As a Cleveland-based luthier doing guitar repair and restoration, I see quite a few instruments requiring crack repair. Instruments are allowed to dry out in the winter months or left in cars during the summer. Car interiors can get to over 115 degrees and down to 14% humidity during the summer months! This Harmony Monterey was an extreme case. Five long cracks that all needed to be knitted back together. Here’s a short video on how the repair was completed.