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Thread: How to: Rehab a damaged surface...

  1. #1
    Join Date
    Apr 2019
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    Default How to: Rehab a damaged surface...

    Purchased a "B-Stock" Ohana CK 50G (Cedar top, Redwood back and sides). It's a gloss finish and has some finish problems. Described by seller as having a scratchy finish with a few tiny finish bubbles.

    As a furniture woodworker I'd use 0000 steel wool with some wax to try to buff out a lightly scratched surface. Just wondering how others might have tired to brighten the surface of their 'well worn' uke surfaces.

    No pics yet. Awaiting delivery. FWIW, scratches don't go deep to the solid wood surface. (I'm assured.)

  2. #2
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    For myself, I just take scratches and such as being part of the life of an instrument. The 50G is a nice instrument congrats!

  3. #3
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    My local guitar tech says if nothing wrong with sound, leave it. Uku is not furniture, check sound first.

  4. #4
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    Quote Originally Posted by yahalele View Post
    My local guitar tech says if nothing wrong with sound, leave it. Uku is not furniture, check sound first.
    Unfortunately for your guitar tech I own the 50G and not her/him :-) If I want to refresh the surface I don't need permission. If there are substantive cautions or warnings, those would be helpful and beneficial.
    Checking the sound "first" doesn't make sense, unless you're implying that a 're-finishing' of the surface would affect the sound.
    The finishing techniques for ukulele are very similar to that of fine furniture. While you're statement "Uku is not furniture... is obvious, it adds nothing to this conversation or my inquiry. :-)

  5. #5

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    Without knowing what the finish is, it is hard to make good recommendations. However, since it is gloss I will make the (not necessarily correct) assumption that this is a film finish.

    I might start with some rottenstone and some water as a lubricant and try rubbing out some of the finish. Rottenstone should leave a pretty glossy finish which means that it may not be coarse enough to get out your scratches and bubbles. Then again, it may be all that you need.

    If that wasn't enough, I might progress to a fine pumice.

    If still not enough, I would probably start with wet/dry 1000, working down from there until I find the finest grit that got to the problem. You will then need to progress back to the finer grits to obtain the sheen that you would like. However, don't go to far and rub through the finish. Then you will have problems!

    However, I find I agree with others - finishes get scratched, etc. It is a ukulele and meant to be played. I am doubtful this process is worth the pretty substantial effort.

    Others may have other preferences for rubbing out the finish.

    And of course, your level of skill in using these polishes have a lot to do with the outcome. I am not sure I would be up for the challenge. But that is just me.

    Oh, final thought... wax may be enough to fill the scratches and give you a nice look, but this would have to be reapplied periodically, and entirely removed occasionally to prevent build up.

  6. #6
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    Quote Originally Posted by eclipsme View Post
    Without knowing what the finish is, it is hard to make good recommendations. However, since it is gloss I will make the (not necessarily correct) assumption that this is a film finish.

    I might start with some rottenstone and some water as a lubricant and try rubbing out some of the finish. Rottenstone should leave a pretty glossy finish which means that it may not be coarse enough to get out your scratches and bubbles. Then again, it may be all that you need.

    If that wasn't enough, I might progress to a fine pumice.

    If still not enough, I would probably start with wet/dry 1000, working down from there until I find the finest grit that got to the problem. You will then need to progress back to the finer grits to obtain the sheen that you would like. However, don't go to far and rub through the finish. Then you will have problems!

    However, I find I agree with others - finishes get scratched, etc. It is a ukulele and meant to be played. I am doubtful this process is worth the pretty substantial effort.

    Others may have other preferences for rubbing out the finish.

    And of course, your level of skill in using these polishes have a lot to do with the outcome. I am not sure I would be up for the challenge. But that is just me.

    Oh, final thought... wax may be enough to fill the scratches and give you a nice look, but this would have to be reapplied periodically, and entirely removed occasionally to prevent build up.
    A thoughtful reply...thanks for taking the time. Those kind of options are helpful to my thought process. FWIW, scratches, etc. don't bother me as much as my question might imply! I'm anticipating light surface 'stuff' that, with a light buffing could be mitigated. If not, I'm NOT going into a full restore mindset :-). Thanks again.

