Tips for perfect epoxy layers?
July 11, 2020 at 5:35 pm #3125
I was wondering if anybody could help us troubleshoot our epoxy layers? We just did the underside of the galley and the interior side of the floor of the teardrop, and are running into one or two (relatively small) issues. Thought some folks with more experience might be able to offer advice.
Question 1. Small bubbles forming in the epoxy – this seems like a common issue. We rolled it on with foam rollers and then lightly tipped with a foam brush as instructed, but it doesn’t seem to solve the issue.
– We are doing this in the upper range of “acceptable” temperature (around 80-85F), and sometimes after we leave the temp in the garage keeps going up. Would it lead to a smoother finish if we apply each coat later in the evening so night temps let it cure more slowly?
– Is it possible that the foam brush we’re using to do the tipping is too saturated with epoxy? Would swapping out for a dry foam brush be better?
– In the manual, it suggests the foam brush for tipping, but in the videos it looks like people often use a chip brush to tip and take out the bubbles – should we try this instead?
– I’ve seen/heard that gently running a blowtorch about 6 inches away from the surface immediately upon finishing takes the bubbles out. Since CLC doesn’t suggest it in their manual, I’m a bit reluctant, but it seems like a fairly consistent recommendation elsewhere. Any thoughts? Has anybody used this trick to get a perfectly smooth final epoxy finish?
Question 2. Sanding evenly – we’re finding that unless we really go gangbusters with the orbital sanders, it’s hard to get that perfectly uniform cloudy white appearance to the post-sanded surface between coats, due to there being some pitting and variation in the height of the prior dried layer. (See photo to show what I mean).
It feels fairly smooth to the touch but not totally, and the sander clearly isn’t quite hitting the parts that are glassy/clear rather than turning cloudy white.
– Is this normal? Is a little variation in the surface prior to the next coat OK?
– Is it possible we’re putting on our epoxy too thin, failing to smooth it out well enough, or that it’s drying unevenly due to the heat we’re working in?
Thanks for taking the time! Any advice is appreciated.
SJuly 12, 2020 at 12:35 pm #3126toolnut53Participant
re: bubbles forming with temperature increase – Charles’ Law states that a gas expands as its temperature increases. Air in the plywood outgasses as the temperature increases, forming bubbles in the overlying, uncured epoxy. So, applying epoxy as temperatures are decreasing will mitigate bubble formation. I’m pretty sure this is randomly mentioned somewhere in the hymnal, but can’t find the page at the moment.July 13, 2020 at 1:33 pm #3130
Thank you for the response!
We had the bubble problem more noticeably with the second layer we applied, actually – I’d thought that having the top layer on already would prevent outgassing?July 13, 2020 at 6:02 pm #3132canadianhoserParticipant
Rising temperatures will also increase the release of gas trapped within the epoxy itself. Think of a cool glass of water, as it warms up, bubbles form on the inside of the glass. It is not gas being released by the glass, but gases being released from the liquid itself.
Get to know your orbital sander well. You do want to make the surface uniformly smooth before varnish. The varnish itself does not build up quickly, so voids will continue to show through the layers. Spot fill any areas of significant spotting. I use razor blades as scrapers to bring down some of the high spots, and it seems to do a faster job than the orbital.July 14, 2020 at 3:34 pm #3135stretchMikeParticipant
Just adding my experiences from a couple of kayaks and the teardrop:
– what the others have said about rising temperatures and bubbles is spot on;
– I have heard of some using hairdryers to help level epoxy: blowtorches seem extreme;
-re levelling between coats of epoxy: you will gradually reduce those low spots with each coat. You do not need to eliminate them all in the first couple of coats – that would remove too much material and possibly damage glass weave.
– but the final epoxy coat needs to be smooth because varnish does not have the body to fill the depressions. As mentioned before spot filling works well here. Going over surface with a bright lamp reveals any remaining depressions;
– a furniture scraper is also a great way of removing excess epoxy like runs;
– I recommend changing sanding pads very frequently- I bought in bulk. Goes much quicker and you will not spend the waxy residue. I also went with multiple grit increments: 80; 120; 180 and 220 on the final coat.
– I also found that allowing a 2 day cure between coats made sanding much easier.
–July 19, 2020 at 3:13 pm #3146
Thanks all for the advice!
We think the problem was from the heat, but not just from outgassing – the heat in our workspace was high enough to cause the epoxy to cure before the slight patterns left by our rollers and tipping brushes had time to settle/flow at all (eg the viscosity of our epoxy was too high due to the heat). We were able to fix the problem by applying each coat either very late at night or very early in the AM, which also helped with the bubbles from outgassing.
Thanks again all for the troubleshooting and feedback! Really appreciated!
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