Heat Failure
Backstrap Overlay
© Frank Ford, 7/2/02; Photos by FF

This mandolin had suffered a bad blow, breaking the peghead along the grain right behind the nut. The good news is that it was repaired using the backstrap overlay technique. The bad news is that the repairer used Titebond aliphatic resin glue, which is not heat resistant. So, with the high heat of a parked car, the glue simply liquefied, and the original damage was revisited:

Here, you can even see the strings of melted glue which had become about as strong a chewing gum in the heat, and then become solid again when the temperature dropped:

Ordinarily, I'd want to use traditional hide glue on this kind of break, but here the amount of contamination from previous glue would have prevented good adhesion. So, in spite of the fact that it can attack the finish, I chose cyanoacrylate, first running in a bit of the thin stuff to wick way up into the crack, and then following with the thicker gap-filling variety:

Both hide glue and cyanoacrylate are extremely heat resistant in the range encountered in parked cars.

No problem getting good clamping pressure with a solid flat caul on the face of the peghead and a thick shoe leather resilient caul on the back of the break:

The cyanoacrylate squeeze-out also served to fill the finish in the area of the break:

I sanded the finish level with some 600 grit no-load aluminum oxide paper wrapped over a cork block:

A quick introduction to Baldor the Magnificent, and the repair was polished nicely:

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