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PostPosted: Tue Nov 08, 2022 11:45 am 
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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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PostPosted: Tue Nov 08, 2022 2:00 pm 
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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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These users thanked the author Cal Maier for the post: dzsmith (Tue Nov 08, 2022 2:05 pm)
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PostPosted: Tue Nov 08, 2022 2:38 pm 
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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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PostPosted: Tue Nov 08, 2022 3:59 pm 
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Water would not cause this. You might have a contaminate like wax or silicone that prevented burn in between layers.



These users thanked the author Barry Daniels for the post: dzsmith (Tue Nov 08, 2022 5:17 pm)
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PostPosted: Tue Nov 08, 2022 6:41 pm 
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If removed lacquer off necks with lacquer thinner. Wipes right off.



These users thanked the author Glen H for the post: dzsmith (Tue Nov 08, 2022 8:16 pm)
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PostPosted: Fri Nov 18, 2022 6:19 pm 
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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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PostPosted: Tue Nov 22, 2022 7:33 pm 
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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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PostPosted: Wed Nov 23, 2022 10:22 am 
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phavriluk wrote:
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.


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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PostPosted: Wed Nov 23, 2022 8:23 pm 
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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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PostPosted: Wed Nov 23, 2022 9:28 pm 
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phavriluk wrote:
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?


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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PostPosted: Thu Nov 24, 2022 11:11 am 
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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.



These users thanked the author Barry Daniels for the post: dzsmith (Thu Nov 24, 2022 12:35 pm)
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PostPosted: Tue Dec 06, 2022 4:26 pm 
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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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PostPosted: Tue Dec 06, 2022 6:41 pm 
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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.


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PostPosted: Tue Dec 06, 2022 7:05 pm 
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Barry Daniels wrote:
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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PostPosted: Tue Dec 06, 2022 7:17 pm 
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The cloudy stuff suggests some ingredient that shouldn't be there.


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PostPosted: Tue Dec 06, 2022 7:32 pm 
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I think it can go bad. I had some lacquer that turned real dark while stored. Way off color. I threw it out.


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PostPosted: Tue Dec 06, 2022 7:39 pm 
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Real nitro is organic, so I guess anything could happen.

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PostPosted: Wed Dec 07, 2022 9:03 am 
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Brazilian Rosewood
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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.



These users thanked the author Barry Daniels for the post: dzsmith (Wed Dec 07, 2022 9:25 am)
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PostPosted: Wed Dec 07, 2022 11:58 am 
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Barry Daniels wrote:
The cloudy stuff suggests some ingredient that shouldn't be there.


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

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