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Thread: shellac grain filler problems

  1. #1

    Default shellac grain filler problems

    Iím testing to see how well shellac works as a grain filler on Mahogany.

    I have brushed on several coats of 2# shellac using a foam brush. I have sanded between coats but Iím still getting those pins size shiny spots.
    At this point, Iíve sanded nearly threw the finish back to the wood, and those pin size divots are still there.

    Are these tiny low spots caused by air bubbles created with the foam brush I am using? I will spray whatever I end up using but I don't want to go to the trouble on a test piece.

    Thank You

  2. #2
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    Shellac isn't a grain filler.

    The low shiny spots are because shellac isn't a grain filler.

    The best way to remedy it is to use a grain filler and not use something that isn't a grain filler, eg shellac.

    Shellac is used in conjunction with other products to fill pores but it isn't the shellac filling the pores, it is the other products. Pumice is the traditional product, but all pumice does is grind wood fibers/particles off the surface of the wood and add them to/into the pores, slowly filling them with the wood/pumice slurry.

    Best way to skip this tedious and unnecessary step is to sand the wood with say 400 grit paper, leave the dust in the pores, then do a coat of shellac wet enough to wet all that dust in all the pores. It will be quicker and the end result is the same...although not quite as hard as with pumice...it will all shrink back though.......

    Ssssssssooooooooooo................................just use a commercial pore filler, or epoxy, or ca.

    Hope that helps.
    Last edited by Beau Hannam Ukuleles; 12-20-2018 at 06:29 AM.

  3. #3
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    Take a look here

    https://www.youtube.com/watch?v=EcRc1cJrgtU

    A variation on this is to wet sand with 1 lb cut or less. You can start with 220 and work up to 400. This makes the powder as you go rather than making the powder in advance. As you sand, add a little shellac or alcohol to the surface as needed to keep the slurry going. The best result as I recall is to let the surface harden between grits. Maybe a half hour so so. There will be a little shrink back over time but that's true with lots of pore fill techniques.

  4. #4
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    I tried this technique a couple of years ago and wasn't really satisfied with how it looked or worked. I never did get a good pore fill and ended up not selling the instrument but keeping it as a my own player. I love this instrument even if the finish turned out crappy (at least to my OCD eye). Below are before and after pictures. Note deep "pores" (crevasses?) remaining.

    DSCN7127.jpg DSCN7177.jpg DSCN7178.jpg

  5. #5
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    The wet sanding method can result in a very nice surface that is comparable in appearance to a sprayed and buffed finish but without the need to invest in costly equipment. Both of these were pore filled this way and finished with Tru-Oil to a smooth and glossy surface. I didn't mention it above but you can use Tru-Oil instead of shellac in the sanding phase, except on the few woods that inhibit drying of Tru-Oil. On the woods that have this issue, pore filling with shellac provides the necessary barrier coat between the wood and the Tru-Oil, allowing the oil to cure.




  6. #6

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    [QUOTE=sequoia;2119873]I tried this technique a couple of years ago and wasn't really satisfied with how it looked or worked. I never did get a good pore fill and ended up not selling the instrument but keeping it as a my own player. I love this instrument even if the finish turned out crappy (at least to my OCD eye). Below are before and after pictures. Note deep "pores" (crevasses?) remaining.
    /QUOTE]

    Wow, the instrument looks wonderful but yes the pores are not filled. Did they look filled before you started the final finish?

  7. #7

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    Quote Originally Posted by saltytri View Post
    The wet sanding method can result in a very nice surface that is comparable in appearance to a sprayed and buffed finish but without the need to invest in costly equipment. Both of these were pore filled this way and finished with Tru-Oil to a smooth and glossy surface. I didn't mention it above but you can use Tru-Oil instead of shellac in the sanding phase, except on the few woods that inhibit drying of Tru-Oil. On the woods that have this issue, pore filling with shellac provides the necessary barrier coat between the wood and the Tru-Oil, allowing the oil to cure.
    Very Nice.

    Did you do a french polish technique with the Tru-Oil

  8. #8
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    Quote Originally Posted by Steve-atl View Post
    Very Nice.

    Did you do a french polish technique with the Tru-Oil
    I've never heard of anyone using it like shellac. Getting to a good glossy and smooth finish requires quite a few coats that are allowed to dry between coats and level sanded with fine paper (400 or 600) as needed to keep it smooth. This builds some depth. Contrast this with the "wipe on, wipe off" method, which is quick and easy but doesn't build depth or gloss. As the process moves along, you can use 0000 steel wool or fine Scotchbrite to scuff between coats, the goal being to key the surface a little without roughing the surface so much that each coat is a "two steps forward, two steps back" operation. Straight Tru-Oil can be used for the early build coats. To get the later coats to flow out into a smooth and glossy surface, it has to be diluted with mineral spirits. Up to about 50/50 works well. I apply it with a little piece of blue paper towel folded up and held together with masking tape. You could probably use a foam brush but you'd end up spending a pile of money to apply $3 worth of Tru-Oil, without getting a better result. The last coat is flowed on in this way over the entire work piece in a single application and, once you have the knack, it dries glossy without brush marks or need for wet sanding and polishing. At this point, you're done. Obviously, this finish can't be done on the quick. Each coat takes just a few minutes each day (or twice a day if your environment permits) but it's really just a little time spread way out. You get all of that time back, at least as compared with a lacquer finish that must be allowed to cure for perhaps 2 to 3 weeks before wet sanding and buffing.



  9. #9

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    Thanks

    I picked up some Tru-Oil awhile back but have not tried it yet. I am still trying to figure out a good pore fill for Mahogany.

  10. #10
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    Quote Originally Posted by saltytri View Post
    The wet sanding method can result in a very nice surface that is comparable in appearance to a sprayed and buffed finish but without the need to invest in costly equipment.
    What a lovely instrument. Beautiful craftsmanship... What I found in my one time experiment was that it darkened the wood slightly and I lost a little bit of grain in that ziricote. I don't want this sound like it isn't a legitimate technique, and would encourage others to try it.

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