Is wax alone good enough?

We have been building carbon kayak wing paddles for decades, use PVA and silicone free wax on each and every one of them, good release and easier on moulds, yes its old fashioned but it works and fool proof. Also found that moulds with a VE gel coat and a epoxy resin based laminate tends to stick easily.

I thought I would report back with my test. I made a board and coated it with the same Pro-Form urethane high build primer. I sanded it to 1500 and polished to the same “shine” as my other parts. One section I just waxed, the next was wax and PVA and the third was just PVA.

Thanks to wyowindworks’ tips I set my HVLP at 10psi with a 1.5mm tip. It sprayed much better than before with no “stringies” to been seen. I did two mist coats and then a wet coat with no fish eyeing. The test pieces were about 9"x9" and I brushed on the gelcoat, let it sit until the fingerprint test passed and then put two layers of CSM with polyester ISO resin.

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[li]Just wax - This piece release but it took some effort and was slower to peel away from the plug. The finish was the same low gloss as the part which was to be expected.
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[li]Just PVA - This piece release rather easily. Probably about a third the effort of the just wax piece. The finish was actually better as the PVA gave some gloss to the surface and there was really very little orange peel. Much less than I expected. I should note that the part released from the PVA and left the PVA on the plug so there was nothing to peel off of the part. I didn’t try it yet but I would assume the PVA will peel off the plug easily, if not it will be easy to wash off.
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[li]PVA and wax - This piece release the easiest, probably about a quarter or maybe closer to a fifth of the effort for the just wax piece. The finish was the same as the other PVA piece but for this one the PVA came off with the part leaving nothing on the plug. Of course it peeled off the part quite easily leaving a nice finish with little to no clean up.
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In conclusion I was surprised at how good the PVA finish actually was. If you have a perfectly glossy plug or mold it would degrade it with some minor orange peel but for my case it actually made it better. I will be clearing one part and painting the other one I make so this isn’t really something that concerns me. The wax/PVA combo was by far the easiest to release but I don’t know that the added effort to wax the plug will be worth the “falls off like butter” result. I am tempted to just PVA my parts and save the time.

Hopefully this will help someone else out in the future. I’ve gleaned so much from this forum I’m glad to finally be able to give a small amount back. :slight_smile:

On a side note, I was planning to finish this project last summer so I purchased my gelcoat almost a year ago. I didn’t open it until now and I found it as a solid chunk in the pail. I was able to get enough liquid form at the edges to do my test pieces but the pail is 99% wasted. I wasn’t aware that it had such a short shelf life as I thought it would be like polyester resins which I have used years after purchase. Just a heads up for others like me with little experience that don’t know these things. :frowning:

Thanks for posting your findings. This will certainly help visitors with the same questions. Perhaps a little vindication for PVA here…

The main reason I’m not a fan of the wax and PVA combo is I’ve had some issues with PVA separating when sprayed over wax. It could be that my mist coat wasn’t correct or something but I’ve found just correctly sprayed PVA is good enough anyway.

Sorry to here about your gelcoat. The life span of these products varies – this is always something to consider when planning your projects.

Shoe, I’ve found that the fisheye problem is common when spraying PVA over a freshly waxed surface. A clear coat sprayed in behind the PVA almost always will fisheye it seems. I’ve found that if I use water to wipe down the freshly waxed mold surface and go back with another clean towel I can get rid of this problem. I guess it tones down the wax without stripping it.
I like PVA for quick jobs and find it very useful. I hated it until I started spraying it.