Gelcoat/PVA interation issue?

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#1

So this is kinda a new one for me. I’ve been making molds for a few years now. It almost looks like aligatoring, but it happened almost right after I sprayed the gelcoat. I used the same mix ratios I always do given the temperatures. Only changes are I sprayed the PVA like 2 days before I was able to get the gel coat on. The gelcoat is close to its shelf life but its not like its way past it. It was also very, very humid the day I happened to spray it. It almost seems like the PVA wasn’t 100% cured due to the humidity. When I peeled off the gelcoat the PVA mostly came up with the gelcoat, but certain areas stayed down on the plug. The little wrinkles were in the gelcoat, PVA, and also stayed stuck on the plug. Some acetone on a rag and the material left on the plug almost wiped away. I’m thinking of putting a dehumidifier in my mold room, and maybe an extra layer or two of PVA to prevent the possiblilty of the PVA being under dry and spraying the gelcoat an hour or two later to eliminate possible over drying. The PVA was almost tacky still which is why I’m leaning towards the humidity made it almost under dried. Thats kinda my only guess at the moment.

Any inputs would be appreciated! Last picture is of the gelcoat/plug surface when I peeled up a large section.

IMG_1157 by AJ Hartman, on Flickr
IMG_1156 by AJ Hartman, on Flickr
IMG_1159 by AJ Hartman, on Flickr
IMG_1158 by AJ Hartman, on Flickr

#2

Was the PVA smooth when you sprayed? My first thought was you didn’t let it thoroughly dry prior to applying the gelcoat but you said it was a couple of days old so that pretty much eliminates wet PVA. I guess humidity could cause a problem like this but I’ve never seen it and I’m in South Florida, not exactly known for crisp cool air. :smiley:

I’m drawing a blank for any other explanation.

Something you might consider is to use PV-6. It’s made by Finish Care (the wax people). I buy from Comp 1. It is solvent based, dries quick and it will create a halfway decent gloss finish if you spray it well. Being solvent based, humidity shouldn’t affect it. Also, again, being solvent based, it doesn’t wash off with water but you can blow it off with compressed air or use a solvent wipe.