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Hi Caden,
Thanks for your post and an interesting problem to 'debug'. Many people who use polyester gelcoats (which the unimould tooling gelcoat is similar to will testify to the frustrating problem that sometimes occurs where if the gelcoat has not cured far enough when you either re-gel or put on your baking resin you can get a reaction where the new resin (or second coat of gel) attacks the first coat causing it to blister or 'orange peel'. I've never had any such problem with the uni-mould system myself but certainly in the uni-mould system my experience is that the gel cures slower than you would expect and the resin cures faster than you would expect. If you waited a 'few hours' before you put the second coat on then my guess is that this delay was not long enough and that the second coat of gelcoat has attacked the first uncured layer causing the blisters.
You don't say how many hours a 'few' hours is but that first application of gel could take 8hrs easily (depending on your catalyst ratio, the ambient temperature and the amount of ventilation you have in the room). If you re-gelled after only 3 or 4 hrs in cool-ish conditions or with little ventilation then I could well imagine this happening.
I guess that you couldn't see any wrinkles after the first application of gel but you could after the second?
Even without hearing any more info I'm 99% sure this is the explaination. The solution is to ensure that any polyester or vinylester gelcoat is cured well into its safe zone (I just made 'safe zone' up but I want to differential between a B-stage that you would take an epoxy too which is quite different because you would never get this type of reaction if you re-gelled epoxy too soon). This 'safe zone' means that it's well cured and feels hard but is nice and green (i.e. fresh with a surface that will still be responsive when the next coat is applied. In the case of polyesters and vinylesters this is around 8-48hrs.
Matt Statham Easy Composites / Carbon Mods - Technical Sales
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