After sanding I noticed I have a bunch of these tiny pinholes that look like shiny bubbles. They are indented. Not too concerned with getting rid of them they should fill and sand smooth. My concern is adhesion of whatever goes into them since I can't sand the shiny surface not sure if I'll get a bond. My plan was to fair in spots with epoxy/micro balloons then prime with hi build pre kote then finish coats of color . I don't want to see them reappear in the future as whatever they get filled with starts falling out. Any one experience this, should I be concerned?? Any additional measures to take to remedy this? Thanks  all for your help and stay well PP



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RE: Pinholes/bubbles

oI can't see your images... but if they're anything like what I've seen after epoxifying parts on my Waterlust endeavor, you'll be fine.

Trying to sand 100% of a surface, particularly one that's not dead flat, isn't necessary. I've had small drips I'd not noticed when they landed on unsanded but well-cured epoxy that when chiseled off once they'd cured actually took epoxy off from the underlying surface.... Now I wouldn't rely on this experience to avoid sanding entirely, but it's worth taking note of. 

Film strength is one of epoxy's major attributes why it works for our purposes. It'll allow those smallish defects (I wish I could see) to remain covered by subsequent layers.

If you're really concerned though try dark brown ScotchBrite pads after sanding. The abrasive fibers do a better job of getting into those pit-like depressions & you're not removing much epoxy at all, just breaking the surface glaze.



RE: Pinholes/bubbles

This forum is haunted when it comes to posting pics. They were there then disappeared. Well anyway hope these links work

@spclark I tried the scotch brite doesn't get into the holes. 

RE: Pinholes/bubbles

Right, those new links work. I think those may be outgassing bubbles that've popped, leaving craters. They don't look like what I've seen though, maybe some kind of surface contamination the epoxy went on top of?

You doing anything besides a water-dampened wipe off of sanding dust before recoating? Working on bare wood with ambient temps dropping during application & cure? No supplemental localized heat (like heat lamp?) directed at areas that show those craters?


RE: Pinholes/bubbles

   Bare wood application was at 70 and then allowed to drop to 65 and cure. I assumed they were out gassing. Not too concerned with that just what to do about them now. They are barely visible and most on the bottom of the boat. So tiny I assume the primer will fill in . Thanks PP

RE: Pinholes/bubbles

this does not look overly problematic.  it is fairly typcial that you will get some bubbles and in the sanding process, they will get opened up and filled with sanding dust where all of a sudden, they get noticable as the dust makes them appear white.

the trick i use to make them go away before the next coat of epoxy locks them, in is to very liberally wash the surface down with denatured alcohol to clean the dust out of the opened bubbles.   i also use a tootbrush oaked in denatured alcolhol if i need to to scrub the dust out of these divots.   

then just follow-up with you next coat of epoxy.

RE: Pinholes/bubbles

   @ hspira. This is after sanding last coat of unthickened epoxy. Next is fairing and priming for paint. My concern is long term adhesion due to the shinyness. 
Has anyone ever used Liquid Sander Deglosser or trisodium phosphate on epoxy 

it's used on paint to dull the surface for adhesion not sure it's compatible with epoxy? 

RE: Pinholes/bubbles

I've wondered about that too but given the different natures of paint vs. epoxy I'm doubtful any of those products would work. Then there's the risk that they could leave the epoxy surface with something left behind that then inhibits a decent bond.

I'd use (have used) the brown ScotchBrite abrasive pads (described for use on metal) to good effect where I've been disinclined to want to use sandpaper. Does a fine job with little effort to break the surface gloss of cured epoxy. Then vacuum, follow with denatured alcohol (or just plain water) on a clean microfiber cloth.


RE: Pinholes/bubbles

   @spclark. Thanks. I tried with green scotch brite  don't know that brown would be any different but it does not get down in to the hole to scratch the epoxy. That's why I thought of the liquid. But yeah I agree might be risky. 

RE: Pinholes/bubbles

Brown's stiffer (than green I think but I need to find some green to compare to!) I think, and just how big/small are those holes? I find I can push Scotcbrite into places I'd never bother trying w/sandpaper....

RE: Pinholes/bubbles

i see now that you intend to prime and my perspective is the primer would fill the holes...and i think they are so small relative to the good surface area that you will not have a problem with adhesion.   

last boat i painted, i had a lot of little dots of the primer filling these little holes creating a nice smooth paint surface.  no issues with the paint being sturdy.


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