cold bottled hide glue will shift with a steamer.It turns white like chewing gum. It never dissolves though .You have to pick it off sometimes with your fingernails . Don`t hack away with anything sharp on the edges .
When poor quality repairs have been done the "repairer" will try to squeeze the wrong kind of glue into the seam . So the advantage is they will not have been careful enough to remove the traces of old H H Hot HHHide glue .So a steamer can get lucky and shift all the rubbish because the base layer is still dissolvable .
Guitar people in their wisdom prefer using domestic irons to burn everything away or melt it .The steamer heat is instantanious and the hottest temperature lasts for a second or less .
If you don`t like using hot hide glue --just get some Fish glue .It`s very easy and there`s no rush .It reacts exactly like hot hide glue for removal and cleanup .
Did I answer the main question ? No the method applies to any kind of wood .Maple.Also Mahogany ,Rosewood,Etc.
Even when some violin makers only use Fish glue there is a useless tendency to use that dreadful bottled hide stuff . Fish glue is not even expensive .

[MikeCooper]

Sometimes poplar is used for backs, but that's not the usual.

[John Cadd]

I was surprised to see so much Poplar on sale for violins. This was a Bosnian site selling Maple/Poplar wood . I don`t know why it`s got the diagonal mark between them . But very attractive appearance . A one piece back sells for 140 Euros.My laptop does not have a Euro button .
A good cure for a separated back is a one piece back if you want a replacement . Let`s face it --if Spruce trees were as thick as they used to be , some violin makers would be making one piece tops .

[John Cadd]

The brass straps ,in fact, were not used for joining the backs They work well if there is an internal crack away from the edges . But they are too forceful for this .The interlocking wooden pieces were just less than 1/4inch thick.I started fitting them as straight pieces but the internal curve needed to be adjusted gradually as the correct fit was approached.The curve changes all along the internal surface and that is the bones of how this works.Several gentle fittings are needed.Each time the two halves are held together at the C bouts and a thin piece of notepaper cut to make a feeler gaugewhere the interlock pieces touch the opposite halves .A sharp pointed knife is used to alter the fit . You have to put one half down to do that .All the while avoiding scratching the joining surface. Eventually , after checking each side , the arching shape starts to come together . I used an oblong wooden frame to sit the back on . As the back comes into shape the dip ,caused by the interlocks , starts to go in the opposite direction which would show the seam starting to open . The interlocks are working to stabilise the whole effort. The final stage of fitting is to gently squeeze the halves together and use paper tape across the join . So the interlocks are acting as a hinge .The tape closes the tiny gap .
Then separate the two halves .Apply the Standard 24 hour Araldite carefully to both halves.Put them together and make sure the top and bottom edges are in line.The supporting frame is useful get your fingers at the edges.Squeeze the halves together --Gently and apply the cross tapes with enough tension to close the join . The first few tape pieces will buckle up as the others are fitted . They need to be refitted until everything settle evenly without any steps between the edges.Feel across each tape with fingertips to check for smoothness.
12 hours later the Araldite is still soft enough to cut away with a sharp chisel . It will take varnish with it but the wood is safe if you are careful . use the chisel with a sideways slicing action and a gentle contact. Rely on sharpness here . Don`t use a pushing action .
The back wood has a ripply surface and the araldite needs to be cleared out of the dips . Use a bright light to see the reflections.
That all sounds improvised but worked like a dream . The seam joint is really thin .Much of the varnish had been worn away by players over the years .
Incredibly this back is 6.5mm thick at the centre and very gradually tapered to the ends . I wonder what it sounded like . The label was for Del Gesu and below Made in Czechoslovakia.

