Tiny bubbles/dust in epoxy...?

Hey All,

I have glassed my hull and deck, and have put another two coats of epoxy on after the glass. I do notice tiny bubbles or dust that has created blemishes in the epoxy (due to the lack of a dust free work area, I think).

Can I just sand these tiny bumps/blemishes out before I put on a final coat of epoxy?

 And, will the last coat of epoxy be smooth if I get these areas sanded down?

I plan on putting some type of UV varnish coating on at the end whenever everything is all put together, and I just wanted to ask you all if I was on the right track to successful epoxying at this point in my little adventure.

Thanks for the help so far,

Chris F

4 replies:

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RE: Tiny bubbles/dust in epoxy...?

  Morning Chris,

  My first thought is if you are calling them 'tiny' the casual observer wouldn't see them and not to worry.  Sanding between coats of epoxy never hurt anything and it may be called for depending on how long you are between coats so my input will be go for it. You didn't mention how you were applying the epoxy, it could be air bubbles from your technique. Here's my .02...

  Sand lightly

  Wipe down with denatured alcohol and lint free rag

  Mix final epoxy slowly enough as not to introduce air bubbles

  Apply final coat and tip with a foam brush (an extra set of hands will help)

  That's all the advice I can give for air bubbles, if it's dust in there the only remedy is a dust free environment and you need to decide if it bothers you enough to warrant it. I will say I moved my WD inside for the final coats of epoxy for heat and humidity issues and discovered that inside lighting is terrible. If you do it be advised.

  Your final coat of epoxy will be as smooth as the coat under it, don't count on it filling low areas caused by spot sanding and the same applys with the varnish.

  One last thought about your final coat of epoxy, if you can put it on in the evening or when the temperature is falling you will eliminate the possibility of gassing. 

  That's all I have. hope it helps.

RE: Tiny bubbles/dust in epoxy...?

Thanks for the information and advice (can't thank you by name it's blank),

First, I am applying epoxy with a foam roller, and then I tip it with a dry foam brush (new brush each coat).

Second, I am applying epoxy every three hours or so whenever the swab test proves that I can put on another coat. Therefore, I don't sand between layers of epoxy.

Third, I am putting on thin layers of epoxy so I have no drips or runs.

Fourth, I guess I mix my epoxy with too much vigor (bubbles in cup).

Fifth, I did do a seal coat on the hull and deck before appying the glass, and I did have to sand before the glass, because I let the seal coat dry for 24 hours.

Sixth, I plan to sand these tiny bubbles/dust spots before putting on a final coat of epoxy after the hull and deck are joined...I hope that's right?

Sixth and a half, if I sand these tiny bubbles/dust spots down what grit of sand paper should I use? Aluminum oxide? Wet/dry? etc.

Seventh, I'll stop numbering things in this post so it won't be so anoying! LOL!


Chris F

RE: Tiny bubbles/dust in epoxy...?

   Hi Chris,

   I dry sand between coats with 120 and a light touch, just to 'rough it up a little.' If you have bubbles they should open with the sanding and fill w/next coat or they will sand off completely.  You can have gassing after sealing with epoxy. I don't understand how but it does happen, especially with mahogany. I have had gassing through two coats, so don't rule it out. 

  I wish I knew if the issue was air or dust but this should minimize both:

  If you have the working time or an extra set of hands use a brush to apply the epoxy this time. The roller is great but puts a lot of air in the coat especially if you're putting it on thin. A cheap, wide chipping brush works fine but work the bristles between your fingers first to get the loose ones out. Tip with foam and watch behind the tipping, look for air to form or dust to settle. Spend the next few hours babysitting until she's set.

  Before you do all that cover the boat and mist the work area and floor with water, heavy on the floor. Mist your shoes, and clothes too. 

  Apply the last coat in the evening unless this is indoors. 

  I think that's about all us mortals can do, maybe someone can chime in with more insight.

   One more thing for perspective, We were out paddling today and a nice couple stopped to compliment us on the boats. for a long, long time. My boat still isn't finished it has these 'blotches' in the epoxy I didn't see when I put it on indoors. Looks godawful to me and the stern end of Robin's duck has some glue lines in it. These things don't get noticed by the casual eye. We keep hearing words like graceful, warm, grain, amazing and of course beautiful. You are your toughest critic.

  Hope this helps, Bob.

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