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Thread: Filling knot holes with Epoxy... stain first, or after epoxy?

  1. #1
    Join Date
    Jan 2012
    Location
    Austin, TX
    Posts
    106

    Filling knot holes with Epoxy... stain first, or after epoxy?

    I've got some white oak panels I've glued up. There are a few tight knots. I'd like to fill them. I purchased the system 3 something-88 epoxy. It says it dries clear in 24 hours. I'm guessing I need to use it before stain? (I'm using a General Finishes oil base stain).

    Will it leave a glaring white stain free spot on the knot where the epoxy has filled? Should I try to color the epoxy when I mix it up?

  2. #2
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    8,645
    Epoxy first. You're going to sand the cured epoxy down flush to the wood. If you stain the wood first, you'll likely sand through some of the stain.

  3. #3
    IMHO, don't tint the epoxy on oak if the voids are small enough.

    Tinting it black makes it opaque, which is good for deeper voids where some bubbles may be visible, and the clarity of the epoxy can be compromised.

    Clear epoxy will sand and scrape down flat, and actually does not penetrate into the wood *grain* deeply. This means you can stain and topcoat it reasonably well after.

    However, tinted epoxy is another issue on an open-grained wood. In this case, the epoxy seems to get lodged into the pores, so you have to plane or sand down deeper to remove any trace of color. In the case of untinted epoxy, anything in the pores remains clear and largely disappears - certainly under finishing.

    Epoxy dries hard. You'll need to plane or sand it down to get it flat. It is hard to get it perfectly flush without touching the surrounding surface. So, there is a high risk of cutting through any stain.

    So, I would epoxy, level, then stain. If you are staining a dark color and are nervous about the epoxy leaving marks, then you can prep and stain a single coat. This will get color into the wood and seal it. But be prepared that you may need to apply a second coat after you've leveled the epoxy.

  4. #4
    Join Date
    Feb 2018
    Location
    Seattle
    Posts
    59
    I use this epoxy as my general epoxy (T-88).

    Some info on color that may help:

    - It dries clear but with a Amber tint. It is practically invisible under oil based poly (tried MinWax) and varnish (Old Master's external).
    - It sands and planes well. Oil based stain does not stick to it. I never left it long enough to see if it dries on top on epoxy.
    - Brown pigment that System 3 sells is like extreme brown. It's opaque and stands out. I would guess black is similar.
    - one thing that worked for me (kind of) - fill void a touch below surface and then wait 20-30 mins. When it starts to gel, sprinkler sanding dust and lightly press. You can sand it afterwards and it will take stain.

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