white patches and epoxy bubles corrected


Hello. This is a repeat message. Hopefully the link will work now. I put several photos of the white marks, as well as the epoxy bubble marks, on my kayak.

See my previous message, about what happened. My two questions:

A) should I sand these marks? Should I do light hand sanding, or should I use a machine and do serious sanding?

B) would it be advisable to apply another coat of epoxy over the top, to cover the fiberglass weave still visible?

Thanks for any comments.

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RE: white patches and epoxy bubles corrected


First, here's the picture so we can look at it while we're talking (click on it to enlarge):

So the white areas are definitely poorly wet-out cloth. Some of them look to be just a few threads that  didn't get enough epoxy, others look to be patches that got lifted up and away from their epoxy by outgassing. Alternatively, the patches could also have been caused by contamination on the cloth that prevented it from absorbing the epoxy.

The occasional white threads are a purely cosmetic problem. They'll make a varnished finish look sort of rough, but they won't affect the performance, strength or longevity of your boat. Those you can ignore. They'll be taken care of when you fill the weave. If you paint the boat, no one will ever know they existed.

The patches with bubbles behind them need to be taken care of. Over the boat's lifetime, micro-cracks will form and water will eventually get under the glass. Thermal cycling will lift the glass away and in the meantime the water will be rotting the wood. If you want to keep and use the boat for more than a couple of years, you have to fix them.

If you want to have a nice varnished deck, I'd say take off the glass and try again.

If you're going for a painted deck, you can just remove the white patches. If there's a bubble behind a patch, an exacto knife or fresh razor blade lets you peel it off. Alternatively, a dremel will let you grind it away. However you do it, once you've removed it, clean up the area with some sandpaper and paint it with epoxy. Then just fill the rest of the weave, fair it and paint it. The vast majority of the deck will be glassed and the few spots you've had to repair will be invisible and will not affect the boat.

Good luck,



RE: white patches and epoxy bubles corrected

Thanks for your comments Laszlo. You explain things well.

When you write "take the glass off", you mean get a sander, and sand the fiberglass and epoxy off, and go down to the wood?

And when you write "a dremel will let you grind it away", a dremel is some kind of rotating drill?

But thank you. You've helped my head get an understanding of what is going on. Dave.



RE: white patches and epoxy bubles corrected

Hi Dave,

To remove the glass you can either sand it off or heat it with a heat gun and peel it off. The heat softens the epoxy so the glass can be peel (use pliers). Once it's peeled, let everything cool down and harden up again and sand the surface smooth with #220 paper.

Yes, a Dremel is an electric rotary hand tool with interchangeable cutting, grinding and drilling bits. There are many different versions with a ridiculously huge assortment of bits. This is currently their simplest one, the 100 series, in the $40 range:


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