[John Cadd]

I call the first join a win . The join line is even but if you hold the plate up to a strong light you see light coming through the Araldite in a 2 inch section . That will not come apart .
The second broken plate is more compicated.The original joint broke apart cleanly from the bottom to just near the sound post area.Then the grain line deviates and the split follows the grain about 1/8th inch away from the centre line.So the wood has shrunk away enough to put a table knife through the gap until the top end at the button where the wood comes in contact again . There is damage at the button and traces of tough rubbery glue need to be cleaned away . Maple has a good habit of breaking without tiny or large splinters which spruce would have. I bought some AliExpress bassbars which were mostly exactly straight grained and quarter sawn . But two of them had straight grains along the top edge but 45 degree slants at the ends . They will be cut up for new interlock pieces .The wood will be softer to trim to shape . This time I will space the interlocks apart to use a proper feeler gauge instead of pieces of paper . Both these damaged back plates had suffered damage at the button .Two separate renovation efforts needed there . The second plate with the wayward split has very good thickness dimensions .It should sound good . Ever the optimist .

[John Cadd]

The second back to be repaired is easier than the first . The trick is to make all the interlocking pegs exactly the same.The back of the pegs are glued away from the split .One quarter inch from the end is marked all round with a pencil.That sits on the join line. Just outside that mark a shallow cut is made for adjusting the fit.That cut is on the same surface as the glue .Before the pegs are glued on ,each bottom edge is bevelled to minimise later trimming . When the two halves come together the centre part is more curved and some of that overhang has to be trimmed back.The shallow cut avoids interfering with the join surface.
It`s difficult with two loose pieces to estimate how out of line the edges are.A broken violin may have been left for a number of years in that state .
I think the renovation would be too expensive for a professional repairer to bother with but I don`t regard it as a waste of time .After a little practice each stage does not take very long . Delays while glue is left to dry are quite normal in instrument making and repairs . Long time use showing varnish wear at the chin and shoulder areas tell a story .Somebody must have enjoyed the sounds .
Pictures would be nice but they can disappear after a few months and written descriptions are more permanent .Pictures do not always contain reasons or explanations .

[John Cadd]

The second back is now put together. This time I used the same Araldite glue ,plus paper tape stretched across and then the brass crack clamps . I had not used these brass clamps before .They arrived straight and needed some gentle bending .I put tape where the centre of the brass bar touched the back..There were light cracks without the clamps so it will be more stable . The squeezout can be trimmed away after twelve hours more easily .The edge alignment was accurate because of the shallow cuts on each interlocking peg.It was simple to count along to see those 1/16th inch overlaps in place.
One plastic clamp at each end made sure it would lay flat .
The surface of this maple back is smooth but the first one I repaired had physical ripples . Is there a way to avoid ripples? Does it affect the tone ? Or are ripples an added attraction ?

[John Cadd]

A light teast on the second back ,holding the plate against a stron light shows a thin patch of light near the top end about 2 inches long.That will not be a problem with Araldite,which is a better gap filler than hot Hide Glue. The job needs several actions to be done without delays and hot hide glue would not allow such a luxury. Fitting 5 brass strap clamps alone would make it too slow for Hide Glue. Fish glue could be used with it`s slower open time but that might not be such a good gap filler. There are no actual gaps now but I`m thinking "There might have been".
Now I need to fit two buttons . One was damaged and one is missing . Below a button that breaks is a weakness (cracks or splits) in the top of the back .That repair is called Doubling the Button.
If an Araldite neck join is used the neck breaking would rip a violin to pieces . That repair is done with hot hide glue.---Not cold hide glue.

