Finish Crack Touch Up

[Philip Secrist]

I have performed many finish touch ups with great success, but this one makes me a little nervous. I have a Martin OM-28 on my bench with a simple top crack. It was a very tight crack. It actually did not crack all the way through the top.  The crack has been repaired successfully by working in some glue and clamping it up. The crack closed up nicely but the finish crack is still visible and the unevenness can be felt when running the fingertips over it (the crack is visible in the reflected light area in the finish crack pic attached).  The customer would like to sell it so he would like it to be as close to new as possible.  The guitar is about 7 years old so the nitro finish has sunk into the top grain just slightly enough that you can feel a subtle ripple on most of the top surface. My concern is if I fill the crack with a tiny bead of lacquer, let it cure, level it and then buff it out, will the repair area stand out too much from the surrounding finish area. My plan, of course, would be to keep all leveling and buffing restricted to a very narrow area on either side of the crack as much as possible.  Those of you who have done a lot of finish repair work, is it better to have a small smooth area around the crack compared to the slightly rippled finish on the other areas of the top, or to leave a visible finish crack that can be felt?  Is there a compromise or a method that I am not aware of to blend this in and with the most success?

[Eric Steven Johansen]

Philip, For tight cracks such as this I use a tiny brush and run a bead of lacquer retarder into the crack and let it melt the finish back together. I go back an hour later and if needed repeat the process. I let it dry for a few days and hand buff with a fine compound.

[Philip Secrist]

HI Eric,  I am not sure I can get any retarder into the crack since it has been glued. Will the retarder help to even it out. It almost feels like a slight depression where the crack was (very subtle).

[Eric Steven Johansen]

The retarder will penetrate into the lacquer, crack or not, and should make the crack disappear. As for the indentation you could mix a little lacquer with the retarder to create some build.