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| Author: | MaxBishop [ Sat Dec 21, 2019 10:46 am ] |
| Post subject: | Partial finish restoration |
Hi All, I have a project that I have not dealt with before. I received back a guitar I built for a customer a few years ago. I plan to replace the neck, but the finish on the top upper bout has been damaged and in some cases almost completely removed. I don't know how this happened. It looks like someone dumped acetone on it(!). The guitar is a Flamenco blanca and the finish is hand applied spar varnish. I once read an article somewhere about doing such a partial finish restoration by prepping the damaged areas and applying new finish and blend into the undamaged finish by successively thinning subsequent coats. I do not have the article nor do I remember where it came from. Anyone have experience with with something like this? I would greatly appreciate any input in this regard. Thanks, Max Bishop |
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| Author: | Pat Foster [ Sat Dec 21, 2019 11:04 am ] |
| Post subject: | Re: Partial finish restoration |
Max, It's been some years ago now, but I had success refinishing part of the side of a guitar finished with Epifanes. I don't recall all the details, but I feathered the area and mixed acetone into the varnish, about 5% if I recall, to help the new finish bite. Final sanding went down to 12000 with MicroMesh. Buffer took care of the witness lines. |
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| Author: | Barry Daniels [ Sat Dec 21, 2019 11:13 am ] |
| Post subject: | Re: Partial finish restoration |
Varnish does not burn in so it is difficult to repair. I would do a full refinish, or at least the sides. |
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| Author: | alan stassforth [ Sat Dec 21, 2019 11:46 am ] |
| Post subject: | Re: Partial finish restoration |
Sorry about that, Max. I agree with Barry. I can't believe spar varnish would do that, so, something must have happened to the guitar. Problems down the line after a build are the reason I don't sell my builds. Alan |
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| Author: | Clay S. [ Sat Dec 21, 2019 12:22 pm ] |
| Post subject: | Re: Partial finish restoration |
Since it is a varnish finish you might research violin finish repair. Spar (long oil) varnishes tend to remain comparatively soft, so you will want to recoat with the same product originally used (best) or one with matching properties. This video may offer some help: https://www.youtube.com/watch?v=jbE-Sl_IIDM |
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| Author: | B. Howard [ Sat Dec 21, 2019 1:43 pm ] |
| Post subject: | Re: Partial finish restoration |
If it is a true "Spar" varnish it should be able to be wetted out and blended with new. Typically gum spirits or turpentine are used with traditional spar varnish. |
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| Author: | MaxBishop [ Mon Dec 23, 2019 1:35 pm ] |
| Post subject: | Re: Partial finish restoration |
Hi Brian, Yes, it's Petit Captain's Varnish. What do you mean by "wetted out"? |
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| Author: | B. Howard [ Tue Dec 24, 2019 7:41 am ] |
| Post subject: | Re: Partial finish restoration |
One of the first steps to a seamless repair of these materials is re-hydrating the original film or "wetting out" as they used to say in the trade. On old Nitro we typically spray a bit of retarder to prep the old material to bond with the new at a molecular level. In the case of a real varnish that would entail cleaning any contaminates off the surface followed by a thorough scuff with some fine steel wool ( or equivalent) and then gently moistened with spirits (typically gum turpentine). This returns the original film to the state it would have been in at any re-coat window in the original finish schedule. This then allows the resins to amalgamate in the same manner as original. The problem will be if you do not have the exact same varnish..... due to variables in varnishes the coloration between brands is considerable and even differences between batches can be quite noticeable. |
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| Author: | MaxBishop [ Tue Dec 24, 2019 2:32 pm ] |
| Post subject: | Re: Partial finish restoration |
Thanks to all for your input. perhaps I'll post a picture of the finished (or "refinished") product. Max |
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