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French polishing - final steps
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Author:  Ti-Roux [ Sat Jun 25, 2011 10:33 pm ]
Post subject:  French polishing - final steps
Hi everyone!

I'm finishing a ukulele with french polish method. It's my first attempt at FP.
I now have a nice and shinny finish all around the instrument, but still need a bit of leveling and final polish... here is the problem.

I already sanded (dry and wet) to level the finish, but ended with big scratches that took many sessions to fill... Then I tried to final sand with very fine sandpaper.. 800, 1000, 1500, etc... But I can't achieve a nice surface (it makes more scratches than everything else). The surface is better when I just french polish.

So... what am I doing wrong with the leveling/final sanding?
Do I really need to final sand? Can I just continue to french polish, adding less and less shellac?

Thanks a lot!
Francis
Author:  Matt Shumway [ Sat Jun 25, 2011 10:56 pm ]
Post subject:  Re: French polishing - final steps
I only ever sand it with 1200 grit, and only lightly. Once that's done I take my pad and start buffing it and any roughness caused by the sandpaper is gone within moments.
Author:  DennisK [ Sat Jun 25, 2011 11:07 pm ]
Post subject:  Re: French polishing - final steps
Ti-Roux wrote:
Can I just continue to french polish, adding less and less shellac?

Yep, that's the way I did it on my one attempt so far, although most of it ended up sinking into the pores and dulling down over the next week or so as it had time to fully dry out gaah But assuming you've got a good base, that produces a more beautiful sheen than either satin or gloss done with abrasives, IMO. It's one of the reasons I prefer FP over lacquer and the like. Mine does have some areas that I got filled properly, and retained that original beauty. Can't wait until I can reliably achieve it all over :)
Author:  WaddyThomson [ Sat Jun 25, 2011 11:52 pm ]
Post subject:  Re: French polishing - final steps
After you have a good body of shellac on the guitar, you should thin your shellac to something like a 1 lb cut, or less, and do glazing sessions. Glazing is just alcohol and shelllac, in small amounts on the muneca. Glazing strokes are straight, and recommended to go in one direction only, alternating in each session. I sometimes go both directions, though, and can't tell the difference. The key is light straight strokes with some pressure. This should level the shellac ridges. I assume you have been spiriting off after every body session after the first. This is the process that levels the ridges left from the body sessions.s
Author:  David Wren [ Sun Jun 26, 2011 8:49 am ]
Post subject:  Re: French polishing - final steps
One of the many valid ways to go about the final stages of French Polishing ... is to use MicroMesh for the final sanding (up to 12,000 grit if you like) then either glaze with alcohol and a bit of thin shellac (1/2 pound or 1 pound) or hand buff it with Novus polish (available at plastics supply stores).
Author:  WaddyThomson [ Sun Jun 26, 2011 9:53 am ]
Post subject:  Re: French polishing - final steps
If you are a purist, no abrasives are used in French polishing outside of pumice. Not saying I conform to the purist life.
Author:  David Newton [ Sun Jun 26, 2011 1:40 pm ]
Post subject:  Re: French polishing - final steps
I'm a purist with a cork block. beehive

Pumice is a pretty serious abrasive to say "no abrasives other than pumice"
I use those very fine abrasive cloths that Stewmac sells, and Maquires #7, and even then I like best a straight polishing out with shellac only.

Dang customers want to comb their hair in my guitars.
Author:  WaddyThomson [ Sun Jun 26, 2011 2:19 pm ]
Post subject:  Re: French polishing - final steps
I do use a little Meguires at the end of the process. It'll let them comb their hair.
Author:  woody b [ Sun Jun 26, 2011 2:41 pm ]
Post subject:  Re: French polishing - final steps
TiRoux wrote:
................................................................................................................................................................
I already sanded (dry and wet) to level the finish, but ended with big scratches that took many sessions to fill... Then I tried to final sand with very fine sandpaper.. 800, 1000, 1500, etc... But I can't achieve a nice surface (it makes more scratches than everything else).....................................................................................................................................................................



I'm not a French Polisher, but if you're getting big scratches from finer grits of sandpaper I suspect you're either letting finish ball up on the paper causing the deep scratches, and/or you're using too much pressure when sanding. Light pressure (almost no pressure at all), fresh paper, and keeping the surface clean are keys. Let the abrasives do the work. Sanding a finish that isn't cured long enough can also cause similar problems.

Again, I'm not a French Polisher.
Author:  David Newton [ Sun Jun 26, 2011 6:59 pm ]
Post subject:  Re: French polishing - final steps
You don't have to be a french polisher to know what abrasives can do.
I know different brands of papers can have different grit sizes unintentionally mixed into a finer graded paper, so quality is important.
Micro mesh has a good reputation, though I've never used it.
I like the polishing cloths that stew mac sells, and there are a range of grits, the coursest one is the one I use most, the finer ones hardly do any work at all. They can be cleaned and used over and over.
Author:  Ti-Roux [ Sun Jun 26, 2011 9:21 pm ]
Post subject:  Re: French polishing - final steps
Thanks to you all, guys!

I did sand, lightly and with soaky water, with 1500 grit to level the finish, then did a final session, to fill the micro scratches.
I now have a nice surface ready for final steps. I will cut my mixture to 1 pound, and try to achieve a high gloss with the rubber.

For those who use micro mesh... what your process? I mean, when do you begin to use them, which grit, and wet or dry?

Thanks again!
Francis
Author:  Mark Groza [ Mon Jun 27, 2011 6:22 am ]
Post subject:  Re: French polishing - final steps
After building up the finish, i level sand up to 1200 grit with olive oil, then finish up with french polish glazing coats for the shine. Doesn't need any further polishing as that's what's nice about french polishing.
Author:  fransoos [ Mon Jun 27, 2011 9:42 am ]
Post subject:  Re: French polishing - final steps
I am not a pro but getting some good results using 2000 grit wet sanding (adding some
soap to the water).
Sand with no pressure and the surface becomes as smooth as the cheeks of a baby'.
Author:  Michael Lloyd [ Mon Jun 27, 2011 12:01 pm ]
Post subject:  Re: French polishing - final steps
WaddyThomson wrote:
After you have a good body of shellac on the guitar, you should thin your shellac to something like a 1 lb cut, or less, and do glazing sessions. Glazing is just alcohol and shelllac, in small amounts on the muneca. Glazing strokes are straight, and recommended to go in one direction only, alternating in each session. I sometimes go both directions, though, and can't tell the difference. The key is light straight strokes with some pressure. This should level the shellac ridges. I assume you have been spiriting off after every body session after the first. This is the process that levels the ridges left from the body sessions.s


There is plenty of information on how to french polish. Here and on the web. If there is one thing that is most important and should be part of every session, I agree with Waddy "spiriting off after every body session".

Once I've done the pore filling the pumice goes away. I've never had to level sand unless it was a repair job.
Author:  David Wren [ Mon Jun 27, 2011 9:33 pm ]
Post subject:  Re: French polishing - final steps
If you're looking for a French Polish schedule that involves micromesh, you could try something like this. This schedule uses a less than 1 pound cut (using the theory that many thin coats makes a tougher finish). And yes, this is not for the purists out there, but I do know some professionals who use a similar schedule and get a result that I would put beside anyone's finish. This, of course, is just one way of doing things.

-two sessions (after prep/filler) then level with 1500
-six more sessions then sand with 2400 & 3600
-two sessions ... leave for a few weeks
-sand progressively from 4000 to 12,000
-hand buff with Novus or glaze with fad and alcohol
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