Talk Composites - The Forum for Advanced Composites

Gelcoat voids

http://www.talkcomposites.com/Topic39736.aspx

By raygun - 1/7/2021 7:20:32 PM

I've got some weird voids in the gelcoat layer of a new mold. Any idea what would cause this? I used two coats of tooling gelcoat, brushed on. The only thing that comes to mind is that I may have put it on too thick, or not waited long enough (or too long) between coats.
What would cause this? All I've come up with is some sort of gas bubbles. The plug was clean and dry.
I'd also appreciate any advice on how to repair this. I'd rather not throw away a 5' x 4' mold. I could sand, fill, sand and polish, but I'm not sure what to fill it with.
Also, before anyone says anything, yes, the surface is crap. The original part has some serious issues. Polishing the plug makes it *worse*. Clearcoat is self destructing, fiberglass print through, blah blah blah.




By mporta71 - 1/8/2021 8:32:48 PM

 
raygun - 1/8/2021 7:23:00 PM
 
Hanaldo - 1/7/2021 11:56:53 PM
Do a quick search for 'gelcoat alligatoring' and read about what it is and what causes it. You're on the right track with may not have waited long enough between coats, but there are potentially other causes too. Very common issue with styrene based gelcoats.

At least it looks like an easy enough spot to repair. Clean it well, then sand the low spots with 80 grit and clean again. Then fill with the same gelcoat you used to make the mould, but you will either need to add wax-in-styrene or cover the repair with flash tape or release film while it cures so that it fully cures. Then sand it flat and polish.

Thank you! I've seen alligatoring mentioned before but didn't give it any thought. The name makes sense now. Thanks for your time.

In other news, the forum doesn't actually notify me of replies. :/

Same issue - no emails - for me too
@Warren is checking into that I think