[John Cadd]

[quote="John Cadd"]A light test on the second back ,holding the plate against a stron light shows a thin patch of light near the top end about 2 inches long.That will not be a problem with Araldite,which is a better gap filler than hot Hide Glue. The job needs several actions to be done without delays and hot hide glue would not allow such a luxury. Fitting 5 brass strap clamps alone would make it too slow for Hide Glue. Fish glue could be used with it`s slower open time but that might not be such a good gap filler. There are no actual gaps now but I`m thinking "There might have been".
Now I need to fit two buttons . One was damaged and one is missing . Below a button that breaks is a weakness (cracks or splits) in the top of the back .That repair is called Doubling the Button.
If an Araldite neck join is used the neck breaking would rip a violin to pieces . That repair is done with hot hide glue.---Not cold hide glue.[/quote]

[John Cadd]

The interlocking way to join violin parts has developed nicely now . The most damaged violin had 2 full length splits ,following the grain. The most delicate part is 3/16th inch wide just passing along the edge of the sound hole top circle . Then there are 2 sections containing the sound itself. The bottom part had a rubbery cold hide glue joint badly fitted and that was separated and joined together to match the arching curve .
Pair that with the opposite side of the top plate.Identical damage still needs to be done properly . The plate thicknessing looks good although the crude carved in bassbar will be replaced .The longest repair needed 20 interlocking pegs. I will leave those in place till the final clean up . This repair has become so reliable I have no nerves about getting it all working again . It will need a soundpost patch .It will be my first one ever .That area was cut too thin but the rest looks good . There is no such thing as standardised thicknessing but it is within Guarneri measurements.
I took all the ribs apart because of lurking nasty glues that don`t belong on a violin . I made a mold to fit proper blocks in the C bouts .
I bought a set of 5 tiny brass crack clamps but they are awkward and heavy for this plate. Using paper tape and wooden pegs seems more reliable .An odd little discovery.

[John Cadd]

The reconstruction of the worst damaged top has been completed. Some joints glued with cold hide glue were taken apart as they disturbed the arching lines .There were a number of hot hide glued joints with too much glue and some dirt mixed in.The longest joints were put together without the ends matching .This was added to by the embedded cleats (grain lines at 90 degrees to the plate lines).All those cleats were removed .
The total number of pieces to reconstruct came to Ten. Now the whole plate is one secure piece .There was one join I was not happy with.It ran from the bass side bottom of the sound hole to the bottom. I taped along the side of the join both sides and also internally. Leaving that overnight with wet tissue taped in place (inside and out) I was able to realign the edges after removing the tissue. It was a simple finger pressure to squeeze the wood in line . That took a few minutes..One other join might get the same treatment .It is the thinnest strip that ran close to the carved in bassbar . Finger tip smoothness is the standard I am using . Any disturbance in the arching sticks out like a sore thumb visually ,much more than I would have expected .A second check is to hold a ruler across the plate under a strong light . The narrow shadow displays the arching line very clearly .
This plate began life with long gouges made by a confident maker ,but the ends of some gouges finished with a break instead of a clean cut .The idea of a smooth surface was unknown to this maker ,whereas the back was as mooth as a baby`s bottom .
Now all the joins have been made with Fish glue I am always able to make final adjustments anywhere necessary . The rickety internal surface was not suitable for a sound post so I smoothed that area and fitted a patch made from a previous violins cutout leftover . That will be 3.5 mm thick .But handling this plate now it sounds very resonant . The slightest rubbing makes a clear rustling sound .
I dispensed with the interlocking pegs for shorter joins . Paper tape was the main help. For these curved piece the first step after lining up the ends is to tape the middle of the curves . Fit the two sections at an angle to start with.Then gently close the angle a bit and tape either side of the first tape . That creates a tension with the gap still open a crack.Now turn the whole thing over .Squeeze glue into the open crack and trail a tin spike along to make sure the glue is right inside. Then start closing the crack and taping the joint closed . Work outwards from the centre.Squeeze the two pieces closed with the left hand while you add tape across the glue line. You may find that tape will not stick to bare wood properly so smear some fish glue on the surface first .That makes it tacky enough .
With all the tape in place you may not have enough ways to double check the final edge positions but that can be refined later .Trust your fingertips at this stage . Well it`s not as hard as brain surgery after all .

