Making an epoxy primer high build

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Nov 18, 2019.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Anyone know if I can add sil cell (32) to paint for a little thicker build and easier sandability?

    Thinking 5%?
     
  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Absolutely not!!!

    It will thicken it.
    It will also dramatically increase how hard it will be to sand.
    It will also dramatically reduce the paint's ability to flow out smoothly.

    Leave paint formulations to the experts. Twenty years ago when I only had ten years of industrial painting experience I often tweaked paint. With the newest variations I don't dare alter paint.
     
    philSweet likes this.
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    How would adding sandable balloons make it harder to sand?

    I just want a 5 mil coating.
     
  4. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Possibly my bad I saw "sil cell" and assumed it was fumed psylica branded. Fumed does increases sanding.

    Other points still valid. Lower flow out of primer will increase brush tracks and roller stipple. Which will require more work to smooth away.

    The balloons are unlikely to disperse evenly.there will be clumps of dry powder left in paint film.

    Micro balloons will clog spray tips / filters. So spraying would be frustrating if at all possible.

    A 5 mil coat is pretty standard. You shouldn't have to doctor the primer to get three. What does the paint can recumend as film thickness? Wet? Dry?

    Do not exceed the manufacturer's recumendation.

    Epoxy primer is not the same as Epoxy resin. It is not nearly as water resistant. Adding powders will further reduce its hydro stabilit, possibly leading to future blistering.

    I consider micro balloons as micro blisters waiting to grow.
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I will sand a test panel tomorrow.

    We added 5% by weight sil32. Stirred well.

    It stipples high and applies difficult to even, but is not intended for a final coat.

    I will soak the test panel in water after sanding to see if any ill effect, but for now; it looks like a good way to get a low build.

    Will report more manyana.
     
  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Well, it failed ftmp.

    The balloons roll up in the paint on sanding, aka corn.

    probably a chance it might work on longer cure time, but it is harder to sand than xtra paint...

    We just dropped our grit back down. Take down some highs and we'll just paint with regular epoxy paint.

    I think paint solids would be better.

    Due to the corning issue; I won't water test.
     
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  7. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry Senior Member

    There’s as much real science in failure as success.
     
    fallguy and BlueBell like this.
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