Why sand grainfiller to bare wood? (probably noob question)

Discussion in 'Finely Finished' started by Polderpatat, Jul 28, 2021.

  1. Polderpatat

    Polderpatat TDPRI Member

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    Hey

    I've read a lot here about grain fillers and everyone seems to accept that after a grainfiller is applied, you should sand it down to bare wood.

    I don't see why I shouldn't "just" sand it till the whole surface is smooth. I'm going to have it finished with opaque colors, so why sould I bother sanding it down to bare wood?
    I've used Rustins oil-based grainfiller. I've got much of the excess off just by whiping across the grain.
    It did leave a thin layer that reminds me of a sanding sealing coat.

    SO long story short, why sand a grain filler not to a smooth surface but really down to the wood? (no idea if this is a noob question)
     
  2. Boreas

    Boreas Poster Extraordinaire Silver Supporter

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    If you don't sand it down to the wood, you will be finishing the sealer, not the wood. It will wash out the attractive grain of the wood.
     
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  3. Winky

    Winky Tele-Meister

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    Even if finishing with a solid colour, you'll perhaps want the primer or finish to be in direct contact with the wood. Grain filler is not necessarily designed to provide the same adhesion to the wood. It might be OK, but why use it in a manner that is not as-intended?
     
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  4. Polderpatat

    Polderpatat TDPRI Member

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    can you explain what you mean whit wash out the grain? I don't bother with the grain because it will be a solid opaque colour ontop (RAL 5011 to be specific). So I'm only conearned by adherence and not with the look of the grain.
     
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  5. Boreas

    Boreas Poster Extraordinaire Silver Supporter

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    See #3 above.

    I didn't realize you were going opaque. Washing out the grain in this context would mean the filler would partially obscure it. It would look like crap if you weren't going opaque.
     
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  6. Sax-son

    Sax-son Tele-Afflicted

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    You don't sand all the way down to the wood. First, you work in with a squeegee or cloth and if need be, you lightly sand to get all the bumps and high spots down. The sanding sealer is what takes all the sanding activity once the grain filler has been applied. You may have to do a second coat if the sanding sealer shrinks on you. Once the sanding sealer has covered all the divots and is smooth, then you apply your color coat. It is a multi step process to painting. The trick is not to build it up too thick. The lighter the finish, the better the tone in my opinion.

    PS: There are different grain fillers that won't wash out or cover the grain. Don't use any of the white of black ones if you are looking for a natural look.
     
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  7. Polderpatat

    Polderpatat TDPRI Member

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    Maybe I'm thinking to simplistic but when the pores are filled and you put any product on it, it must stick to that as well no?

    My main problem now is that sanding the filler to the wood takes long, and I did obscure some new pores when going just a bit to harsh on some area's:oops:. Would be nice if all that work and risk wouldn't be necessary :D
     
  8. Polderpatat

    Polderpatat TDPRI Member

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    Is a sanding sealer always required? There will be a 2k primer and after that 2k automotive paint put on the body by a bike painter.
    I thought the sealers purpose would be obsolete with such a primer and/or with the (very thin) top covering of the fillers carrier.
     
  9. lammie200

    lammie200 Friend of Leo's

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    There are two types of woods - open pore/open grain and closed pore/closed grain. Open refers to voids between grain lines. Closed refers to very small or no appreciable voids between grain lines. If you want a totally smooth finish you will have to fill the voids in open pore/open grain woods.

    Ash is open pore/open grained. Maple is closed pore/closed grain.

    OK, nevermind.
     
  10. Sax-son

    Sax-son Tele-Afflicted

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    Sealers just allow for the wood to become smooth and level. How you get there can be done in multiple way. However, you don't want the paint to be to thick, otherwise it chokes off all the resonance.
     
  11. Polderpatat

    Polderpatat TDPRI Member

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    Here's a picture of where I'm at now. The grain is filled with a natural coloured filler (the rustins one). but the wood still gives that "wetted/coated" look. So I assume there is still a fine layer actually on the wood itself.
    [​IMG]
     
  12. Polderpatat

    Polderpatat TDPRI Member

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    don't bother with chocking the tone, the floating bridge does that already :lol:
     
  13. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    In my case that is the same thing. I sand level to the wood but leave the filler in the pores, that is the whole idea. I use finishing resin for pore filling which actually could be a finish in itself but I cannot imagine wanting to leave other fillers like pastes on the surface of the wood.

    I also usually apply one more coat of my finishing resin very highly thinned with DNA - it soaks into the wood just like the alcohol does but carries enough of the epoxy to bring out figure. Its particularly vivid with wood with lots of chatoyance.

    Here is mahogany, a very porous wood, first coat of Zpoxy going on

    IMG_5140.JPG

    Sanded back level to wood, a thin coat going on for enhancement

    IMG_5143.JPG

    Sanded back level again

    IMG_5148.JPG

    With finish. The pores are filled and won't shrink back with age

    IMG_5198.JPG
     
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  14. Sax-son

    Sax-son Tele-Afflicted

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    A picture is worth a thousand words!
     
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