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Thread: High gloss sanding tip

  1. #1
    Join Date
    Jan 2012
    Location
    NW Louisiana
    Posts
    482

    High gloss sanding tip

    This project represents several firsts for me -

    1) First acoustic guitar from scratch. I've replaced tops, backs, bridges, saddles, nuts, done inlay, repairs, etc. but this is the first one from scratch - resawed the wood, bent the sides, etc.

    2) First time to do a French polish from the start and not just a repair.

    3) First time I've made this many mistakes in a project and kept going, trying to figure out how to successfully fix what I've done and trusting it's still going to work out ok.

    So here's the sanding tip I learned a long time ago and I have no idea if it's something I read, something I figured out, or even if it's common knowledge - It takes twice as long sanding with the next grit as you spent sanding the previous grit.

    What do I mean by that? If you're sanding a finish, or even bare wood, with say 220 grit and you move to 320 grit, then if you sanded for 5 minutes with 220 then it's going to take 10 minutes of sanding with 320 to remove all of the 220 grit scratches.

    Right now I'm wet sanding the guitar that has a very thin film of shellac and when I wet sand with 320 it takes no more than a minute to do the back twice. When I switch to 400 I sand for about 2 minutes although I don't time it. Basically I sand the back twice, wipe the slurry off, blow it dry to see if I have even coverage of sanding, and then switch to 400 and do the same thing. Only now with 400 I do the back about 4 times. When I switch to 500 I'll do it 8-10 times. When I get to 600 I'll be doing it at least 15 times. By the time I get to the 1200/1500/2000 I'll probably keep going until it looks right and then switch to Micromesh.

    I haven't made it past 500 yet because I keep seeing where I'm getting too close to burning through to the Mahogany so I've had to stop and shellac again several times. So when I get to the finer grits it's necessary to judge how much finish is left so I don't go through on the polishing later.

    Anyway, it's a sanding tip I've passed along to lots of folks so while I'm waiting on shellac to dry it seemed like a good time to post this (only takes a few minutes to dry before I can sand again).

    Wet sanding
    001 - Wet sanding back, French polish.jpg

    002 - Wet sanding back, French polish.jpg

    Fresh shellac
    003 - French polish back.jpg

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
    YouTube Woodworking Channel for David Falkner (just search for me by name)
    Romans 3:23

    Etsy shop - CurlyWoodShop

  2. #2
    Join Date
    Jul 2012
    Location
    Punta Gorda, FL
    Posts
    2,149
    Yeah, I agree but sometimes I think it just seems like it takes longer and longer as you move through the grits because it's so tedious.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  3. #3
    Join Date
    Jan 2012
    Location
    NW Louisiana
    Posts
    482
    Can't argue with that, Julie. How are your builds coming along? I haven't kept up so no idea what you're working on...

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
    YouTube Woodworking Channel for David Falkner (just search for me by name)
    Romans 3:23

    Etsy shop - CurlyWoodShop

  4. #4
    I haven't made it past 500 yet because I keep seeing where I'm getting too close to burning through to the Mahogany so I've had to stop and shellac again several times. So when I get to the finer grits it's necessary to judge how much finish is left so I don't go through on the polishing later.
    Well then you need to be applying more coats initially so you don't have to re-apply. As soon as you re-apply all of your sanding effort is gone.

  5. #5
    Join Date
    Jan 2012
    Location
    NW Louisiana
    Posts
    482
    Couldn't agree more, Leo. But like I said, first time to do a French polish finish from the ground up. Didn't have to worry about it with some of the repairs I've done in the past because they were just spot areas on furniture. I thought I had plenty on when I began sanding only to find I didn't. I'm probably too concerned about keeping the finish thin but it's a learning curve that's coming around.

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
    YouTube Woodworking Channel for David Falkner (just search for me by name)
    Romans 3:23

    Etsy shop - CurlyWoodShop

  6. #6
    Join Date
    Mar 2015
    Location
    SE Michigan
    Posts
    1,536
    I don’t understand why after a french polish you would need to start sanding at 220. A good french polish leaves a smooth, gloss finish. I might buff out with a very high grit wet/dry, or polishing compound, at most.

    If, on the other hand, I happen to stop the pad and leave a blotch, I completely sand back and restart. What is your reason for using the lower grit papers after the french polish?

  7. #7
    Join Date
    Jan 2012
    Location
    NW Louisiana
    Posts
    482
    Oh, I'm not sanding with 220, Phil. That was a reference to bare wood or like when I spray Nitro where I usually sand the sealer with 220 Tri-M-ite and then move on to 320...

    My starting grit for the shellac on this guitar is 400 although I have used 320 and 360 a couple of times trying to get a feel for where to start.

    David
    David

    Nothing to do with woodworking at all, just our music at church (I'm the guy with the Koa Takamine) - Go to YouTube and search for Airline Baptist BC - enjoy!
    YouTube Woodworking Channel for David Falkner (just search for me by name)
    Romans 3:23

    Etsy shop - CurlyWoodShop

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