BEST way to repair Nitro finish?

[John Meyers]

I was installing a pre-amp into a bass I built and when drilling the hole for a selector switch, the bit chipped the finish. So I took some CA to drop around the chip. When I did this there must have been an air bubble in the bottle of CA and it shot some onto another part of the body and when I noticed it I whiped it off, only to find 3 indentions in the finish. It looks like it melted the finish where the drops landed. What will be the best route to fix, with out having to break the bass down and re-finish the body again.

1- Could I take something small and drop fill the indentions with nitro, or will this leave a noticble mark agter sanding and buffing?

2- add more CA to those drops and sand and buff?

Let me know what you think?

[Rodger Knox]

Either way should work equally well. If it ever happens again, don't wipe it off! It's relatively easy to scrape off the little bumps of CA, much easier than filling low spots. You usually end up needing to scrape after drop fills anyway, so not wiping saves you a step. DAMHIKT

[Michael Lewis]

On nitro lacquer I will give opposite advice: WIPE IT OFF IMMEDIATELY OR IT WILL EFFECT THE LACQUER. It's probably OK to smear the CA very thin so it "dries" very quickly and doesn't have time to soak into the finish. It can be wet sanded and buffed out because it's on the very surface, but if the CA stays on the lacquer it can effect it clear through to the wood. It is easier to clean up and buff a thin smear of CA but not so easy to make drop fills totally match the original finish. Drop fills will take a while to gas out all the thinner and will show uneven surfaces a while after it has been leveled and buffed as it continues to shrink.

When I spill CA I wipe it up immediately and deal with the aftermath, but drop fills can take weeks and months to "get it right".

[John Meyers]

Either way should work equally well. If it ever happens again, don't wipe it off! It's relatively easy to scrape off the little bumps of CA, much easier than filling low spots. You usually end up needing to scrape after drop fills anyway, so not wiping saves you a step. DAMHIKT

On nitro lacquer I will give opposite advice: WIPE IT OFF IMMEDIATELY OR IT WILL EFFECT THE LACQUER. It's probably OK to smear the CA very thin so it "dries" very quickly and doesn't have time to soak into the finish. It can be wet sanded and buffed out because it's on the very surface, but if the CA stays on the lacquer it can effect it clear through to the wood. It is easier to clean up and buff a thin smear of CA but not so easy to make drop fills totally match the original finish. Drop fills will take a while to gas out all the thinner and will show uneven surfaces a while after it has been leveled and buffed as it continues to shrink.

When I spill CA I wipe it up immediately and deal with the aftermath, but drop fills can take weeks and months to "get it right".

Thank you both. It did leave indentions in the finish after I wiped it off and it does look like they go deep into the finish. I went ahead and sanded back around the indentions just to thin it out some and dropped some Nitro back in and I will see how it goes.

Let me ask this as well. How well does Nitro burn into its self? Reason I ask, once I get the drop fill comeplete and sanded could I spot spray the area and buff out and it not show any evidents of anything being done? Or should I just sand and buff the area and let it be?

[Rodger Knox]

I guess I should have been a little clearer with my recommendations! I was talking about TINY droplets, not large enough to eat through the finish. Sometimes a CA bottle will "spit" when an air bubble pops or something, and the tiny droplets go everywhere. In 10 seconds, they'll be dry enough to scrape off with a razor blade. If you wipe it, very little actually come off, it just gets spread around. If the drop(s) is/are larger than that, the torn corner of a tissue is very effective in sucking up excess CA. When I said don't wipe it, I meant don't expand the extents of the damage.

edit:You posted while I was typing. I don't spray lacquer, so I don't know for sure, but like many things in luthiery, it will probably work as well as you make it work.

[Barry Daniels]

Nitro burns in well.

[Michael Lewis]

It depends how thick the finish is. The thicker it is the longer it takes to shrink. Could take several weeks to approximate 'stable'. You can level and buff lacquer after a couple days and make it look perfect but in a week or so it will shrink and you will see the "repair". It takes weeks for the finish to settle in and stabilize.

[Michael Polutta]

FYI - Get the 'whip tips' (available at StewMac) to avoid that kind of CA splash out of the tip on the bottle.

[Michael Lewis]

Better yet, don't try to repair nitro lacquer with CA. CA is harder than the lacquer and will sand at a different rate, and will buff to a different gloss, often more glossy than the surrounding lacquer.

[David King]

I never pickup the CA bottle without picking up a paper towel in the other hand. I do have to remind myself of this rule every time but after making this mistake many dozens of times I have no trouble remembering now.

[John Meyers]

Just to give an update. The repair came out great and you cannot tell it ever happened. I just dropped filled the spot with a Q-tip a few times and let sit for a week sanded back. I had just a little spot left, so I added more Nitro to it and let it sit for another week. Sanded and buffed out to a perfect shine. I do not care for Nitro for all of it's drawbacks but when something happens it is easy to repair which is nice.

Thanks everyone for your help.