Thread: Slowing down epoxy in warm temps

I'm not sure of the hardener you're using with your Bote-Cote, but cooling the resin will also dramatically increase it's viscosity, as well as increase it's working time. The cure rate will not slow down, but you can get some more working time. Bote-Coat has a thixotropic agent added which will make the viscosity issue worse if chilled.

Very few epoxies will last long in 37 degree temperatures, unless it's a special extra slow formulation. West System has one and at 37 degrees, you'll have about 35 minutes working time, which is quite good compared to regular and slow formulations, which will kick off in 5 to 15 minutes.

There are things you can add to the hardener to slow the chemical reaction, but these are well beyond the scope of the average user. The best recommendation in these temperatures is to take advantage of cooler temperatures at night or use an extra slow hardener, like the "tropical" stuff they sell. I'm not sure how slow the tropical is, but it's probably a lot slower then the regular slow.

Thanks Par,
Working time is what I meant, not cure rate as I stated. I've tried refrigerating it a little, just to bring the temp down to the mid-high 20's (guesstimate). This does increase the viscosity a little bit, but doesn't create any problems with mixing/applying. Would going even cooler than that cause any problems other than the viscosity?
Cheers,
Chris

you may end up with moisture in the resin from condensation!!.

Contact Boatcraft and buy some tropical hardener, or glass at night when the temp drops down to below 30C.

I am about to start a canoe for a friend and i will be looking to glass in the cool of the morning , or early evening.

Jeff

Viscosity is a huge consideration for fabric wetout and substrate penetration, so chilling the resin isn't the best way to go. Early evening is best when coating over raw wood, as the falling temperatures will not cause a gas off situation. Early morning can be used for previously sealed (coated) applications, where out gassing isn't an issue and rising temperatures can help the cure.

Why not just mix very small quantities so that you can use it all before it goes off?

Small quantities will go off just as fast larger, assuming the larger quantities are spread out in a thin film and not pooled in a cup. In fact, one trick to improve working time is to spread out the epoxy in a very thin sheet, so it can't build up heat from the chemical reaction. It'll still kick off very quickly in near 100 degree temperatures, but it'll kick off much faster if left in a mixing cup, regardless of quantity.

The only good solutions are to lower the ambient temperature of the working environment and/or use a slower hardener. Some improvement will be seen with cooled resin/hardener, but it'll quickly warm in the working environment and viscosity will be troublesome.

Plan A
I managed my last kayak in 40C+ by mixing small quantities & working fast.
(for me anyway)

Plan B
BoteCote do a high temp part B - tropical hardener - if you are willing to spring
for the extra shillings. (I'm not)

Plan C
Wait for the weather to cool down.

HTH
AJ

Originally Posted by PAR

Small quantities will go off just as fast larger.

I wasn't suggesting that it changed the kick time. I was suggesting that a small quantity will be used up in less time.

I have always used BoteCote with non-yellowing hardener and while I have not worked in 37 degree temperatures, mixing small quantities has been my preferred method of avoiding having epoxy go off in the pot.

I leave my goo (Bote Cote) in a warming box which I switch on as a matter of habit when starting work and yesterday I experienced the problem for the first time.

Late in the day I needed to do a fairly big fillet so an eight pump mix was required and I fooled around coating some bits before adding the filler by the time I got it mixed and into a plastic bag to apply it was too hot to hold......hmmm the ambient temp had crept up to about 30C but inside my warmer who knows.

Anyway all I did was sit the container in a bucket of water for a while and the next batch worked fine.

Mike