white spots in epoxy after sanding

 

I'm building a 17ft Shearwater Kayak and after the second coat of epoxy and sanding the deck and hatch covers I discovered very small white spots remaining in or under the epoxy.  Could it be epoxy dust in the weave?  Wiping the deck with denatured alcohol didn't remove them.   Perhaps they were there earlier and I didn't see them and epoxied over them?  I assume if I leave them as is they will show through the varnish.  If that's so is there a fix?  Thanks in advance for any guidance you may be able to provide.  I've read several posts here that have been very helpful but haven't found one yet addressing this issue.


7 replies:

« Previous Post       List of Posts       Next Post »

RE: white spots in epoxy after sanding

Might be dust or air bubbles. Either way, if they are small nobody but you will ever notice them. My rule of thumb is if it looks good from ten feet away it's okay. I had some white streaks where dust got under the epoxy on the hybrid deck. I painted over them with model railroad weathering paints that were similar color to the cedar. -Wes

RE: white spots in epoxy after sanding

Thanks Wes.  I think I will treat the spots as you suggest.

I've read and re-read "Twofootartist's Random Ramblings" on the construction of your Shearwater and Merganser Kayaks.   Your work is exceptional.  Thanks for the insight and the construction progress reports.  ~ Roger

RE: white spots in epoxy after sanding

you can try to use compressed air to blow it out. if this are air bubbles, that's the only way I found to remove the white dust. I've tried a lot of different things so far. And I fully agree with Wes: If they are small, nobody than you will recognize them :-))

Rudi (aka burningman)

 

RE: white spots in epoxy after sanding

I discovered the same thing (tiny white spots) today after sanding my WD tandem deck for the first time.  Wondering if anyone has come up with further thoughts or solutions since dunhr's post last month

Here's background:  Building in my heated garage which has been kept at pretty constant temp of 62-65 degrees.  Applied 5 thin weave filling coats to deck per CLC tips for builders (i.e., foam roller followed by tipping with foam brush).  Spots are fairly prominent on bow between coaming and hatch, nearly completely absent on rear deck--both of which were done at the same time on all five coats.  Spots are all in sapele, none in okoume.

Ideas re: cause or cure?

Dave

RE: white spots in epoxy after sanding

The white spots are air bubbles caused by outgassing during the epoxy curing stage. Then filled with epoxy dust during the sanding stage. Vacuuming with a shop vac will get some of them out. Compressed air for the others.

RE: white spots in epoxy after sanding

Thanks, jnjclark.  The spots were very tiny and patterned like a grid.  I assume they originated with air that came up through the weave.  I was concerned because they didn't disappear when rubbed with alcohol or even diminish noticeably with compressed air.  But you guys were correct--altho still visible, they are much less so when covered with a skim coat of epoxy.  All has ended well, and I'm now a full fledged member of the "ten foot club." 

Dave

« Previous Post     List of Posts     Next Post »


Please login or register to post a reply.