Fiberglass mould finish

Discussion in 'Fiberglass and Composite Boat Building' started by FiveO, Aug 11, 2018.

  1. FiveO
    Joined: Aug 2018
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    FiveO Junior Member

    Hi

    How to archive matte finish to new shiny fiberglass moulds?

    Sanding paper/paste? It leaves marks?
    Sandblasting?
    Chemical? What?
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Moulds or mouldings ?
     
  3. FiveO
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    FiveO Junior Member

    Moulds - Where the final parts are laminated or poured.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Not sure what the right approach may be, but try Googling "matt gelcoat" or "matt release agent", etc
     
  5. ondarvr
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    ondarvr Senior Member

    There are release agents that can give a very nice uniform matt finish, but...

    The finished surface on the part although looking perfect when you remove it from the mold, can be marked easily from any contact with a hard object.
    The textured (matt) surface look can be somewhat fragile, even a fingernail can leave a mark sometimes.

    Sanding the mold surface can yield good results depending on the grit used, you just need to try a couple grits to see what give you the desired look. This mold surface can be tough to keep looking good due to build up in the texture on the surface, so you may need to re-sand it periodically.

    There are other surface textures that may not look as good, but may be a little more durable.
     
  6. FiveO
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    FiveO Junior Member

    I have tried Frekote matt release agent, but I think it's too thin to make real matte surface. It makes glossy surface a bit duller, but not matt.

    Sanding with p800 grit leaves marks when done by hand. I can't use power tools because of the mould shape.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    A matt clear coat after moulding ?
     
  8. FiveO
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    FiveO Junior Member

    Sadly no.
     
  9. ondarvr
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    ondarvr Senior Member

  10. FiveO
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    FiveO Junior Member

    Thanks for the link, but I think I skip the release agent for texturing.

    What are the other surface textures you mentioned earlier?
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Plenty of moulded plastic consumer goods have matt finish, might be a clue there.
     
  12. FiveO
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    FiveO Junior Member

    Yes, but they have metal moulds. They use acid or sandblast.
     

  13. Mr Efficiency
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    Mr Efficiency Senior Member

    and no wax or release agents ? Maybe you need to line the mould with a matt surface that is its own release agent, that the gelcoat will not stick too.
     
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