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finish 'blooms'
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=54238		 Page 1 of 1
Author:  flemsmith [ Tue Jul 06, 2021 3:43 pm ]
Post subject:  finish 'blooms'
pix shows recent nitro delam/blooms?! on my first guitar after almost two years of playing. Original spraying was done in summer in Az, where a number of y'all told me about using a retarder when it's very hot. Right now we're in our 'monsoon' season, where there's only periodic rains, but daily cloud buildup and fairly sustained higher than normal humidity. Current humidity is close to 50%, where most of the year even with a humidifier, I can barely keep things as high as 25%. I have no real intentions of selling any guitars, rather just want to make some that can be dependable here in the desert for friends and family, so this issue is unsettling. It has not happened anywhere else on the guitar (yet), and only in the last week or so has shown the failure the picture tries to capture.

Image

So I have two more in works, one with nitro applied, and one which is just getting the binding attached. I'd like to learn how to head off this problem, but I don't really know what to do different in the future. Appreciate any advice/inputs. Thanks, Roy
Author:  Trevor Gore [ Tue Jul 06, 2021 5:01 pm ]
Post subject:  Re: finish 'blooms'
What type of glue? What type of grain fill?
Author:  Jim Watts [ Tue Jul 06, 2021 5:06 pm ]
Post subject:  Re: finish 'blooms'
This almost looks to me like an issue that can happen with aliphatic resin glues such as titebond. Over time the glue can swell and create a bump in the seam, it'll show up in a similar fashion. Although I've not see it quite that bad, so this may be something different.
I'm not sure if it's excess glue that causes it or not.
Author:  SnowManSnow [ Tue Jul 06, 2021 6:02 pm ]
Post subject:  Re: finish 'blooms'
I think it’s the glue… it’s in all the places glue would go:)


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Author:  flemsmith [ Tue Jul 06, 2021 8:12 pm ]
Post subject:  Re: finish 'blooms'
Z-Poxy fill. I'm trying to remember if I didn't use titebond rather than CA for the attachment. Seems like I did, thinking the large wedge area might need titebond, and it would just be easy to put the purfling in with that as well. So, I'm assuming I can do nothing to the second which just might have the same problem, again don't remember for sure, but feels like glue rather than CA too....On the third, I've added the wedge and purfling, but no lacquer yet. Assuming I've probably been consistent, what should I do with the 3rd before I start spraying, which will probably be a couple few months....shellac? Thanks for the feedback, I hadn't thought of that. Roy
Author:  Trevor Gore [ Wed Jul 07, 2021 6:19 pm ]
Post subject:  Re: finish 'blooms'
It's likely residual glue if you used Titebond, a problem called the "Titebond time bomb" in these parts. All surface traces need to be removed or you get what you see. A thick glue line can eventually show up like that, too. I don't know if it's a reaction with the epoxy that causes it or just a "feature" of Titebond. Unless you use a non-bloom type of epoxy, epoxy can go milky without any potential reaction with glue. I understand that some (at least) of the Z-poxy products have the potential to bloom down the track. At least one epoxy that doesn't is the WEST 105/207 combination.

Given that some manufacturers put a fluorescent dye in their glues to make any residual easier to find (under "black" UV light), that would suggest that this type of thing is a known problem of the glue rather than anything else. I don't think it's anything to do with nitro.
Author:  SnowManSnow [ Wed Jul 07, 2021 6:50 pm ]
Post subject:  Re: finish 'blooms'
flemsmith wrote:
Z-Poxy fill. I'm trying to remember if I didn't use titebond rather than CA for the attachment. Seems like I did, thinking the large wedge area might need titebond, and it would just be easy to put the purfling in with that as well. So, I'm assuming I can do nothing to the second which just might have the same problem, again don't remember for sure, but feels like glue rather than CA too....On the third, I've added the wedge and purfling, but no lacquer yet. Assuming I've probably been consistent, what should I do with the 3rd before I start spraying, which will probably be a couple few months....shellac? Thanks for the feedback, I hadn't thought of that. Roy

I’d use a scraper to clean all my he sides and glue lines to make sure nothing has been smeared about. You should be able to feel it pretty easily w a scraper.


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Author:  flemsmith [ Sat Oct 02, 2021 10:08 pm ]
Post subject:  Re: finish 'blooms'
Having just finished my second guitar, I think I'd like to try to fix this issue on the first before going forward on #3, which is awaiting purfling anyway. I'll try to remember to post an updated pix tomorrow when there's decent light. It continues to get worse, delamming the nitro pretty sginificantly, and only in this spot.

So I understand I'll need to take it back to bare wood (which freaks me out a bit), wondering if I can just mask that area off and start with some chemical strip that wouldn't be too harsh to the wood, then I don't really know what a decent process would be to move forward.

Learning new things so I can forget em next week.... Roy
Author:  Clay S. [ Sun Oct 03, 2021 6:43 am ]
Post subject:  Re: finish 'blooms'
If the finish is nitrocellulose the best stripper is lacquer thinner. Strip the finish and then wipe it down with more lacquer thinner and let it dry.
Other strippers often leave behind a residue that must be neutralized or washed off that creates more work than using thinner. nitro is easy to remove.
If you are removing epoxy you may need to scrape or sand it off - not many retail type strippers work on it and industrial strippers are pretty harsh (if you can find them).
Author:  flemsmith [ Sun Oct 03, 2021 10:31 am ]
Post subject:  Re: finish 'blooms'
OK, thanks. It is Nitro, so the stripping seem straightforward. What I'm wondering about is how best to blend the respray to the edge of the existing nitro once I've masked and stripped it so it isn't obvious. Should I spray coats with the masking still on, then remove the tape (or mebbe just move it back from the new/old interface an inch or so) and spray both til I can detect no depression, and then a typical cure, wet sand , etc?

This pix doesn't really add anything, except that it has continued to delam the nitro.

Image

Roy
Author:  johnparchem [ Sun Oct 03, 2021 1:04 pm ]
Post subject:  Re: finish 'blooms'
As suggested this looks like glue as that is where glue would be. On amazon I bought a cat pea black light flash light. With it you can see glue on the surface even if it does not have a florescent dye. Also use soap and water to clean zpoxy due to Amine Blush, it can also be the cause of delaminations (but not so focused on joints.)
Author:  Clay S. [ Sun Oct 03, 2021 6:09 pm ]
Post subject:  Re: finish 'blooms'
If you are only going to do a partial finish removal, you may want to just sand off the finish in those areas, feathering the edges into the remaining finish. I would not mask off, but again, feather the new finish into the old finish to avoid having a "step" in the finish. Nitro is fairly forgiving, so masking and spraying could work, it just may be a little more difficult to blend the new into the old.
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