Pin holes in epoxy??

Hi,

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.

Attachment 378666

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

Many thanks,
Brian

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 http://www.epoxyproducts.com/noblush.html 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.

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

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....

Thanks

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.

For fixing these holes, how about filling with CA glue? They look pretty small and shallow.

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.

Nelson

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.

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.

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 don’t, 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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Originally Posted by Kevin Jenness

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 http://www.epoxyproducts.com/noblush.html 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.

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Nice tip Kevin. I've been using Paul's Basic NoBlush for years, and its loads better than West System, mostly because it does not blush. The most important part of using heat to help is not to heat the epoxy, but to heat the wood itself - alot. Use a heat gun and heat the bond area of the wood and this will expand the air in the wood to come out. Then as the wood cools, it does several things - it heats the epoxy right then, thus lowering viscosity allowing it to soak into the wood better, and the best part is that it creates negative pressure in the wood thus sucking in the epoxy, eliminating additional bubble formation. Personally, I would heat the wood, then pour the epoxy in and try to brush it inside its walls, then let cure for a few hours, then mix a new batch to finish pour.

Another tip for you - I made my own vac chamber from an old propane tank. Cut the top off (emptied it, then filled it with water prior to cutting with cuttoff wheel in angle grinder), lapped the steel edge perfectly flat, then made a 1" thick Lexan lid. I milled a 1/4" x 1/4" deep groove in it with circle jig in router (used the center hole for the hose fitting) and ran rubber gasket in bottom of groove. I bought a 3/4" fitting from McMaster Carr to fit my vac hose and screwed it into the center hole. Works every day (I mix a lot of epoxy in my job).
Attachment 379462Attachment 379461

Hey, John,

I'd be interested in how you can heat the wood without heating the epoxy as well. I can't see how it can be done, unless you're talking about heating the wood prior to pouring in the epoxy.

Based on the several others who mentioned air bubble problems with WEST brand (which is what I've been using for years), I'll have to give other brands a try.

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Originally Posted by John Blazy

Nice tip Kevin. I've been using Paul's Basic NoBlush for years, and its loads better than West System, mostly because it does not blush. The most important part of using heat to help is not to heat the epoxy, but to heat the wood itself - alot. Use a heat gun and heat the bond area of the wood and this will expand the air in the wood to come out. Then as the wood cools, it does several things - it heats the epoxy right then, thus lowering viscosity allowing it to soak into the wood better, and the best part is that it creates negative pressure in the wood thus sucking in the epoxy, eliminating additional bubble formation. Personally, I would heat the wood, then pour the epoxy in and try to brush it inside its walls, then let cure for a few hours, then mix a new batch to finish pour.

Another tip for you - I made my own vac chamber from an old propane tank. Cut the top off (emptied it, then filled it with water prior to cutting with cuttoff wheel in angle grinder), lapped the steel edge perfectly flat, then made a 1" thick Lexan lid. I milled a 1/4" x 1/4" deep groove in it with circle jig in router (used the center hole for the hose fitting) and ran rubber gasket in bottom of groove. I bought a 3/4" fitting from McMaster Carr to fit my vac hose and screwed it into the center hole. Works every day (I mix a lot of epoxy in my job).
Attachment 379462Attachment 379461

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Originally Posted by Marty R Schlosser

Hey, John,

I'd be interested in how you can heat the wood without heating the epoxy as well. I can't see how it can be done, unless you're talking about heating the wood prior to pouring in the epoxy.

Based on the several others who mentioned air bubble problems with WEST brand (which is what I've been using for years), I'll have to give other brands a try.

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Use a heat gun, maybe a hair dryer. Doesn't take long just to heat the bond area, but you have to apply the epoxy before it cools off too much