Fixed Crack in Back

[Diane Kauffmds]

I'm obsessive about the care of my guitars. WV has surprisingly low humidity. Even with whole house humidification that runs with our furnace, we struggle to keep the house above 30%, so all of my guitars are kept in their cases with humidity. Unfortunately, I didn't realize it until too late, that the case holding my beloved Alvarez Masterworks MD95, was sitting over a vent. The guitar developed an 8 inch crack along the grain line in the Indian rosewood back. I emailed St. Louis Music and was told that this model was finished with polyurethane.

The crack was just to the left of the center back, under the center brace, so it was stable. I used thin CA glue to further stabilize the crack and I put light counter-pressure on the higher side so that both sides were even. I used a razor blade to even out the glue, then sanded the entire back of the guitar; I was careful not to go down into the wood, but I removed a good 90% of the finish. All of the sanding was done by hand, using 400 grit and a small block of wood.

I used hand applied polyurethane and applied 6 very light coats, sanding lightly between each. After the 6th coat, I polished the back with glass stove-top polish, to make sure that it was very smooth (I'm waiting for a luthier to have heart failure about now!). I put a final 7th coat on the guitar to give it this high polish.

The original finish on the guitar is high polish, so this is what I had to match. I must have done it properly, because she's singing very sweetly with a long sustain and beautiful tone.

Here are photos of the repair:

This is the 8 inch crack:



This is the back after my repair:



This is the high polish original finish I had to match:

[johnnparchem]

It looks great. It appears that the stove top polish works. A lot of us use plastic polish like Novus (2 or 3) or Meguiar's polishing compounds to get a glossy finish after sanding. The stove top polish that I used on my stove was not that different.

[Diane Kauffmds]

It looks great. It appears that the stove top polish works. A lot of us use plastic polish like Novus (2 or 3) or Meguiar's polishing compounds to get a glossy finish after sanding. The stove top polish that I used on my stove was not that different.

Thank you. I'm going to make a note of these compounds. Quite frankly, I had no idea what to use. I figured the ceran cooktop polish was gentle enough for glass, so it may work for poly.