Of all the guitar repair jobs, finish touch-ups or repairs are probably the trickiest. And unfortunately I have a couple on the Guild F50.
These are some nicks on the top of the guitar. I'm going to touch them up with some closely matched lacquer, top them with clear to level and hopefully they'll look less obvious.
Older guitars were finished in nitrocellulose lacquer, aka 'nitro.' Not to be confused with nitroglycerin, or the nitromethane that dragsters run on.
This stuff is really great to use, mainly since it will 'melt' into previous coats. So for touchups, you won't have obvious seams as you would with a poly finish. Plus it sands and polishes like a dream.
Whenever I think of nitro, I recall those old spy movies where the bad guy had a jar of 'nitro' and threatened to throw it at someone or something, and there would be a big explosion. Nitroglycerine explodes with physical shock. Alfred Nobel, who worked with it a lot, eventually developed dynamite (with nitroglycerine as an ingredient) due to the fact that nitroglycerine was so difficult to handle.
Anyway, nitrocellulose is pretty nasty smelling stuff - you have to wear a mask. There are lots of pictures of folks in the Old Days at Fender and other guitar shops where they sprayed it and didn't use masks. Argh.
Sherwin-Williams makes a LOVOC nitro now that is gaining popularity. I need to check it out.
I tested it right on the spruce patches I just put on. They'll get leveled anyway, so it was the perfect place to try and match the existing color.
I really 'drop' it more than paint it.
Where did you go?
If you look at the larger image, you'll see where the chipped surface is still below the original finish. That's ok. I'll use clear lacquer to build up the height and then scrape and sand it level.
The color's a pretty close match, huh?
This was a big Lesson Learned. I got lazy and sloppy with my heat gun and the finish got blistered here. I'm usually very careful, but this time I goofed.
However, I think I can make it look ok.
See the 'test' spots of lacquer toner on the spruce patch? That's where I tried different colors as I mixed the lacquer - a Vintage Amber base and then a drop or two of the colors I mentioned above until I got it close.
Wet sanded the blisters with 180, then 220 grit paper on a small block. Very gently, not a lot of pressure.
Most of the original finish stayed in place. Very good indeed.
A couple spots went down to bare spruce, but there's still a thin layer of clear lacquer on most of the area.
If all goes right, it will be a decent repair. I think it should be visible only close up and from certain angles, which is pretty much the best we can hope for.