It sounds like outgassing.

Have your tried to put on a very thin penetration coat of epoxy first. After this has cured then try glassing over the top of that. The idea of a very thin layer of epoxy will seal the wood, so that no outgassing will happen during the glassing stage. After I put on the penetration coat I go back with a squeegee to remove (all) as much of the epoxy as I can. One tip for you is to scrape (cabinet scraper) the hull between each coat. This will eliminate any bubbles, sags, and drips you might have and not leave epoxy dust.

I hate to sand my hull between coats, I always get dust down in a bursted bubble and if you don’t get the dust out when you put on the next coat of epoxy it just does not look quite as good you would like. I call the dust that has been encapsulated with a coat of epoxy “gold flakes”. I think the gold flakes are only noticeable to the builder (luckily).

I am glad to hear that this is on a sample board and not on the boat it self. One thing that might help is warm the hull (sample board) up prior to epoxying. When you are ready to start epoxying remove the heat source and let the hull cool as you epoxy. This will eliminate many of the bubbles; don’t add heat after you start or you will add to the number of bubbles.

Jason Given

: Before I started coating and glassing my kayak, I ran a test sample of
: coating (S&G okoume with System 3 epoxy) just to make sure I understood
: what would happen. I got hundreds of tiny bubbles in my test sample. So I
: tried a few more and I get the same thing. It is like very rough
: sandpaper. I put on light coats, heavy coats, a lot of brushing, just
: enough brushing to spread it, tried foam "brush" tip off, tried
: my wife's hair dryer. Nothing worked. I am building the boat in the
: basement where the temperature is constant 24 hours a day so there is no
: temperature cycling. I don't want to have to sand between each coat but I
: will if i have too.