I believe the fast epoxy is the end culprit. I use a medium speed RAKA epoxy. I pour my epoxy on the cloth and gently spread the epoxy around and let it sit for about 5 minutes. Then I squeege the cloth and the epoxy, and in many cases it's foaming a bit. I believe this is because it's forced out through the openings in the glass and I also believe there is micro particles of glass in there as well making it white.

The molucles of air will come to the surface and disapate but in your case, the epoxy is thick and hardning not allowing this to happen. If I dump my sqreeged white epoxy in a cup, it gradually turns clear again. Never quite as good as the fresh batch but the air casuing any foaming goes away or comes to the surface and releases.

I would switch to a slower hardner and I think your problems would be solved. I think what Rob Max said has validity but it's not absolute because I pour and spread my epoxy I don't get the problem yo¨describe.

Experiment on a scrap of plywood - but I think the faster hardner is the culprit. The other advantage of a med or slow hardner is that you can warm up the epoxy making the viscosity thinner allowing the epoxy to pass through the glass more easily which further aids in avoiding the thick foaming problem you describe.