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I’ve sprayed nitro lacquer on about 60 instruments and have never seen this before.
Behlen instrument lacquer over Zpoxy.
Mahogany neck, Cebil fretboard.
I’ll sand it down and reshoot.
The other side of the board looks fine.
I suspect water somehow wicked in during wet sanding.

Does anyone have a clue as to why this happened?

Can I just sand the affected area and reshoot lacquer including the polished surfaces?

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Not sure what caused the peeling, maybe water, but you need to sand the glossy parts in order for the nitro to stick there.

Best to scuff the shine off before spraying.

Cal

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Remember, there are no stupid questions, only stupid answers!

I started scraping the affected area and found out the lacquer on the entire neck can be peeled off.
I’m using a razor blade with a burnished edge.
Not sure how I will remove the lacquer. I may try thinner or acetone.
Hopefully the color under the Zpoxy will not get buggered up.
I have no issues with the body, I sprayed the body and neck separately.

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Water would not cause this. You might have a contaminate like wax or silicone that prevented burn in between layers.

If removed lacquer off necks with lacquer thinner. Wipes right off.

I scraped the lacquer off and cleaned up with lacquer thinner.
There was a two month period from first to last lacquer applications.
Maybe I should have thinned the lacquer when I started the delayed second application to allow it to burn in?

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I'm an amateur at finishing. What I'm reading about is a neck that got contaminated with something between finishing sessions. Was there any activity in the building that would have created a cloud of wax/silicone/cooking grease/cooking oil that might have made its way to the neck? Clouds can be awfully diluted and still cause trouble.

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Peter Havriluk

I blew off the dust and cleaned with Naptha prior to spraying.
The neck was hanging in my shop, I can’t imagine it got contaminated.
Good point, and possible.

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Any chance that the cloth used in wiping down with naphtha was contaminated with something, something from the household and not from new cleaning cloth?

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Peter Havriluk

No, I use Kimberly Clark paper towels that I store in a closed plastic container.
I’m careful about keeping these perfectly clean. I never reuse one.

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I worked at Intl. Luthier Supplies back in the '70s and we had a customer that had varnish peeling off his newly built violin. It took some inquiry but we finally realized he was using a "furniture polishing cloth" as a tack rag that he had purchased for this purpose. Problem was that the cloth was saturated with silicone. Not saying this is your issue, but that it can be unexpected where contaminants can show up. For example, some sandpaper has stearate which creates similar problems.

I sanded the neck to bare wood, added color, and sprayed two coats of thinned lacquer.
i noticed the lacquer in the can was cloudy and sprayed anyways (what a dummy).
I added thinner and stirred it but still cloudy.
Maybe the lacquer was bad when I first sprayed the neck and caused the failure.
I bought it this year, no extreme heat or cold.
I guess I’ll sand the existing lacquer and hope I don’t muck the color (dye).
Does lacquer go bad?

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I have had 10 year old lacquer that still worked fine. However, it was stored in a glass jar. But one year old lacquer is not the problem. May have just been a bad mix.

Thanks,
I sent a query to Mohawk with the lot number.

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The cloudy stuff suggests some ingredient that shouldn't be there.

I think it can go bad. I had some lacquer that turned real dark while stored. Way off color. I threw it out.

Real nitro is organic, so I guess anything could happen.

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"Act your age, not your shoe size" - Prince

It's not like food. There is no bacteria that could ever live in lacquer. The only possibility I see is some type of chemical reaction. But I think it is much more likely that someone did an improper mix. Whatever it is, I would throw it out.

I spoke with the Mohawk dude.
He said if it’s cloudy, it’s contaminated and not to use it.

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how find did you sand? past 220 and you loose tooth
a did you seal the wood before spray and what sealer did you use
what stain did you use and what filler

I have had this happen one time using vinyl sealer . thought 4 coats would be good
nope sealer 1 coat is all you need. Also did you thin?

finish work is about as much on technique as it is what you spray.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks John,
I applied alcohol based dye to bare wood, Zpoxy grain fill, sanded to 220.
No sealer. I shot Behlen nitro full strength, thick coats.

Repair:
I sanded everything back to bare wood. Applied dye and Zpoxy.
I thinned the (new can) lacquer and built up thin wet coats.
So far, it looks fine and I don’t see any evidence of peeling.

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I’ve had this happen before. Usually it happens on a instrument in for repair and never when I’m building as I use automotive product or water base for the most part. With nitro tho,What I always do is add lacquer retarder to the clear coat. It allows the nitro more time to melt into the previous layer/layers. It won’t help with spraying directly to zpoxy as that is a mechanical bond, but it will help nitro melt into the previous layer.


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