Minimising bubbles in epoxy

After a discussion on another thread about minimising bubbles in epoxy, this turned up in my feed today.

My son-in-law uses a lot of resin in wood-turning and he has both a compression and vacuum setup, but usually we use those by inserting the casting in the pot.

This pot appears to be quite well priced and is great for removing bubbles before pouring.

I’ve done a lot of plywood encapsulation in my boat building days and found that pre-warming the object (ply sheets) minimises out-gassing. Others have noted that heat cautiously applied to a surface will also draw the bubbles out, but it’s best not to heat the resin itself (unless you live in a very cold climate) as that speeds up the curing process.

If you buy one, let me know how you get on! :smiley:


On the first beach sign I made (the one I messed up beyond repair) I had it all finished and was going to do a flood coat of clear epoxy on it. I bought a vacuum pot from vevor and tried using it to pull the bubbles out. The epoxy set up in the pot in literally 2 min. Hard as a rock.

I have no idea what I did wrong lol. Ended up doing another pour and it wound up with so many bubbles in it that I had to surface it off and redo it. That’s where things really went down hill lol. On the second sign I opted to skip the flood coat and just put Rubio on it instead and I’m happy with the outcome.

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When you make a huge pot of epoxy like that the chemical reaction as it cures generates a LOT of heat and that accelerates the cure. As you have seen, when it goes it really goes quickly and can get dangerously hot.

Make smaller batches - cool the resin a bit first, and pour it out over as large an area as you can as fast as you can!


Yes lots of ppl use the vacuum to pull the bubbles and you can also limit the bubbles by not whiping the epoxy just stir it even and slowly.

When I do surf boards I flood it on then use a map gas torch and it instantly takes the bubbles out it was scary doing it at first. But I think it either removes some surface tension and the bubble pops or it is some kind of gas affect. I have tried hot air gun but it wasn’t as good.
And when I mean torch I mean like a quick second flash over. Do not hold in one place.

Some dyes will accelerate the reaction too. And you can get different speed epoxies.
I like the west systems stuff they have a metered pump system that is so cool. Literally one pump a
One pump b
And that’s it it’s All measured. One sec I think I have a video of me doing it. And also seeing some surface tension oddities.
Couldn’t find the one vid but here is me using torch on my arcade top thingy

I was wondering if an aluminum pot sitting in ice water would work for some situations. I wonder if taking a cold evacuated mix and pouring onto a warmer part might bring bubbles into the finish. Maybe the optimal process would be cold vacuum, followed by brief hot vacuum, followed by a pour at thermal equilibrium.

Some of the clearest pours I’ve seen were done with room temp vacuumed poly resins. So I also wonder if resin choice is enough to get great results like that.

Resin choice is huge, for sure. Even just working with technical resins, the ones that are intended for potting components take a day to set, even in large sections, and need to be oven cured to get cycle times down to hours. They can have pot lives of many hours, too. The ones intended for laying up fibreglass or other thin section uses tend to set up in hours in ideal conditions but can have pot lives of 10-15 minutes if you’re not careful.

There are casting and ‘deep pour’ epoxies available specifically for that purpose. The long curing times and long pot times are exactly what’s needed to get that crystal clear finish. They cure cold to avoid overheating and discolouring, they have long pot lives that allow for slower, less aggressive mixing as well as settling times and vacuum degassing times etc.

Edit: Personally, I think anything like an ice water bath might not be the way to go. It’ll help slow the curing down, for sure, but will also slow the mixing and handling down and time is critical. The aluminium pot might be helpful, but I think ultimately it’s more about the sectional thickness. The center of the pot is getting to hundreds of degrees while the outside of a plastic pot is at 50-60 degrees. Having an aluminium pot will bring that outside down to 20-30 degrees, potentially, but the inside of the section will still be a couple hundred degrees higher than that in a thermal runaway.

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I’ve had that exact thermal runaway situation before but with a high frequency transformer that took me a day to build and that needed to be tested/shipped at the end of the week nearly getting trapped inside it. My plan was to mix a bigger batch than we’d normally work with and dip the assembled transformer in it for a while, let it soak in, pull it out, clean off the excess and then end up with a nice vibration-tolerant transformer.
After it was in there for a minute or two, I noticed a weird smell, felt the heat radiating off the jug it was in and then had to heave it out of the extremely hot and mostly set epoxy by the leads. Thankfully, I think the thermal mass of the transformer core/coil meant that the epoxy stayed cool where it was in contact with the transformer and so it came out leaving a perfect impression of where it had been. We then had to figure out how to scoop up the remaining chunk and charge off through a fire exit with it as it was heating, cracking, changing colour and starting to really, really stink. Good times. Maybe not good. Definitely times.