Gel coat hardening in cold weather

[dlogvine]

I wonder if I can get gelcoat to harden in 60F. Otherwise will have to wait till it gets warmer

 

[Scott Danforth]

may need a bit more MEKP and it will take a long time to cure, however...... From the following:
https://blog-fgci.com/2016/12/09/tech-question-can-i-gelcoat-or-epoxy-in-the-cold/

Gelcoat has the same magic number; 50 degrees. Anything below 50 degrees and the gelcoat will not cure. The farther away you get from 70 degrees, the longer it takes to cure; meaning at 55 degrees, you could be looking at days before it gets hard.

So, what do you do? The only answer is you need to add heat. Everyone has tips and tricks they’ve picked up on how to work through the cold. Our techs recommend setting the epoxy in a bucket of warm water for a half hour. We also sell drum and pail heaters that will keep your material warm. For small spaces, you will want to apply heat through a heat gun as well. I’ve also seen pool and boat manufacturers put a heater behind the plug to ensure the part is toasty warm before working.

 

[mickyryan]

tent it and use a heater, if possible if not wait it out slimy gelcoat sucks

 

[dlogvine]

The forecast says it will be around 65F by the end of the week. With sun directly shining on the surface it might be warm enough to get the gelcoat harden

 

[harringtondav]

The top coat will not harden at 90F if you don't use a surfacing wax additive or other product mentioned here on the forum. Besides heat, the surface must be protected from air or it won't harden.

 

[Chris1956]

If you are working on the cockpit of the boat, you can toss a couple of blankets over the gunwales and put a small electric heater in the cockpit. Obviously isolate the heater enough to keep it from catching the blankets on fire.

 

[dlogvine]

The top coat will not harden at 90F if you don't use a surfacing wax additive or other product mentioned here on the forum. Besides heat, the surface must be protected from air or it won't harden.

I have two types of gelcoat, one with wax, the other without. I thought that tha one without wax could be used for multiple layers of gelcoat below the top surface, while the gelcoat with wax is used only on the top surface layer. And what hardens the gelcoat is the hardener in the mix.
None of the online resources I read or watched mention necessity of wax in hardening process. Correct me if I'm wrong.

 

[harringtondav]

Your description of the process is correct as far as I know. No wax is fine for building up the thickness in multiple layers. But the surface remains tacky, even after curing. Near impossible to sand and finish. So wax is required to get a hard, non tacky surface for sanding the finish coat.

My one experience was patching the aftermath of a loosing encounter with a channel marker. It was all exterior, high gloss work. The link below is excellent, and part of newbie research. HVLP will give you the best finish vs. painting or rolling. It will still orange peel, but will sand and finish easier vs brush marks. If you go this route, be ruthless cleaning your spray gun. Have a cleaning station ready with a large coffee can and lots of acetone. I thought I could get by filling the cup with acetone and spraying it clear. ..Nearly ruined the gun. You have to remove the fan ring, nozzle, pull back the needle and brush clean everything ...quickly. Don't use the filter under the cup.

I used surfacing wax with each coat, then sanded to keep a level surface. But that was deep patch work. Over coating a decent surface may do with a non waxed coat, followed by a waxed coat.

https://www.bertram31.com/proj/tips/re-gelcoating.htm