  7. #7
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    OP
    Received 50 G yesterday. Very nice. Surface scratches very shallow and pretty much all over the back. Not at all disappointed. Grabbed some "Tom's of Maine" toothpaste and a wet piece of old T-shirt. Gentle rubbing using the paste as the 'abrasive and with a few dozen swirls over small sections and the scratches were gone. And it smells minty fresh! Larger chips were more of an issue. Four "bubbles" where gloss had separated from wood surface. Two of those had gloss flaked away. Used thin CA glue to fill the bubbles and seal against additional separation. Am using a medium viscosity CA (Medium Brown by StarBond)to little-by-little fill in the chipped section. Using the tip of a round toothpick and needle to add tiny drops, letting each dry completely before adding the next. This should save the surface from any more separation.
    Thanks to all for the encouragement both public and private :-)

  8. #8
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    Quote Originally Posted by Web_Parrot View Post
    Grabbed some "Tom's of Maine" toothpaste
    Do you get better tone with the fluoride or non-fluoride flavors?

    It sounds like you may be beyond this, but StewMac has a video on filling small chips in a guitar finish with CA:

  9. #9
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    Quote Originally Posted by Arcy View Post
    Do you get better tone with the fluoride or non-fluoride flavors?

    It sounds like you may be beyond this, but StewMac has a video on filling small chips in a guitar finish with CA:
    I watched the StewMac video and it's similar to how I used the razor blade. However, I didn't waste my time putting a "hook" on the edge of the razor blade. [That's a scraper technique used in wood working to curl the wood shavings up and away to prevent splintering.] Using it on CA provides no advantage and actually takes away being able to flip the blade around to cut with both sides. Here's what I did:

    I used a thin CA glue to wick under the gloss coat and then after a 24 hour dry (no accelerator) gradually added some StarBond medium viscosity CA that is tinted brown. At first I flooded the open area with a good sized drop, and after an 8 hour cure, I added small drops to bring the glue just above the final finish level.

    After it thoroughly dried, I took a straight-single-edge razor blade, taped the edges of the blade and used the center sharp section like a scraper. I used different thicknesses of tape to bring the blade closer and closer to the original finished surface. Then I took 1200 grit wet paper mounted on a large eraser (solid, flat surface) and wet sanded the dried CA.

    To get the gloss back I used an old t-shirt with dabs of toothpaste (Tom’s of Maine, with fluoride, spearmint flavored!) It’s a mild abrasive, perfect for the final gloss and minty fresh aroma :-) I think I mentioned that I used the toothpaste rub out the other scratches. All in all I’m please with the results!

    Finish Before.jpg
    Finish After.jpg
    Last edited by Web_Parrot; 09-11-2019 at 11:36 AM. Reason: Photos

  10. #10
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    Quote Originally Posted by Web_Parrot View Post
    I watched the StewMac video and it's similar to how I used the razor blade. However, I didn't waste my time putting a "hook" on the edge of the razor blade. [That's a scraper technique used in wood working to curl the wood shavings up and away to prevent splintering.] Using it on CA provides no advantage and actually takes away being able to flip the blade around to cut with both sides. Here's what I did:

    I used a thin CA glue to wick under the gloss coat and then after a 24 hour dry (no accelerator) gradually added some StarBond medium viscosity CA that is tinted brown. At first I flooded the open area with a good sized drop, and after an 8 hour cure, I added small drops to bring the glue just above the final finish level.

    After it thoroughly dried, I took a straight-single-edge razor blade, taped the edges of the blade and used the center sharp section like a scraper. I used different thicknesses of tape to bring the blade closer and closer to the original finished surface. Then I took 1200 grit wet paper mounted on a large eraser (solid, flat surface) and wet sanded the dried CA.

    To get the gloss back I used an old t-shirt with dabs of toothpaste (Tom’s of Maine, with fluoride, spearmint flavored!) It’s a mild abrasive, perfect for the final gloss and minty fresh aroma :-) I think I mentioned that I used the toothpaste rub out the other scratches. All in all I’m please with the results!

    Finish Before.jpg
    Finish After.jpg
    Wow - that looks perfect! Had I not seen the 'before' photo, I never would have guessed there was a repair.

    You have clearly taken the time and with great patience to finesse the surface back to this wonderful state

    Thanks for sharing both the process and the photos!

    I hope the uke lives up to all your expectations and is fun and pleasing to play
    -Joe......Have uke, will travel...

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