As shown in the photos above, we have an example of a crack that runs about 2 inches above the left f-hole of a viola.
There are two ways to go about this: The proper way would be to remove the entire top by separating it from its ribs, apply animal glue to the crack joint, and secure the crack further from opening in the future by means of studs or cleats beneath the crack.
The second way, which we will explore in this article, is a quick fix. I chose the quick fix for a number of reasons:
- at 2 inches, the crack is a rather short one, and should remain quite stable after repair, with good reinforcement from the wood surrounding this area.
- the crack exists in a region with little or no pressure or force, except for a foreseeable slight downward pressure and bending moment from the bridge, which by nature would already have dissipated slightly from the discontinuity provided by the f-hole, as a finite element analysis would suggest.
- taking an entire top off and having to reassemble the pieces together, including readjusting bridge and soundest position didn’t seem at all like a worthwhile effort for a relatively short crack on a viola that didn’t bear the name Stainer, Stradivari or any other big German or Italian name.
Violin Top Crack Repair
For a job like this, super-glue would work best because one, this is a crack that we do not expect a need to open in the future, and two, super-glue is strong and rather stable with temperature and humidity fluctuations.
However, super-glue could potentially damage the pristine varnish of the viola as avoiding getting the glue on the surface around the crack would be quite impossible.
Also, unwanted super-glue is quite hard to remove without leaving a stain, and commercial super-glue removers would be detrimental to the varnish.
There is certainly a risk working with super-glue in this instance, not one I was about to take for this viola.
Instead, I decided to go with convention and used animal glue instead.
Boil and prepare only a small amount, and use a flat tip art brush to work the animal glue into the crevice. Although the glue is fluid enough to flow into the crack, you may want to use a feeler gauge to pry open the crack slightly to ensure the crack surface area has been optimally applied with glue.
Be careful not to pry open too wide and extend the crack longer than it already is!
Close the crack up by lining both sides of the crack to the same level. You may want to further brush a moderate amount of glue on top of the crack line and gently tap it into the crack with your middle or forefinger.
In our example here, it was necessary for me to introduce a block and cork to keep the top surface and both sides of the crack at the same level, aided by the downward pressure from the C-string.
Any unwanted glue on the surface should be removed by wiping down with a soft cloth slightly damp with warm water. A warm wet cloth will remove animal glue quite easily as animal glue workability is dependent on temperature.
An F-clamp was used to maintain lateral pressure to keep the crack joint sealed and in contact while the glue cured. The viola was then put aside for a minimum of 12 hours before the tools were removed and returned to the client.
I apologise for the lack of photos for this article, as I had decided to write this after the job was done, not thinking that I’d need to document its process.
See the links below for animal hide glue for your woodwork.