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Thread: Using a white primer, mistakes learned from

  1. #1
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    Default Using a white primer, mistakes learned from

    I made a mistake but I learned from it. Along the way I think I found a good tip.

    I have been building a kit okoume lapstrake boat. I used a two part epoxy primer. This primer has a lot of soft filler (perhaps talc) that makes it easy to sand. The soft talc made the surface feel very smooth and the white-on-white made it look the same.

    I put the first coats of dark Interlux perfection on the hull and it was pretty good. I also put that on some other parts and the surface on that was MUCH better. It looked sprayed but I had brushed it. I decided to use 400 grit wet-or-dry and sand the hull to see if I could make it as good as the smaller parts. As I did I slightly burned through the dark paint and saw white brush strokes that were in the primer. They were really obvious.

    That accident gave me an idea that might help you. Before the last sanding of your primer, take some ink and dilute it in some water. Take a rag and stain the porous primer surface with the ink/water. Now as you sand the high spots will be easy to see.

    Perhaps you have good reasons for not doing this or maybe it will be a well known trick.

  2. #2
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    Default Re: Using a white primer, mistakes learned from

    An easier way to accomplish the same thing that I learned from a professional painter: just rub the surface with a piece of aluminum foil. It will leave a gray mark on the high points.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

  3. #3
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    Default Re: Using a white primer, mistakes learned from

    Autobody repair guys will hit the primer with a dusting of a darker color, this is known as a "guide coat" for obvious reasons. Some inks will bleed through more than others, painting over Sharpie can be tough.

    I've been following your build on YouTube, nice see some progress.


    I built one of Clint's early versions of the KDI, it will be a fun boat once you're done.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  4. #4
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    Default Re: Using a white primer, mistakes learned from

    By the second coat of primer I am adding the finish color to the primer (if the boat is not white)

  5. #5
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    Default Re: Using a white primer, mistakes learned from

    Quote Originally Posted by stromborg View Post
    Autobody repair guys will hit the primer with a dusting of a darker color, this is known as a "guide coat" for obvious reasons. Some inks will bleed through more than others, painting over Sharpie can be tough.

    I've been following your build on YouTube, nice see some progress.


    I built one of Clint's early versions of the KDI, it will be a fun boat once you're done.
    That is a gorgeous boat! Wonderful!

  6. #6
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    Default Re: Using a white primer, mistakes learned from

    Quote Originally Posted by stromborg View Post
    Autobody repair guys will hit the primer with a dusting of a darker color, this is known as a "guide coat" for obvious reasons. Some inks will bleed through more than others, painting over Sharpie can be tough.

    I've been following your build on YouTube, nice see some progress.


    I built one of Clint's early versions of the KDI, it will be a fun boat once you're done.
    The reefing seems a bit odd, perhaps it's just that the lines on the starboard side is seen through the canvas?

    /Mats

    Diagnosed with autism. Sorry, not much I can do about it.

  7. #7
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    Default Re: Using a white primer, mistakes learned from

    I also employ the contrasting color second primer coat. Really helps see where you are.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  8. #8
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    Default Re: Using a white primer, mistakes learned from

    Quote Originally Posted by mohsart View Post
    The reefing seems a bit odd, perhaps it's just that the lines on the starboard side is seen through the canvas?

    /Mats
    No, what you're seeing is shadows.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  9. #9
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    Default Re: Using a white primer, mistakes learned from

    Epifanes used to sell a white primer undercoat called Epigrond. But now their primer undercoat seems to be grey:



    half and half with the top coat this can be a bit odd:



    This was the top coat:

    Last edited by Andrew Craig-Bennett; 09-04-2021 at 10:32 PM.
    IMAGINES VEL NON FUERINT

  10. #10
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    Default Re: Using a white primer, mistakes learned from

    IMAGINES VEL NON FUERINT

  11. #11
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    Default Re: Using a white primer, mistakes learned from

    Quote Originally Posted by cstevens View Post
    An easier way to accomplish the same thing that I learned from a professional painter: just rub the surface with a piece of aluminum foil. It will leave a gray mark on the high points.
    I tried the aluminum foil on the unsanded primer where the water line is and it worked, thanks.

  12. #12
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    Default Re: Using a white primer, mistakes learned from

    It will be fun. Hope it is before my 72nd birthday (6 months).

  13. #13
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    Default Re: Using a white primer, mistakes learned from

    Here is a shot of the waterline marked with aluminum foil showing the brush marks in the primer.
    It also shows every dust particle but that is what you get for building in a barn.

    It is a screen grab from a video so it is a little blurry. You can see the plastic in the background where I
    attempted to build a dust free paint room, ha!

  14. #14
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    Default Re: Using a white primer, mistakes learned from


  15. #15
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    Default Re: Using a white primer, mistakes learned from

    A reasonably bright light at a grazing angle in a dark space will show you areas of surface irregularity as well.

  16. #16
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    Default Re: Using a white primer, mistakes learned from

    Nothing beats a guide coat to show up pinholes and other imperfections; also shows how much you need to sand to get smooth and fair.

  17. #17
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    Default Re: Using a white primer, mistakes learned from

    I am hoping to kill two birds with one stone on my latest Lightning restoration. The West guys encouraged me to do a barrier coat of epoxy before priming and painting. And I also want to use a guide coat to show me what still needs to be done. The West guys recommend tinting the epoxy to create a very high gloss black finish that will show all the flaws in the surface. They say the epoxy will stabilize the substrate and my paint job will look better and last longer. Once I have sanded out the problems in the guide coat, I will probably do another two coats to ensure my barrier is a good one.

    I did the same thing on my home built Lightning . . . picture attached. Looks to me like Darth Vader's Lightning.DSCN1403.jpg

  18. #18
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    Default Re: Using a white primer, mistakes learned from

    Somewhere I read about putting food dye in your solvent of choice and applying that as a guide coat. Never tried it though.
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  19. #19
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    Default Re: Using a white primer, mistakes learned from

    If you want the best finish use another guide coat on your 2nd last paint coat. Sanding (320-400g) it will show any excess orange peel, missed pinholes, etc so that your finish coat will be as good as you are able to apply it.
    (A tip from an old-time auto painter who looked at my last paint job (which I thought was pretty good) and said "nice job, but......")

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