Guitar Scratch Repair - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien showcases a practical demonstration of repairing finish scratches on a guitar, offering clear guidance and techniques to restore the instrument's aesthetic appeal.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: I scratched the top of my guitar with a fingernail while French polishing. Is there a way to fix this?
Robert O'Brien: Today's Tips du Jour mailbag question comes to us from California. "Robert, I was French polishing my, I mean, my friend was French polishing his guitar when he caught an edge during the spiriting off stage and left a fingernail mark in the top. Is there a way to fix this, Eric in California?"
Eric, I feel your pain. In fact, this happened to me just a couple of days ago. Ideally, you should wear a glove or trim your fingernails on the polishing hand, and hopefully that will keep you from leaving a mark on it. When it does happen, there is a way to fix it. Let's step over to the bench and I'll see if I can show you how.
How to fix fix small dents and scratches in guitar tops
Eric, here's the mark in my guitar. I don't know if you can see it very well in the camera, but I can certainly see it here in the shop, and I know that the person that gets this guitar is going to see it.
I was spiriting off just like you and I caught the edge here and my fingernail damaged the top. If you're going to have a scratch in the top of your guitar, this is one of the better ones to have. It goes with the grain, and those are a little easier to hide than the ones that go diagonal or across the grain.
Here's a little different camera angle. Perhaps you can see that scratch now. There it is, and wow, does it really show up? I've got to do something about that. The first thing you'll probably want to do is just sand it all the way back to bare wood in that area. Don't do that. Resist that temptation because if you do, you're going to have a little lighter colored area there. You'll have a blotchy area and it's going to show up even worse.
Clean the area with Naphtha
Right now, leave the finish on, don't take it back. The first thing I'm going to do is put a little bit of naphtha on a rag and just clean the area. The reason why I'm going to do that is I want to get rid of any oil perhaps that was there during the French polishing sessions, so that what I'm going to do next will stick to it. Go ahead and just clean the area there with some naphtha. By the way, what I'm going to show you here, this technique also works well for other types of finishes like lacquers and urethanes and polyesters. I just happen to be doing this on a shellac finish. I've placed a piece of paper on the surface here to protect this area out here. Just take a piece of paper, tear a hole in it [Robert covered the entire area surrounding the scratch and placed the hole over the scratch area].
Level the scratch with thin viscosity CA glue
Now I'm going to place just a little bit of thin viscosity CA glue into this yogurt top here. Now I'm going to take a needle and pick up just a small amount of that thin viscosity CA glue and just place it down inside the scratch.
What that's going to do is help level the scratch. Now you know why I have this piece of paper over here, because if I drop a small amount of CA glue onto the other part of the top, I don't want to do that. Okay. The next thing to do is just to let that dry. Whatever you do, don't use accelerator on it. Just let it dry. It'll take a few minutes. If you use accelerator, you're going to get small air bubbles in there, and it's going to turn white in some areas, so just let it dry, walk away from it. I'm now going to take a small razor blade and wrap a piece of clear tape on the corners like this. And then as well on the other corner. That leaves an open part in the middle. And if I place that over something, I've got a little open space in there that is exactly the thickness of my tape. I'm going to place that over the CA glue where I did the patch and scrape that CA glue down flush with the top.
And you want to work very slowly, very carefully here. The idea is to scrape it down flush, so the only CA glue on there now is in the scratch or in the low area. If you think you need to, you can hit it with a very high grit. This is a 1000 grit dry if you want to hit it just very lightly. Now I have the scratch level, and it's almost invisible to the eye now because it's level.
Refinish the repaired area
Now I'm going to come in and French polish right over the top of that. Now, if this were a lacquer or a polyester or a urethane type finish, sometimes that alone is enough to fix the scratch or the dent. All you need to do now is just wet sand and get it back to a high gloss. Since this is a French polish, I'm going to French polish right over the top of it, and it will become invisible at that point. Notice this time though, Eric, that I've learned my lesson and I'm using gloves. Hopefully that will keep me from scratching the guitar again as I'm completing the French polish. Eric in California, I hope you found this information useful. And by the way, this tip also works well for removing small dents and fingernail marks from the tops of your guitars. Happy building.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
