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Thread: Pin holes in epoxy??

  1. #1
    Join Date
    Sep 2017
    Milwaukee WI

    Pin holes in epoxy??


    I’m filling cracks and voids in live edge slabs with west systems epoxy. For the long thin cracks in particular, I seem to keep getting pin hole gaps along the way and it looks pretty bad. I’ve also realized you can’t just fill them with more epoxy, as the cracks mysteriously don’t get filled!

    I’ve tried to be diligent about using a torch to pop air bubbles as the epoxy is curing, but admittedly I don’t babysit the piece.


    Any technique suggestions to avoid this? And now that I have these holes, how do I get rid of them?

    Many thanks,
    Last edited by BrianD King; 02-08-2018 at 6:54 PM.

  2. #2
    You may want to look at a different formulation for this use. I have used West 105/205 for years with the same issues. Lately I have been using this product with fewer bubbles, and there are many casting resins out there which are no doubt designed with that in mind. Heating the substrate and the resin mix prior to application can help avoid bubbles coming from the wood interior and decrease the viscosity of the fill, allowing entrained bubbles to rise to the surface more easily. Take care, though, with overheating the epoxy as the fumes are not healthy. Some have found success putting the mixed epoxy in a vacuum pot.

    The one thing that has helped me the most is to fill the holes when the lumber is still rough. The bubbles that rise to the surface can then be planed off in the milling process.

  3. #3
    Join Date
    Apr 2016
    Take extra care when mixing. The air is incorporated at this stage. Generally mix slowly using a stirring action rather than a beating action. It can be a problem with many epoxy products. Our guys are trained to avoid the problem. Cheers
    To break the rules, you must first master the rules.

  4. #4
    It's important to figure out whether your bubbles are from mixing or from voids where you pour over a narrow gap...

    For the first problem - I know several fellows who use a small hand held vacuum pump to pull all the bubbles out of mixed epoxy before the pour.

    For the second problem.... Use slow slow set epoxy. Warm the epoxy to lukewarm - it will thin considerably... Pour from one end and let it flow down into the bottom of the crack and fill bottom to top. Use toothpicks or wooden shish kebab skewers to work out all the bubbles as you go... You will be surprised how many bubbles come out and how much more epoxy you will have to keep adding... If you can work out a dome that seals for a vacuum pump - use it to work out remaining bubbles... It will feel endless - but you will get them all....


  5. #5
    I had similar problems recently. I recoated using a small glue syringe with mixed results. It took a few applications. I also tried using wood epox on one area as a test which worked better for the small holes. I will use wood epox in the future. It is made by Abatron. We use it for exterior repairs mostly.

  6. #6
    Join Date
    Apr 2013
    Kansas City
    For fixing these holes, how about filling with CA glue? They look pretty small and shallow.

  7. #7
    Join Date
    Apr 2009
    Amherst, NH
    If the crack doesn't go all the way through to the back side of the slab, you can carefully drill a hole from the front side to the back side to give access to a syringe. Then tape over the show side, flip the slab and inject the epoxy through your hole into the void. Leave the slab upside down while it cures. The bubbles rise slowly while the epoxy cures so when you peel off the tape your show side is bubble free.

    Of course, I'm afraid it might too late for that for your project.


  8. #8
    Join Date
    Jan 2008
    1.5 hrs north of San Francisco, CA
    Another possibility I didn't see mentioned is air entrained in the wood (or trapped in cavities) expanding as the wood warms (due to rising temperatures during the day, or epoxy's exothermic reaction) and "blowing bubbles" in the epoxy.

    This is a significant problem when varnishing floors in the morning with rising temperatures, and getting hundreds of tiny pips in the finish due to the bubbles. I expect the same could occur for epoxy. The solution for varnish is apply finish later in the day when temperatures are falling. I don't know how hard it is to overcome the natural heating from the epoxy itself.

  9. #9
    Yes, epoxy is best applied as temps are dropping. By far the best method for me has been to warm the resin and hardener considerably before mixing. Makes a huge difference with the air bubbles. For the little missed areas like in your pic, I usually use CA glue with the instant set spray. If you use some kind of non-clear filler, it will stand out like a sore thumb. CA matches epoxy well.

  10. #10
    In my experience, it happens most when the voids are big. For this reason, I like to do these in stages.

    For the first coat, fill per normal, but level it off with a scraper that is flexible and creates a slight concave hollow.

    Next day, fill it again time making it proud of the hole and letting it dry before leveling finally.

    On big voids I always dye with black because it makes the epoxy opaque. If I donít, I can sometimes see imperfections. Also, sometimes bubbles dry IN the epoxy on thick fills which means the product can appear opaque or phlegmy yellow even after dry. Dyeing with even a single drop of Transtint eliminates this threat.

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