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Thread: Witness lines

  1. #1

    Default Witness lines

    Hi all, hoping someone can help with my witness lines woe. Prepping for a nitro (rattle can) spray, I've used a shellac with pumice powder and then some Z-poxy. Consequently I've ended up with terrible witness lines on the sides I just can't get rid of. I'm wondering, though, if I make sure everything is sanded flat, will they disappear under my nitro clear coat? Really don't want to sand the sides back to bare wood if I can help it.

  2. #2
    Registered User sunburst's Avatar
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    Default Re: Witness lines

    Quote Originally Posted by chilos View Post
    ...will they disappear under my nitro clear coat?...
    They can, if you do it right. Spray a couple of coats, let dry, sand lightly, spray again. That should do it, but if not, repeat until it does. Don't sand through the lacquer!

  3. #3

    Default Re: Witness lines

    Thanks John. I'll give it a go. Humidity a bit of an issue here right now (Scotland), but looks like it might be dry enough for spraying later in the week.

  4. #4
    Adrian Minarovic
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    Oct 2003
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    Default Re: Witness lines

    Quote Originally Posted by chilos View Post
    Hi all, hoping someone can help with my witness lines woe. Prepping for a nitro (rattle can) spray, I've used a shellac with pumice powder and then some Z-poxy. Consequently I've ended up with terrible witness lines on the sides I just can't get rid of. I'm wondering, though, if I make sure everything is sanded flat, will they disappear under my nitro clear coat? Really don't want to sand the sides back to bare wood if I can help it.
    If I understand your process, you used shellac with pumice as a filler for some porous wood, what was the purpose of Z-poxy then? It is also used as pore filler which is massaged into pores and sanded back to bare surface. If you used thick layer(s) of epoxy as a sealer over that and then sanded through layer(s) in spots you got wittness lines. Properly applied nitro would likely hide that but I would probably sand it to bare wood surface (perhaps that's what you see within the isles of witness lines in your epoxy coat) and use shellac as sealer, that is time proven base under nitro.
    If you have bare spots and epoxy covered spots on your wood the nitro may show differently on those two surfacesdue to varying optical properties of wood and epoxy.
    Adrian

  5. #5

    Default Re: Witness lines

    Hi Adrian, yes, that was the process. I pore-filled with shellac and pumice but had a small ripple in each side that needed something thicker and was too deep to sand out. Bit of a bodge, I know, but it seems to have worked.
    And as it happens, today is a perfect spraying day here - warm with humidity in low-40s, and the first coat of nitro seems to have totally covered the witness lines. Time will tell, of course as it cures, but so far it's looking good and I'm hopeful.
    Anyway, upshot is a time-consuming lesson learned.

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