Epoxy takes days to cure when very cold

[tronic72]

Hi,

I filled a heap of holes yesterday and came back today to find the holes in varying degrees of hardness (or softness). This was the second time this happened so I began to investigate via the “interwebs”. First I suspected the ratio was wrong but I am pretty pedantic with this and stuffing up the ratio once was plausible but twice seemed unlikely.

Next I looked into the “fillers” which I was given by a colleague because I left mine at the house but upon asking him he said the fillers (used to lightly thicken the epoxy) were fine as he’s used them weeks prior.

I then noticed that the epoxy outside was less hard then that in the cabin and this got me thinking that maybe there was an issue with the temperature. So I called the manufacturer and they advised that providing I stirred it long enough and got the ratios right it would eventually go off.

Finally (and I should have looked at this first), when I mix epoxy I always do so on a square or cardboard taped to a piece of ply. I do this so I can see when and if the product has cured. Id forgotten this piece of ply was in the bilge and as per the manufacturers advice the thin residue of epoxy has in fact cured.

Moral of the story for other members to learn from this; during cold temps epoxy can take days to cure, but given time and heat if possible will eventually set up.

Hope this proves useful and stops others having to unnecessarily remove epoxy (like I did) that may just have needed more time.

Cheers.

[Jammer]

..nod... Nothing worse than getting some uncured epoxy on the doorknob in your garage in the middle of winter when you're using heat lamps to get it to cure on your boat. Stays sticky until spring.


On the flip side a 120° oven will work wonders for smaller parts.

[Spot]

I have used incandescent 'heat lamps' to warm small epoxy projects to that 100-ish F 40-ish C temp to promote curing. Keep checking the setup distance so the epoxy and/or surrounding material does not get too hot. This has worked for me on sub-freezing concrete in my garage where I dump my extra epoxy into the deeper pock marks to bring them back to floor level. One repair was on the lip of the concrete under the overhead garage door and is still holding tight after a decade.

[Rumrace]

It’s not cold enough in Tuktyuktuk to mess up Epoxy. It’s a bad mix. Epoxy gets so hot curing it burns moulds. 50 F is too cold for Epoxy but bagged it’s like 220C

[capt jgw]

Epoxy sets by a thermal reaction. The cooler the ambient temperature the slower the reaction. Also the thinner it's spread out the more the heat will dissipate and the slower the set. We can use this to advantage like mixing a large batch and putting it into a roller tray instead of leaving it in the pot. In temps maybe down to freezing, it will eventually set but it takes a long time. On occasion I've mixed too much and put the excess in the freezer to use later. Next day it's ok, but a week later it's set up hard. Also the mechanical properties might not be as good if it sets up too slow or too fast. On critical items temperature is important. Many epoxy formulations come with different "speed" hardeners. Use the one appropriate to your environment of the day even if it means stocking two or three different types.

[hlev00]

I used to mix on cardboard all the time but I was advised by someone with more experience than me not to as the cardboard will absorb resin or hardener to varying degrees and so possibly throwing off the ratios. This would especially be a problem if you apply the resin to one spot, the hardener to another, and then mix. But I have also thought that the degree to which the ratios would be off would depend on the total amount being mixed.

So whether really an issue or not I only use cardboard as a last resort and for something non-critical. I mix in either a plastic cup or on a piece of plastic for small amounts. The hardened epoxy always pops off the plastic so I can reuse it.

Maybe overkill but the last thing I need is one more variable to worry about.

Harry

[capt jgw]

For premixed putties and fairing compounds where both the A and B parts are thick, cardboard is probably fine. We use it cause those putties are really hard to mix in a pot. One thing that might work better though are thin plastic kitchen cutting mats. I get them in packs of three from the dollar store. ($1.25 now). I also use them for laminating small parts that I want a smooth surface on, comes out like glass.

[tronic72]

“Stays sticky until spring.”

