Epoxy temps - CY

I was under the impression that minimum temps of 65 F were required for MAS epoxy. As I am working through the steps on my Chester Yawl, I am seeing language in the manual saying, "let sit for 24 hours at 75 F..." . 

What is the sensitivity level here? Is it realisitic to think  that the epoxy (fillets) will set up properly at 65 F, if given more time?

It is now October in NH. My basement can do 65 F for a while longer but 75 F would require some external heating. I have enough work yet to go on the boat that full completion was going to have to wait until Spring, but was hoping to get some more steps done this month.


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RE: Epoxy temps - CY

   70 to 75 is ideal but 65 is still in the envelope. If you are scarfing planks or doing structural steps you may want to give it an extra day at 65 to be safe.

RE: Epoxy temps - CY

   MAS has a table (https://masepoxies.com/faq/) that shows that compared with 77oF, 68o F takes 50% longer and 59oF twice as long. Below that is 'not recommeded'.

RE: Epoxy temps - CY


Leave it at least until the fillets are too hard to be dented with your thumbnail. For structural joints you may want to wait the same amount of time again.

A heatlamp is a cost-effective way of heating the boat surfaces, and you can keep the epoxy and hardener in a warm room when not in use.

Good luck,


RE: Epoxy temps - CY

   Also, CLC supplies the 'slow' harder with their kits. There is  also a fast hardener for which MAS quotes cure rates down to 41o ! I've used fast for little quick glue-ups at RT, but not for a big procedure like filleting under cold conditions. Has anybody else?

RE: Epoxy temps - CY

just wanted to jump in and add my 2 cents here.

keeping your epoxy warm is pretty key in my book as it really impacts how easy it is to mix.  so i try to always have the epoxy live in a warm place even if i am using it in relatively cold settings (e.g, in the 60s).

i use an inexpensive electric space heater to keep my garage in the 70s during the autumn months.  probably not as efficient as a heat lamp....but it does the trick.

you can also create a nice micro climate around a part by a combination of a heatlamp or just regular incandenscent lightbulb inside a plastic tent.   just make sure not to start a fire....i often use this technique when it gets cold in a way that i don't want to heat the entire garage.

a couple inexpensive thermometers are nice to have around the shop to know where your temperatures are at.  i have two in my shop....one by the epoxy and one by the piece i am working on.

on the regular hardener vs slow hardener...my experience is from a long time ago and i was not particularly happy with my experience so i have focused on temperature management.



RE: Epoxy temps - CY

Thank you all for these helpful posts.


RE: Epoxy temps - CY

Good seeing this thread as I contemplate a’building my Waterlust canoe kit sometime soon. Been prepping garage (insulation, drywall, door gasketing, added a 50k BTU vented, gas-fired garage heater just this week...) as its birthing’ room.

With fall / winter / spring temps here anywhere from 60F to -25F, I have little budget for gas sufficient to keep this space at 60F 24/7. Mostly heater’s intended to maintain closer to 40F, just enough to keep moisture at bay, with frequent boosts to 50-55F for working sessions. The tent+heat lamp trick will come in handy.

That MAS chart shows a medium hardener available too, may look into that further.

RE: Epoxy temps - CY

'Medium' is actually ~ 50:50 of 'slow' and 'fas't (see MAS FAQs), so if you've already invested in a lot of 'slow' hardener, it's economical to get some 'fast' and mix them. I always make up epoxy using a little digital scale: I take a dollop of resin, weigh it and write it down (I just can't trust my memory anymore!), calculate what 50% more of that should weigh, and then dribble in enough hardener to reach that target. Done this way, it's easy to add more than one hardener-  just match target at the end.

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