By Brian_J - 12/14/2017 5:55:42 PM
Hello everyone,
I just made my first molds and attempted my first infusion which failed miserably due to an airleak. I probably should have removed the wet fabric and cleaned the resin from the mold immediately, but I didn’t. Now I have a layer of resin that has attached itself to the mold surface and has cured. For whatever reason, this resin won’t release from the gel coat. Is there a way to remove it? Or am I looking at either sanding it off and repolishing it/ tossing it and rebuilding the entire mold?
The mold was made from fiberglass and polyester resin & polyester gelcoat.
The mold release was multiple coats of Mequires mirror glaze #8 paste wax AND a thorough coating of pva.
The resin system was an epoxy infusion resin from a dealer in the USA.
Learning lots here and I look forward to your collective thoughts!
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By oekmont - 12/15/2017 5:08:43 AM
Epoxy in a polyester mold is definitely not a good idea. Pva can solve the problem, but the application of pva itself is already difficult enough. It isn't easy to get an even, full coverage of the mold surface. Further, the pva film can easily be damaged during the layup process.
In my opinion, pva is only still that common, due to the good old days, when there was no better option. There are still some minor cases, in wich it might be useful. But this usually involves original models, that can't be painted, and wich are of an improper material for mold making.
What you can do now: bathe the mold in warm water, to get the pva's release propertys to it's max, and then carefully try to work from the outside with a plastic sheet (some cut grp for example). Likely there will be a point, where you'll need a metal tool, to get the epoxy off, and likely you will get some chip offs in your gel coat.
What you can do in the future:
-use vinylester tooling gelcoat for polyester molds
-use epoxy tooling systems
-when using polyester molds, you can use some polyester gelcoat for your part. make sure to cover the flanges as well (except the are for the tacky tape)
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