Indeed moisture can play a big role. Moisture and catalyst are no friends either.
I’ve read that VE’s behave best with a lower hg, as in 20hg for example instead of 29hg.
Something that is often discussed regarding the double bag scenarios. first bag simply gets resin through the part, second bag compresses for controlling part consistent thickness. And to avoid boil points which act or are viewed as a false leak.
HOJO has convinced me to go with only absolute pressure gauges as well. More accurate info.More consistent parts.
I am not convinced. Whether it is polyester, vinylester or epoxy, the best results I see with as much vacuum as possible.
2talljohn, did you ever get the problem figured out?
what was the solution?
Noone has thus far mensioned infusion speed… i had the same problem you described, more air bubbles near the surface where the resin was fed from. The further from the feed line, the better the finish until about 1 foot away, no air bubbles at all. It occcured to me that the only thing different is the speed of the flow front… so i controlled the speed of the flow by restricting the resin line at the beginning, problem solved.
30 seconds till clamp off is telling me you are WAY too fast aswell. Slow it down and you will get better results i am sure… and i mean slow it right down to no more than 4 inches of front travel in 5 mins… EDIT:- sorry, i see you a re clamping 30sec after finishing… still, you have the most air where you have most flow media, more flow media = faster - so still, i say slow it down.
The air needs time to escape the front and work its way out to the vac line, if the flow is too fast, the air bubbles get trapped in the viscous laminate and remain there permanently. The air is in solution, in the resin even tho you cant see it. You may also get small amounts of styrene vapour that need to escape aswell.
When I use AOC F010, it fizzes when I catalyze with M50. This doesn’t happen with any other VEs I use, only that particular one. It’s not much of an issue, but I have been advised to use a lower reactivity catalyst.