People oftentimes call about a crack in the face of their acoustic guitar, ( or the side or the back) and need to know how this will affect the sound. Does this make the guitar more fragile? Will the crack spread? How does one fix this problem????
I’ve heard several people tell me that if you just squeeze the cracked area, one could actually close the crack; but 99% of the time these cracks are caused by shrinkage or banging the guitar against something hard, and actually breaking the wood. No matter how much clamping you do all you will likely do is make things worse.
The real answer is to carefully reinforce the back side of the crack (depending on how long the crack is, and where it is) with what is commonly known as a “cleat of similar wood”. What this will do is to actually join the cracked area, making it stronger than before, and squeezing glue up thru the cracked area. This must be done is a most careful manner.
The photos show an invention I devised to pull a small cleat of spruce, rosewood, or mahogany thru the sound hole, and carefully, but firmly, increase pressure on the back of the cleat, and at the same time flatten out the area where the crack may be “feelable”.
In other words, the guitar area isn’t perfectly flat and needs to be. This will also dramatically eliminate the crack from spreading up or down or in any direction. If a crack is several inches long, then several cleats may be necessary to reinforce the damaged area and add to the stability of the crack.
The photos show the tools I’ve invented, and what the cleat looks like from behind on a 1930 Gibson guitar. If you’re getting this far into repairing guitars I invite you to examine the repair, and do your own brain work; figure out how I make this work. I can’t give away all my secrets, but with a little brain power and some experimentation, you’ll get it.