[John Cadd]

[quote="John Cadd"]The reconstruction of the worst damaged top has been completed. Some joints glued with cold hide glue were taken apart as they disturbed the arching lines .There were a number of hot hide glued joints with too much glue and some dirt mixed in.The longest joints were put together without the ends matching .This was added to by the embedded cleats (grain lines at 90 degrees to the plate lines).All those cleats were removed .
The total number of pieces to reconstruct came to Ten. Now the whole plate is one secure piece .There was one join I was not happy with.It ran from the bass side bottom of the sound hole to the bottom. I taped along the side of the join both sides and also internally. Leaving that overnight with wet tissue taped in place (inside and out) I was able to realign the edges after removing the tissue. It was a simple finger pressure to squeeze the wood in line . That took a few minutes..One other join might get the same treatment .It is the thinnest strip that ran close to the carved in bassbar . Finger tip smoothness is the standard I am using . Any disturbance in the arching sticks out like a sore thumb visually ,much more than I would have expected .A second check is to hold a ruler across the plate under a strong light . The narrow shadow displays the arching line very clearly .
This plate began life with long gouges made by a confident maker ,but the ends of some gouges finished with a break instead of a clean cut .The idea of a smooth surface was unknown to this maker ,whereas the back was as smooth as a baby`s bottom .
Now all the joins have been made with Fish glue I am always able to make final adjustments anywhere necessary . The rickety internal surface was not suitable for a sound post so I smoothed that area and fitted a patch made from a previous violins cutout leftover . That will be 3.5 mm thick .But handling this plate now it sounds very resonant . The slightest rubbing makes a clear rustling sound .
I dispensed with the interlocking pegs for shorter joins . Paper tape was the main help. For these curved piece the first step after lining up the ends is to tape the middle of the curves . Fit the two sections at an angle to start with.Then gently close the angle a bit and tape either side of the first tape . That creates a tension with the gap still open a crack.Now turn the whole thing over .Squeeze glue into the open crack and trail a thin spike along to make sure the glue is right inside. Then start closing the crack and taping the joint closed . Work outwards from the centre.Squeeze the two pieces closed with the left hand while you add tape across the glue line. You may find that tape will not stick to bare wood properly so smear some fish glue on the surface first .That makes it tacky enough .
With all the tape in place you may not have enough ways to double check the final edge positions but that can be refined later .Trust your fingertips at this stage . Well it`s not as hard as brain surgery after all .[/quote]

[John Cadd]

One of the features of the most damaged violin I am renovating is that each "component" has been separated and the edges have been cleaned . The reconstruction has had every joint fully glued together as if it was the centre joint .Normally centre joints are not reinforced with cleats . I fitted some cleats where one end arrived at the soundhole. Where sections had both ends arriving at the outer rim they were left without cleats .
The question in my mind is about many cleat repairs shown on youtube . Are those splits and cracks only partially glued together after the repair ? Easing a crack open to work glue in with a fingertip might be the best the repairer could manage . There is a trace of uncertainty especially if the top is left attached . That`s a perspective question more than any sort of criticism .
This repair did not involve any actual breaks in the wood .They all followed grain lines . Also simplifying the job is that humidity changes were not involved .
The original maker cut the bassbar in situ .Fitting the proper bassbar It skated very close to the top soundhole edge . I cut a tiny bit out of the bottom edge . That`s another first apart from the soundpost patch . I had to fill in the numerous shallow graves cut out to hold previous cleats that had mostly fallen out by themselves . Many cutouts show the misalignment from the ends being left out of line . That`s the beauty of no purfling .You could get away with it . I made a mold to allow 4 blocks to live inside . Then I will build up some broken away edges in the bouts . The final touch will be to add purfling using my new cutter attached to a Dremel . The thread size was all wrong and I had to improvise by tapping the plastic into the alloy . Some good basic engineering there . But it`s very secure . The Dremel will be my dedicated purfling tool from now on . It will be my all singing all dancing violin .
The prospect of this repair was a bit daunting but it`s making me very happy .