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Thread: Clear Epoxy to fill cracks / knots - Process?

  1. #1
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    Clear Epoxy to fill cracks / knots - Process?

    Hi all,

    I'm looking into using clear epoxy to fill cracks / voids in a slab table top. I'd like to have the epoxy finish clear. I will be using tung oil to finish the piece.

    I've been doing some internet research and I'm not convinced I understand the procedure.

    1) tung oil in the cracks / knots
    2) epoxy in layers? How thick can you apply epoxy before it becomes a month long drying time or air bubbles can't escape?
    3) sand top like normal
    4) finish with tung oil like usual?

    Are these steps correct?

    Thanks and cheers,

  2. #2
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    Thought this could be a good epoxy. People are certainly using a lot of it in their projects.

    http://a.co/9xRye7w

  3. #3
    1) fill with epoxy first- oil resists glue adhesion

    2)epoxy cures by a catalytic reaction, so curing is not inhibited by depth but is accelerated by it. Because the cure is exothermic, large volumes of epoxy will "kick off" prematurely, producing toxic fumes and a degraded mess. The practical depth limit depends on the ambient temperature and the specific product being used. I attempted a fill with West System 105/205 approximately 1 /3/4" deep x 0-1" wide x 6" long at 65 F and almost succeeded, but at the end of the accelerated cure the mass developed some visible fractures at its core. Had I used a heat sink or a fan or put the piece in a colder space it probably would have worked out.

    3,4) sand/finish as usual.

    Oftentimes the void you want to fill goes right through the work, so you need to be sure the back side is sealed with tape.Another issue is bubbles, whether entrained in the mix or coming out of the wood. You can try to avoid them by heating the wood and epoxy (on small volume fills) to reduce viscosity, heating the fill surface with a heat gun to pop surface bubbles, damming around the void and overfilling or filling prior to surfacing so the bubbles wind up above the finshed surface, or taping over the void and filling from the back side. Some people degas the mix with vacuum. Some formulations like this one

    https://www.epoxyusa.com/No_Blush_ma...oxy_p/me01.htm

    are less prone to bubbling than others.

  4. #4
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    Don't oil before filling with epoxy. Oil inhibits adhesion. Slow curing products will heat less. Bubbles are minimised by careful stirring to avoid incorporating air. Cheers

  5. #5
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    Thanks! I'll give it a go.

  6. #6
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    non blushing means clear, I'm assuming?

    Ah, nevermind. I was looking for photos / info on the product and came across the definition of blushing vs non-blushing.

    https://masepoxies.com/non-blushing-...-marine-epoxy/
    Last edited by andrew whicker; 06-20-2018 at 11:21 AM.

  7. #7
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    Blushing is also known as amine bloom. It's a good idea to avoid epoxies prone to this. I once had to wash an entire day's painting after the weather unexpectedly changed. It was covered in bloom. Some times I can't avoid products that prone to this. Cheers

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