[tronic72]

It’s Day three and it all finally went hard. Glad I waited and didn’t remove it all again. ��

[Spot]

Originally Posted by tronic72

It’s Day three and it all finally went hard. Glad I waited and didn’t remove it all again. ��

Nice. I thought read somewhere that 10 degrees F /5 degrees C is a factor of 2 for cure times. So it the epoxy was designed for lab temp 77F / 25 C then 67 F 20 C will take 2x as long and 87 F 30C would be 2x as fast.

[tilostahl]

[QUOTE=Jammer;3653369]..nod... Nothing worse than getting some uncured epoxy on the doorknob in your garage in the middle of winter when you're using heat lamps to get it to cure on your boat. Stays sticky until spring.


Uncured epoxy will come off cleanly with regular old white vinegar. For some reason it doesn't say that in the instructions.

[Martkimwat]

Originally Posted by capt jgw

For premixed putties and fairing compounds where both the A and B parts are thick, cardboard is probably fine. We use it cause those putties are really hard to mix in a pot. One thing that might work better though are thin plastic kitchen cutting mats. I get them in packs of three from the dollar store. ($1.25 now). I also use them for laminating small parts that I want a smooth surface on, comes out like glass.

I use a block pad of thin plastic sheets that you tear off once used, to expose a fresh surface, it's about 12" x 12" and I guess there's about 100 sheets on the block. It's great for small batches of GRP filler as well, in fact I bought it in a car repair shop here in UK. I'm sure they must be available in the US.

[Boatyarddog]

Originally Posted by tronic72

Hi,

I filled a heap of holes yesterday and came back today to find the holes in varying degrees of hardness (or softness). This was the second time this happened so I began to investigate via the “interwebs”. First I suspected the ratio was wrong but I am pretty pedantic with this and stuffing up the ratio once was plausible but twice seemed unlikely.

Next I looked into the “fillers” which I was given by a colleague because I left mine at the house but upon asking him he said the fillers (used to lightly thicken the epoxy) were fine as he’s used them weeks prior.

I then noticed that the epoxy outside was less hard then that in the cabin and this got me thinking that maybe there was an issue with the temperature. So I called the manufacturer and they advised that providing I stirred it long enough and got the ratios right it would eventually go off.

Finally (and I should have looked at this first), when I mix epoxy I always do so on a square or cardboard taped to a piece of ply. I do this so I can see when and if the product has cured. Id forgotten this piece of ply was in the bilge and as per the manufacturers advice the thin residue of epoxy has in fact cured.

Moral of the story for other members to learn from this; during cold temps epoxy can take days to cure, but given time and heat if possible will eventually set up.

Hope this proves useful and stops others having to unnecessarily remove epoxy (like I did) that may just have needed more time.

Cheers.

Use a heat lamp, variable distances from the work.
Low power, even a light bulb near the work does the trick.
Epoxies make their own heat thru chemical reactions.
Adding a little goes a long way to quicker cure times.
Boatyarddog

[Spot]

Originally Posted by tilostahl

Uncured epoxy will come off cleanly with regular old white vinegar. For some reason it doesn't say that in the instructions.

Double nod...Isopropyl (rubbing) alcohol and citrus soaps will also clean epoxy up before it sets/cures. Acetone is not preferred, it is said to break down the epoxy to a point where it is readily absorbed into the skin thus aggravating any exposure or allergy risks.

[Boatyarddog]

Originally Posted by Spot

Double nod...Isopropyl (rubbing) alcohol and citrus soaps will also clean epoxy up before it sets/cures. Acetone is not preferred, it is said to break down the epoxy to a point where it is readily absorbed into the skin thus aggravating any exposure or allergy risks.

Should ask the question WHY chemically resistant gloves are not being used working with Acetone Or Epoxy.
Just looking for trouble and reactions to the stuff.
West systems has some different hardeners as well.
Don't touch the stuff much, and remove it from skin.
Another trick is Vaseline rubbed on hands if not using gloves.
It creates a barrier that keeps the epoxy away from skin, and comes off easier.
Boatyarddog