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Old Gelcoat? - Don't do it!
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Author:  GD_NC [ Mon Jul 16, 2012 6:11 pm ]
Post subject:  Old Gelcoat? - Don't do it!
I dinged up my boat in the surf while on vacation and was patching up a few places over the weekend. I had a bottle of Gelcoat I purchased last fall. It looked a little funny but I thought it would be ok for a little job. D%# what a mess. Got that suff on my boat and it had tiny little specks in it that kept it from going on smooth. Oh well, I figured it would sand out in the end. Hmm, then came the real fun. It would not cure!!!! It just sat there with no reaction??? I checked the instructions and the mix was correct. It was about 80 degrees out so it should have been too fast if anything. Waited another 30 min... Nothing. I finally had to clean it all off with paper towels and acetone. What a mess. Thankfully I was just touching up a few small places not taking on a big job.

Word to the wise - Gelcoat has a 4-6 month shelf life. Throw the old stuff out and go buy a new can.
Author:  srm [ Mon Jul 16, 2012 6:46 pm ]
Post subject:  Re: Old Gelcoat? - Don't do it!
Did you add surfacing agent (wax) to the gelcoat? It will not cure in open air without this.

You are correct though, these chemicals do have a shelf life.

sm
Author:  GD_NC [ Mon Jul 16, 2012 6:55 pm ]
Post subject:  Re: Old Gelcoat? - Don't do it!
srm wrote:
Did you add surfacing agent (wax) to the gelcoat? It will not cure in open air without this.

You are correct though, these chemicals do have a shelf life.

sm


It was the air-dry / no-wax stuff.
Author:  divimon2000 [ Tue Jul 17, 2012 1:25 pm ]
Post subject:  Re: Old Gelcoat? - Don't do it!
Ive had that happen with new gel. Its finiky for sure but it always seems to dry, just not in the time always specified. Maybe my mixing weakness, maybe ratios, but....like I said, mine seems to always dries even if it takes two weeks.
Author:  jonh [ Tue Jul 17, 2012 3:21 pm ]
Post subject:  Re: Old Gelcoat? - Don't do it!
Good tip Garrett - I'd read about shelf life here on the forums but didn't know the consequences or what to look for. I read vinylester etc has the same issue with shelf life too.
Author:  MVD [ Fri Jul 20, 2012 10:16 pm ]
Post subject:  Re: Old Gelcoat? - Don't do it!
Does it still have a limited shelf life if you don't open the container? I've heard that MEK has a shelf life, but I really don't know.
Author:  optikid [ Sat Jul 21, 2012 9:08 am ]
Post subject:  Re: Old Gelcoat? - Don't do it!
If you keep it in the refrigerator it will last for years and keep the color.
Author:  GD_NC [ Sat Jul 21, 2012 9:13 am ]
Post subject:  Re: Old Gelcoat? - Don't do it!
optikid wrote:
If you keep it in the refrigerator it will last for years and keep the color.


Mine was in the fridge. Purchased last September. Not sure what the story was, but the stuff got really lumpy and didn't set up till the next day. From the looks of what was in the cup I'm gald it was not on my boat.
Author:  MBounds [ Sun Jul 22, 2012 5:04 am ]
Post subject:  Re: Old Gelcoat? - Don't do it!
GD - sounds like your batch may have partially self-catalyzed.

1 - buy your gel from suppliers that have good inventory turnover so that the gel you get hasn't been sitting on the shelf for months or years (don't buy that dusty can from West Marine!).

2 - always do a small test batch before you commit to putting it on your boat. Spread it out on a piece of plastic to get the thickness right and see how long it takes to go off. Adjust the catalyst as necessary. Cure time depends on the catalyst amount and the ambient temperature. Thin layers will take longer to cure than a slug of gel at the bottom of a cup. (It's an exothermic reaction, so small surface area means the reaction heat doesn't dissipate, which speeds up the reaction, which creates more heat.)
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