From Tips for Boat Builders - Fiberglassing:

What if I want to varnish my hull? - No need to worry. 4- or 6-ounce fiberglass cloth will be almost perfectly clear and will look fine beneath coats of varnish. Some precautions, though: you'll want to be sure you have the fiberglass cloth completely filled with epoxy, even if it means extra coats. If you sand into the fabric anywhere, that area may show up under the varnish as a foggy spot in the finish. Also give serious thought to the use of a low-viscosity epoxy like MAS Epoxies. Thicker epoxies make it difficult to wet out fiberglass, and the excessive kneading of the clear epoxy will inject zillions of microscopic air bubbles into the epoxy, creating cloudy or milky spots all over your hull that are impossible to get rid of.

The inculded microscopic ari bubbles will migrate and form larger air bubbles and if the expoxy cures too fast they will not escape. Also thicker coats tend to develop bubbles or the bubbles cannot escape fast enough. I would look at lenghing the cure time and using thinner coats.

I'm thinking about usung a heat gen to float the bubbles to the top...anyone have experance with this?

Conner

I would be leary of using a heat gun for either epoxy or varnish, because they would tend to make both set up before they had a chance to smooth out. A very common problem with varnish is that folks tend to sand their boat and then varnish in the heat of the afternoon in the Summer. I've read that the idea temperature to apply varnish is around 70 deg F, which gives the varnish a chance to smooth out into an even finish before it sets up. If you varnish at higher temps, the dryers in the varnish tend to evaporate out quickly and the varnish sets up with streaks, so I assume that using a heat gun will do the same thing.

One thing that will introduce bubbles into epoxy is if, when you squeegee excess resin off your glass, you then scrape the residue on your squeegee back into your pot. The resin that your squeegee picks up is filled with bubbles. Nick suggests taking a paper cup, cutting a vertical slit along one side, and using that to scrape your squeegee clean.

What I would suggest to reduce bubbles is to handle both epoxy and varnish with care before you apply them. Most epoxy needs to be mixed with hardener for around 2 minutes, but that doesn't mean you have to whip the stir stick around like a mixmaster. Likewise, one good trick to get varnish mixed without too many bubbles is to turn the can upside down a few days before application, and then keep rotating it morning and night without shaking it. That way the heavy stuff in the bottom tends to get distributed in the can. Then stir slowly and patiently once you open the can, and then pour what you need carefully into another container for use. I hope that helps.

Nick has a video showing the use of a heat gun to help get rid of epoxy bubbles.  I do not know about varnish.

360 Paper!  I never went beyond 150 and everyone says the boats look great!

More power to you if you have that sort of patience.  I was in way to much a hurry to get the boat on the water.

May not look perfect but paddles great.

Ed

On using a heat gun on epoxy, you're right and I am mistaken. Cheers

Thanks for all the help

Conner

Any ideas on keeping bubbles out of the epoxy while mixing it?