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Hanaldo
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Personally I think solve the problem as to why you are getting pinholes, coatings are just a bandaid fix. But that's not really very helpful. Can you perhaps measure your gelcoat thickness? I'm not sure how sensitive the GC50 is to thickness (Warren?), but I know some gelcoats need to be pretty spot on 25 micron. Perhaps your issue is not thick enough rather than too thick, leading to undercuring of the gelcoat? I sort of doubt that though. How about catalyst, can you rule out catalyst being an issue? How old is it, what level are you catalysing at? Do you get your catalyst from EC or another supplier?
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Warren (Staff)
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Thicker gelcoats will reduce in clarity for sure. Also it looks like the orangy GC50 is pretty old, perhaps some of the styrene has dried out since you last used it?
It is strange you are still getting milkyness with the new material which kind of rules out the old material being at fault due to age so something else is clearly going on here. Maybe thickness, humidity? contamination when spraying? (eg oil and moisture through compressor is a common one)
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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wochi
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I tryed both ways. Making a very thick coat and a very thin coat. I have measured the thickness and it was 0.3mm on the second try. Catalyst is a couple of months old. From a local supplier as EC doesn´t ship this product overseas and had no problems before with it. My last try will be doing a brush aplication so i can rule out moisture on the spray gun. Although it seams very unlikely to be the problem. As for the pinholes i gave up on trying to get them all out. No matter how i hard i try i allways get them. Even demoulding most of the parts seem perfect but if you do a close inspection you seem them and they show up pretty nasty when i´m applying the clear coat. I tryed all. I degass, i pre heat the resin, i make vaccum drop tests, everything i could find i tried. Never had a perfect part with absolutly no pinholes.
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Hanaldo
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Well there's an issue somewhere along the line, as it's certainly possible (and very easy in fact, once everything clicks together) to get 100% perfect pinhole free results from infusion with no coatings. Actually that makes me wonder if perhaps the two issues are linked. It seems unlikely, but it's possible in the wonderfully complex world of composites. Have you tried spraying the GC50 post-mould? I know it's not intended for that function, but you could see if it goes cloudy after simply spraying it or whether it has something to do with your process.
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wochi
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Never tried that as like you said it´s not supposed to work like that. But can give it a shot. At this point i can only see beeing some oil/moisture passing through the filters and going to the gun. I will do a test using a brush to actually rule out if this is the problem. If it´s not I´m out of ideas. What kind of setup do you use with your compressor? As for the problem beeing connected with the pinholes i really doubt. I tested million of different methods and none could make a flawless infusion. But at this point i would be happy with the gel coat working properly as it fixed the pinhole problems and the parts came out perfect (except for the milky thing)
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Hanaldo
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Gelcoat doesn't ACTUALLY fix the pinholes though, they are still there underneath the gelcoat. And quite often, the part comes out of the mould nice and perfect and everyone is happy, but once the part has been in use for awhile or sees some heat cycles or strangely enough just exists for a bit of time, the gelcoat can start to blister away at the pinholes as they are unsupported voids. So down the track, you can end up with a part that is full of pinholes again. This is why I say it's better to fix the actual issue, as there must be one.
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wochi
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the pinholes are barely visible at naked eye so i think they wont be a problem in the future. I´m not talking about massive pinholes. Like i said before they are barely visible. They will only show up when i apply the lacquer
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FLD
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Could this be gas in the GC50? Superfine bubbles might not be visible as bubbles but would make a coating cloudy. Spraying doesn't aerate a coating sufficiently to cause this as it picks up large(ish) droplets. You could try degassing the GC50. (just an idea).
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Dravis
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To be perfectly honest, I think you have an issue with either your resin (too high viscosity) or starving your part of resin .. I've just infused a tank cover (around 0,7 sq mtr, since the mould used up a complete standard Unimould kit ..  ) It does not have a single visible pinhole in the whole of the "usable" area... This was with a microscopic leak that I just could not find, dropped vacuum completely in 5 hours --- but I just kept the pump running .. Yeah ... I know ... should have spent some more hours finding the leak ... or rebagged, but it was a first test of the mould and some new lay-up ideas (for me at least  ) The part came out near perfect, apart from the pattern of the carbon having shifted slightly making my intended stripe of spread tow off center .. I need a better way of making it stay in place when fumbling around with the backing layers and bagging ...
"Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
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wochi
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I appreciatte your help with the infusion but the point here is to try to understand what is wrong (or what i´m doing wrong) with the GC50 Gelcoat. So, i did my last test using brush instead of spraying. Hazy again! You can clearly see the paths left by the brush on top of the part. You can also see in corners (where is difficult to correctly spread the gelcoat) severe milky aspect. Conclusions: - not a problem with moisture in the spray gun - too thick gelcoat make milky/hazy results My problem still persists because i have already tried to spray much less Gelcoat (so thin it didnt even cover the all surface) and still got haze! Less than when i sprayed more gel but still haze I´m out of ideas... How can i spray an even layer of gel and get a full mould coverage? And how can this be recommended for brush application if it´s almost impossible to apply a thin layer without opening fisheyes?
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