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Dull spot with friction polish

Discussion in 'Woodturning Discussion Forum' started by John Hicks, Jul 29, 2020.

  1. John Hicks

    John Hicks

    Joined:
    Jan 23, 2020
    Messages:
    149
    Location:
    Hoodsport, Washington
    Ok bowl gurus: I love to use shine juice over a shellac sealer on bowls. But I cannot seem to get the very center of the bowl to finish without a dull spot. I added a pic and I hope you can see the center spot I'm talking about. I've tried running it faster while finishing the center spot; but that doesn't seem to do anything. I know there's a trick and you guys know what it is! It's maddening! This bowl is local big leaf maple, after spinning on 4 or five coats (this is before final sanding and buffing), you can make out the dull spot in the center that I always seem to get.

    IMG_7641.JPG
     
  2. Brandon Sloan

    Brandon Sloan

    Joined:
    Mar 7, 2019
    Messages:
    116
    Location:
    Victoria, Texas
    Beautiful piece of wood! The dull spot doesn’t jump out at me as much as the sanding scratches. Shiny finishes will highlight all the imperfections in the surface. Surface prep is critical in getting a nice even finish. This was my process for learning to turn bowls.
    1. Shape and even wall thickness. You should be shooting for a nice catenary curve, with a base that is roughly 1/3 the diameter of the rim.
    2. Sanding, this step is made easier after you master step one. If you are hand sanding with the lathe turned on, you will need to stop the lathe and sand across the rings before moving up to the next grit. (I power sand so I’m just repeating what others have said)
    3. Finishing, I’m still learning and experimenting. Here’s what I’ve learned so far. You’ll spend just as much, if not more time sanding and finishing as you do turning. (If you want a good, durable finish)
    There’s plenty of folks more experienced than me that will probably explain things better than me. Just from a relative new turner, sometimes we have to take a step or two back before we can move forward. Good luck and let us know how it turns out.
     
    Ron Solfest and John Hicks like this.
  3. John Hicks

    John Hicks

    Joined:
    Jan 23, 2020
    Messages:
    149
    Location:
    Hoodsport, Washington
    They look like sanding marks, but are left by the paper towel in the shine juice. I sand to 600 then use a white synthetic pad, followed by a final coat of friction polish.
     
  4. Brandon Sloan

    Brandon Sloan

    Joined:
    Mar 7, 2019
    Messages:
    116
    Location:
    Victoria, Texas
    I had the same problem. I was sanding to 600, tried sanding to 1200, nothing worked. The surface would look pristine until I applied the shine juice. I even thought the same thing, it must be the paper towel. So I switched finishes and the same thing would appear. That’s when I asked @hockenbery for some advice. I bought some hook and loop sanding disks for my drill and said goodbye to those annoying marks. I never sand past 320 anymore, unless I’m wet sanding my final finish. (Done by hand off the lathe) I could be wrong, but I suspect the shine juice is bringing out sanding marks.
     
    John Hicks likes this.
  5. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
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    Location:
    Lakeland, Florida
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    Could be sanding marks are now highlighted. Also can be drag marks in the finish. It is really hard not to leave marks in any finish applied while the lathe is running.

    Very few people are really good at Applying finish while the lathe is running- I’m not one of them.

    the final sanding, and buffing etc are best done in the direction if the grain off the lathe or with the lathe not running.
    Then any fine lines become invisible.

    you need to finish the finish and buff out the drag lines.
     
    Last edited: Jul 29, 2020
    Ron Solfest and John Hicks like this.
  6. Randy Anderson

    Randy Anderson

    Joined:
    May 25, 2019
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    Location:
    Eads, TN
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    I'm NOT and expert on finishes and am basic in what I use - walnut oil and sometimes danish oil. That's the limit of my finish expertise but, I did stop spin sanding early on. I see people do it all the time but I could never get rid of the spin sanding marks. I use 2" and 3" hook and loop abranet or pronet discs and almost never go beyond 400. If I do spin sand around the foot or rim I go back with hook and loop on my drill sander and make sure I get rid of the spin sanding marks. On just about anything I do I can see spin sanding trails even with 320 or 400 on things. I know there's a knack for how to do it but I don't have it.
     
    John Hicks likes this.
  7. Richard Coers

    Richard Coers

    Joined:
    Aug 14, 2009
    Messages:
    959
    Location:
    Peoria, Illinois
    If those are finish lines, you need something a lot softer to apply it, and I suggest a lot less juice in each application.
     

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