Finishing Frustration

The Achilles' Heel of Luthiery
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Stray Feathers
Posts: 540
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Finishing Frustration

Post by Stray Feathers »

I've been sanding and polishing two guitars and two ukuleles lately, and am frustrated with inconsistency, and even more with scratches. I sanded the wood to 220 at least and in some cases maybe 320, used Aquacoat and sealer and light sanding before and after, wiping with naphtha and tack cloth etc., and sprayed lacquer. The lacquer coats in some cases were very glossy, sometimes a little more orange peel. After curing for six weeks or more, I levelled with 600 grit wet, then 800 and 1000 wet until I could see no glossy bits left, then 1200 and 1500 wet, and then Micro Mesh 6000, 8000 and 12000. I went back to 1000 wet a couple of times and went back through all the grits but these scratches still remain. The scratches you see in the photo do not appear until after the Micro Mesh 8000 or 12000. I don't know whether the scratches are in the wood ( in which case 220 is not fine enough?) or in the lacquer somewhere, maybe picked up during sanding. After this, I used Menzerna medium paste and then fine, both of which are supposed to be good after only 1000 or 1500 grit sanding. I also used buffing wheels with Menzerna medium and fine abrasive on them.The scratches are somewhat inconsistent with some instruments pretty good, but I can't get a consistent mirror finish. I may keep sanding back on this most recent guitar to see how far I have to go to fix it, knowing I may go through the lacquer - which means I wait until spring to spray again. I found John Hall's recent finishing videos very helpful in reassuring me that what I was doing, and what things looked like through the process, were pretty normal - until the scratches appear. Any insights appreciated - Bruce W.
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tippie53
Posts: 6826
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
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Re: Finishing Frustration

Post by tippie53 »

those are in the finish
what are you using for buffing and polish
I have a few vids out on this subject

I stopped using micro mesh and went with asilex but you need to buff and polish. I think this unit
will help
https://www.amazon.com/Polisher-SPTA-De ... 690&sr=8-7

I use klingspore sand paper up to 2000 grit
then asilex once I am done that process I start buffing then polish

I use a shop fox buffing wheel and the dual action buffer.

Your close you just need the final steps. Look at auto detail vidios on you tube or if you can find jeff jewitt vids
https://www.youtube.com/watch?v=phrPStMQEAM
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Stray Feathers
Posts: 540
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Finishing Frustration

Post by Stray Feathers »

John, thanks for your quick reply - I am going out to the shop soon to look at this again. I do use Klingspor paper up to 1500, have not looked for 2000 but will. After that Micro Mesh, then Menzerna 2L medium paste, hand rubbed with a cloth, followed by Menzerna 16 fine paste and in the end Menzerna polish (which is supposed to be a "swirl remover" but does not get scratches).

https://www.woodessence.com/Buffing-Pol ... hing-Paste

The Menzerna 2L says it can be used after sanding to 1000, and followed with the finer 16. The 16 says it can be used alone following sanding to 1500. Then I use a Shop Fox arbour with 12" wheels, and Menzerna medium and fine stick abrasives. I tried using Micro Mesh discs 6000 to 12000 (bought from Lee Valley) wet, on a random orbit sander, but got some curly scratches and am not inclined to try it again. I've considered an auto-type buffer and will look into it. How often should the stick abrasive be applied to the cloth buffing wheels?
tippie53
Posts: 6826
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
Contact:

Re: Finishing Frustration

Post by tippie53 »

the buffer will help your finishing a lot
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
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