Surface Finish on 10oz cloth with epoxy

Discussion in 'Materials' started by ChetMiller, Feb 6, 2023.

  1. ChetMiller
    Joined: Feb 2023
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    ChetMiller New Member

    Hello,

    I am building a piece of furniture and I am looking to achieve a consistent appearance of fiber cloth underneath a thin layer of epoxy mixed with a black pigment. I have built the piece but am struggling to get a consistent/even surface because every time I sand I run into high spots in the fabric, leaving very spotty surface. I am looking to achieve a matte surface finish with visible fiber weave underneath, a much more subtle carbon fiber vibe.

    I have found people getting nice results using peel ply which I will try.
    I am also looking for any tips to mask off the fiber cloth trimmed edges so they don't start pull and get messy during layups, I am thinking of folding black masking tape over them and letting that stay in the layup.

    Any and all ideas are welcome, thanks
     

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  2. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    With 20 years as an individual painter often doing furniture.
    I have NEVER seen a toned clearcoat successfully deglossed with sandpaper.

    My solution
    Build a new piece without adding black pigment.
    Sand to your desired level of fairness and smoothness.
    Spray with low sheen black pigmented lacquer.
    DO NOT SAND THE BLACK LACQUER.

    If you are married to this piece

    Sand to your level of fairness and smoothness.
    Airbrush black lacquer on to the white spots.
    Give it one full coat of lacquer.

    Pealply will leave a rough texture.

    Good luck
     
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  3. fallguy
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    fallguy Senior Member

    In order to not hit the glass; you need to neat coat with epoxy, about 2 oz moxed resin per yard, applied with 1/8" roller. The neat coats also would help close in fabric cutoffs which are razor trimmed carefully to not lift.

    Neat coats are generally applied within the primary bond window to avoid the need to sand and hit the glass..however, some minor sanding is fine and after 2-3 coats of epoxy; you ought to be able to sand for the final coat of finishes
     
  4. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    You can't achieve the carbon fiber look by using tinted epoxy, the amount needed to fill the weave will make it opaque and you won't see the fiber anymore. You need to use imitation carbon, wich is black coloured fiberglass fabric (or real carbon) that can be filled with clear resin and sanded smooth. This you then spray with matte laquer to protect the epoxy from UV.
    The surface you apply the glass on needs to be fair, and there is a difference between smooth and fair. Simple sanding to 180 grit will not make it fair, you need to longboard the substrate and use filler if necessary.

    In your place I would sand the existing surface fair using epoxy filler and a guidecoat, then apply a new layer of imitation carbon.
     
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  5. wet feet
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    wet feet Senior Member

    I don't always agree with fallguy,but he is correct about the necessary course of action.You needed to add enough extra coats of clear epoxy to fill the weave and then flatten the surface.At which point you ought to have given the piece a coat or two of clear 2 part lacquer to seal the surface and act as a base coat for a final coat of slightly tinted 2 part lacquer with as much flattening agent added a would give the amount of sheen you require.Looking at the views that have been provided,I'm not sure whether the white areas will show through.Which really means that you need to find a small area to try coating with epoxy to get an idea of the viability of making it pretty.Given the shape of the piece,you may have some orientations of the carbon that won't look very tidy and that is just geometry.You may have to resort to using the services of one of the fellows that wraps cars with vinyl to get a nice appearance,which would be a bit cruel since you have used the real thing.
     
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  6. fallguy
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    fallguy Senior Member

    Peelply is going to be tricky to use. It will leave a matte finish that reflects the fabric pattern, but it will show steps and ridges where you have a 2nd piece, and it will not conform to too much compounding, and anywhere it lifts or doesn't stay down will not share the surface and you'll end up neat coating it all with epoxy to get to more uniformity.

    If you used pigment in the resin; you can pigment the first coat to see if it will hide your sand thru, then switch to clear to give it some depth; then finishes.

    @wet feet ~ this ain't carbon, he wants the glass pattern to show through a bit, but it will vanish on him (mostly); there is only so much he can do; had he not sanded it 10 oz shows a bit thru, but since he sanded to glass; he probably needs one pigmented coat which will hide the weave more, but it is a touche' at this point...if he wanted the glass pattern to show; he could have used a heavier woven like hexcel 17oz that has larger tows. Should add, he can't really lay that up in carbon now either; it'd be really super hard to get the carbon to cooperate unless he sectioned it.

    Blueknarr also is not wrong. If you wanted the texture surface; you have to go to paint and not really touch the part much immediately. I just think he is past fixing it with finish alone. I spent two weeks building a carbon helm covering; it is tricky work to get to nice finishes with resin systems..harder on contours. Spraypaints are nice, but that assumes nice surfaces were prepared..
     
    Last edited: Feb 7, 2023
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  7. rwatson
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    rwatson Senior Member

    Great advice from everyone. Just an afterthought, I have gotten "special" effects by going to a fabric shop, and hunting up attractive patterns in nylon fabric. If you get a stretchy material, it helps a lot getting around compound curves.
    As its is furniture, longevity and strength aren't an issue.
    Surfboard makers and wood strip canoe builders wanting a stunning result use special optically clear epoxy, as the usual boatbuilding epoxies aren't designed to be optically clear.
     
  8. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Chet
    I'm advising a fellow on another board who has a similar problem. He sanded thru the sanding sealer and stain on a table top.

    Think of your project as seeing some grain (weave) thru black stain.

    Just as you wouldn't sand stained wood. You don't sand the black.
     
  9. rxcomposite
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    rxcomposite Senior Member

     
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  10. fallguy
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    fallguy Senior Member

    Good video, but he would never come in below 2kg with all that neatcoating.
     

  11. rxcomposite
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    rxcomposite Senior Member

    This used to be a trade secret but I guess practitioners of the craft have already discovered it.

    We carefully lay the dry cloth on a thin dimpled backing sheet and pour resin into it then use squeege to even it out, We don't use brush so as not to touch the fiber alignment and keep it looking nice and straight. The dimpled plastic is just scraps we saved from the prepreg but the dimples helps separate the backing sheet easily.

    The resin saturated cloth along with the backing plastic is then cut to pattern as desired with a pizza cutter. This way, there are no frayed edges and it looks like it was CNC cut.

    It was then placed in the mold, smoothed out as much as possible. The backing sheet is slowly peeled away. If there is a compound curve, we use a stiffling brush. This is just and ordinary paint brush cut shorter to male it stiff. we can almost always coax the laminate to conform to the curve. We use twill weave fabric so it conforms easily.

    Then we apply peel ply. Peel ply won't conform to compound curves so time to cut and overlap without disturbing the fibers. Sometimes it is easier to overcut and patch. Much easier. Use the stiffling brush or squeege to help the peel ply absorb the excess resin. The peel ply is slightly oversize 1 to 1 1/2 inches. This provides a grip to the adjacent area to make it "drum tight". So no frayed edges, nice smoothed ends. Contrary to popular belief, peel ply will smooth the surface. Sure it has a matte finish but nothing much a slight sanding will help. A nice coat of resin will finish it.

    The methodology is very much similar as if you are working with prepreg.

    If you want to make a nice polished look, refer to the video above.
     
    Last edited: Feb 9, 2023
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