| Official Luthiers Forum! http://luthiersforum.com/forum/ |
|
| finish blush http://luthiersforum.com/forum/viewtopic.php?f=10101&t=55705 |
Page 2 of 2 |
| Author: | flemsmith [ Sun Jun 11, 2023 12:38 am ] |
| Post subject: | Re: finish blush |
Wow, thanks for that. I was thinking to just omit the vinyl seal spray. Did your adhesion issues show up fairly quickly? And were they only related to glue joints as mine seem to be? I'm gonna spend a fair bit of time trying to seal every glue joint I can find before I start spraying. Appreciate the new info. Roy |
|
| Author: | Woodie G [ Sun Jun 11, 2023 7:38 am ] |
| Post subject: | Re: finish blush |
Mr. Smith: I apologize for not having seen this thread earlier. Your issue is not blush or Titebond removal, but rather a compatibility issue between your Z-Poxy filler and player body chemistry. The usual fix is to move to a blush and bloom-free epoxy filler (SilverTip or similar) and better preparation. For existing instruments with finish separations evident, a refinish with a SilverTip fill and lacquer finish on the contact areas of the instrument (usually the neck, but sometimes the body contact areas). Here's what is happening: - The cured Z-Poxy - specifically the excess amine salts which remain on the surface even after diligent soap-and-water rinse and sanding - are reacting to player perspiration which passes through the lacquer finish - This reaction depends on the pH of the player's perspiration... while females tend toward neutral pH, males may be overwhelmingly acidic (down to the mid-5's!!!), which - when reacted with the salts present on the surface of the Z-Poxy fill - will generate both gases and reaction products which compromise the bond between the filler and sealer/finish coats We saw this issue years ago on early Z-Poxy filled guitars, and usually with owners that experienced finish issues on their other, non-Greenridge instruments. After some pH testing, we found reasonable correlation between lower (more acidic) pH body chemistry and failing lacquer. Those instruments were refinished under warranty with SilverTip filler and McFadden or Mohawk standard VOC vinyl sealer and instrument lacquer. None have shown any further inclination towards finish separation. I will also note that we saw separation on some custom-built instruments where we knew the builder was using Z-Poxy or West 105+205/206 (which can blush and bloom). Mr. Stock's epoxy fill videos carry a recommendation to move from Z-Poxy to SilverTip or other blush/bloom-free epozy. West, Maas, System 3, and other industrial brands of epoxy surfacers will note 'blush and bloom-free' where appropriate. Finally, for those that have used Z-Poxy without issue, this is a very body-chemistry-dependent issue. If no issues have surfaced on existing instruments, I would do nothing other than switch to a non-blushing/blooming filler on any new work. |
|
| Author: | bcombs510 [ Sun Jun 11, 2023 9:35 am ] |
| Post subject: | Re: finish blush |
Fascinating! Sent from my iPhone using Tapatalk Pro |
|
| Author: | flemsmith [ Sun Jun 11, 2023 1:08 pm ] |
| Post subject: | Re: finish blush |
Coupla que's I didn't answer...yes the white purfling is plastic, Pretty sure I did the big end wedge with titebond orig, including the purfling. Never used the blacklight before looking for glue edges. Body on #4 looks pretty clean, including the rosette and end stripe. Neck is a mess, I've still got more prep work to do. Roy |
|
| Author: | doncaparker [ Sun Jun 11, 2023 1:30 pm ] |
| Post subject: | Re: finish blush |
Woodie-- When I use epoxy, I use Silver Tip and avoid ZPoxy for the reason you cite (amine blush). So, my question is more for curiosity, not for my own personal use. Roy's guitar shows a problem at the tail wedge. That doesn't see like the sort of spot where the player's sweat will touch the finish all that often, compared to the neck and the bass side lower bout front edge. When Greenridge spotted these sorts of amine blush problems, did they tend to manifest in high handling areas, or everywhere? Again, just curious. You can't learn too much about the finishing process, particularly the things that can go wrong. Thanks for raising awareness of this issue. |
|
| Author: | flemsmith [ Sun Jun 11, 2023 3:23 pm ] |
| Post subject: | Re: finish blush |
Woodie, My fault for naming this thread blush; I've since been corrected in that my particular issue is more of a delam solely at the wood/purfling interfaces where I've used titebond glue instead of CA and then directly to lacquer with no sealer of any sort. In the picture I posted, there are light reflections outside that interface that are not really there in an accurate photograph. If it matters, I am using West 207 rather than Zpoxy for pore fill on this, my 4th guitar on which I have yet to start lacquer. I have not (yet) seen any issue on the finish of #3 (which I've been playing for well over a year) at the edge of the lower bout where my arm rests as I play. My original question related to a seal coat at least in those areas as a safety measure for the delams. Thanks for the inputs. I decided to try West systems after reading earlier statements about Zpoxy. Finishing has been a challenge for me, although the results on #3 are the best I've done so far largely due to inputs from this forum. Roy |
|
| Author: | Woodie G [ Mon Jun 12, 2023 6:48 am ] |
| Post subject: | Re: finish blush |
We saw separations away from wear areas, although the overwhelming number of issues were on neck and body contact areas. The tail graft area seems like one where amine blush and bloom would be tougher to remove than elsewhere, but given the sample size we dealt with, about the only definite conclusions reached were 1) Z-Poxy separation from sealer/top coats is an issue for some players, and b) SilverTip/other non-blush/non-bloom epoxies appear far less likely to see separations thought to be related to that residue. Since going to SilverTip, Greenridge finishes have been bullet-proof in service with Mohawk mid-VOC vinyl and classic instrument lacquer. |
|
| Author: | Mike OMelia [ Mon Jun 12, 2023 9:21 am ] |
| Post subject: | Re: finish blush |
Woodie, Thank you. I am going to be switching to Silver Tip. I have noted random discolorations (very occasionally). I have often thought (and still believe) this is related to applying Mohawk too soon and not cleaning surface adequately. Mostly, I see these on the back. What you say makes sense when joined to my experience with Z-Poxy. Mike Which hardener do you recommend? (fast/slow) |
|
| Page 2 of 2 | All times are UTC - 5 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|