Gelcoat applied, no catalyst used

[D.D.]

Friend painted his anchor locker with gelcoat and did not add any catalyst. Has been "drying" for three weeks and is not hardened. He called Sabre, who shipped the gel coat with no catalyst, and was gven the option: remove with acetone and apply again. However, can a second batch mixed with the catalyst be applied directly over what's altready there and curing take place? To remove with acetone will be a very difficult job, but will the above solution work? ANY input will be greatly appreciated.

[fgd3]

I've had success getting polyester resin to cure by mixing another batch with extra catalyst and topcoating the uncured resin. It's a bit tricky to get the topcoat applied before it becomes unworkable. Mix batches small enough that you can apply them in the limited pot life.

Fabbian

[brankin]

Your friend is probably out of luck having waited this long because the reactive monomer styrene has evaporated well below the level designed by the manufacturer to react and cure the gelcoat. Trying to put new gelcoat on over this layer will work but could lead to unintended consequences such as alligatoring.

The best bet is to wipe it all off and reapply a fresh coat and make sure it is the waxed version of gelcoat. Good luck.

[sabray]

He could try a small spot with just pure polyester resin. Mix a very small batch and try it on a spot maybe 6x6"

[minaret]

I used to run the gelcoat spray booth at a major production facility, and having done this before I can tell you there is no fix other than a 5 gallon bucket of acetone and a bundle of rags. Be very thorough and make sure all of the uncured gelcoat is removed, it will never cure and any gelcoat you put over it that does cure will almost certainly alligate. I've seen people go to great lengths to try to solve this, inlcuding spraying straight catalyst on the uncured gelcoat within an hour after it was sprayed. Nothing works, you're not gonna get catalyst down to the gelcoat that is actually touching the substrate, which is the part that matters. Worst case scenario, you overcoat it with catalyzed gelcoat, which cures nicely with no alligation. The uncured stuff will still be trapped under it, and eventually it will all let go, clogging your limber holes with gelcoat chips. Nope, there's no easy way out of that one. When you bust out the fiver of acetone, be careful of ignition sources, that much acetone fume is dangerous stuff! I'm still laughing at the guy in the yard who tried to provide ventilation for acetone fumes during a wipedown of his bilge with a shopvac. The shopvac was sitting under his open forehatch, and when it exploded the lid shot out of the hatch about fifty feet in the air! Even fans will provide ignition, be careful.
Oh, and make sure you use surface seal in the last coat for proper curing. If your buddy didn't know to catalyze gel, I'm guessing he's not familiar with waxing it either.