# Will epoxy harden in 20 degree weather?

Will epoxy harden in 20 degree weather? (outdoors)? I have a livestock tank with a tiny leak. I want to put some JB Weld on it. I have the quick dry stuff (supposed to dry in 5 minutes). It's been in the house so at least the epoxy is warm. Maybe I should put a hair dryer on it ourside?????
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It will eventually harden.
I would go by the usual rule of doubling/halving per 10 degree C temperature change from "usual room temperature" (20 or 25 degrees C).
20 degrees F is roughly 30 degrees C below a fairly normal room temperature. So I would say double that 5 minutes 3 times, to 40 minutes - and that is for it to set.
There is a longer time for the epoxy to reach full strength. I forget now, but I think 5-minute epoxy is supposed to have close to full strength in 2 hours. Double that 3 times, and this is 16 hours.
Epoxy cure times may depend to some extent of heating from curing, and if cool conditions prevent curing fast enough to achieve temperature rise, the curing may be slowed down more. Also, double time per 10 degrees C decrease in temperature is a "1-size-fits-all" kind of a rule.
But the epoxy will fully cure as long as it has been properly mixed.
- Don Klipstein ( snipped-for-privacy@misty.com)
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BobR wrote:

I think that uses one of the epoxy formulations that only cures at any decent pace at elevated temperature, or else the shelf life in a freezer is shorter than years on end.
http://www.gmtcomposites.com/technical_information.htm
The pre-preg here lasts months in a freezer, is good for about a month at room temperature, and it sounds to me from that page that curing is achieved with 250 degrees F for an hour.
This ain't the epoxy you get in a hardware store, and it still does not go forever without hardening in a freezer.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Mar 2, 6:50 pm, snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

The epoxy you get in a hardware store still requires an exothermic reaction to cure. Cold will halt that reaction from occuring. I use a number of different epoxy formulations from 5 minute epoxies to structural adhesives. None of them will cure in freezing temperatures. The key point remains to read the directions for the epoxy being use to determine the appropriate cure temperatures.
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I used JB weld at JB welds recomendations of 20f, it cured, and JB said it would, it just took days. So what you state is wrong.
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ransley wrote:

NO, what I stated is totally accurate. I repeat, NONE of the epoxies that I routinely use will cure at freezing temperatures. I don't use JB Weld since it does not meet my needs in any use. JB Weld is NOT the only epoxy and every epoxy adhesive is formulated differently. Some may cure in cold temperatures, others may not. All require an exothermic reaction to cure and that reaction is dependent on formulation and temperature. Some formulations may be highly reactive and will cure in colder temperatures given adequate time and sufficient amounts. Others will never cure in cold.
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Bob R,
I guess it's all in how you parse your original statements. You actually said a couple of different things, one of which is probably accurate, and one which may not be.
Let's re-cap, in reverse:
re: I use a number of different epoxy formulations from 5 minute epoxies to structural adhesives. None of them will cure in freezing temperatures.
None of us can question the accuracy of that statement, since only you know the types of products you use. I'd be willing to call it 100% accurate, since I trust that you're not lying to us.
re: The epoxy you get in a hardware store still requires an exothermic reaction to cure. Cold will halt that reaction from occuring.
The accuracy of that statement may be questionable. One could take that to mean that *any* epoxy purchased at a hardware store will not cure since "Cold will halt that reaction from occuring". If even one brand of epoxy that will cure at cold temperatures is available in a hardware store, then that statement wouldn't be accurate.
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Not really, cold will halt the reaction but at what level the cold will halt it is the question.
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BobR wrote in part:

It is true that the curing reaction is exothermic - as in heat is produced when epoxy cures.
Generaly, temperature rise from the heat produced only affects the rate at which it cures, not whether or not it cures, especially with hardware store epoxies. If a significant temperature rise caused by the heat from the reaction was actually necessary for the epoxy to cure, then small amounts or thin layers of epoxy on metal objects would not cure.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:

Thin layers of epoxy on metal objects may in fact never fully cure and will never reach the bonding strength expected.
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BobR wrote:

My experience so far with hardware store epoxies is that thin layers on metal objects do reach full strength.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Mar 3, 9:23 pm, snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Not all epoxies are created equal and unless you have tested them to specification you may never really know for sure. I have used a lot of epoxy and have been very happy with the overall performance when used according to the recommendations and specifications of the manufacturer. To give a blanket answer that all epoxies will cure at a given temperature or usage is wrong and should be avoided. The most important thing is to ensure that you are familiar with the capabilities and conditions of use before using any epoxy.
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Sounds to me on that basis like close to average midafternoon midsummer conditions in San Francisco, Seattle, London, or Anchorage Alaska or Fairbanks Alaska.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Sat, 01 Mar 2008 01:10:40 -0600, snipped-for-privacy@invalid.com wrote:

The epoxy may cure, but it will do so MUCH slower and the final properties of the cured epoxy may not be the same as it would be if cured within the recommend temp and humidity range. Yes, humidity makes a difference too.
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replying to Don Klipstein, Chuck wrote: 20 degrees F is roughly 30 degrees C below a fairly normal room temperature.-----that does not make sense. 30C is 86F so you are saying a fairly normal room temp is 106F. I would say that 20F is 9C below a normal room temp of 20C. So do your calculation using the number 10. In your example you use 5 minutes. Double that once for an answer of 10 minutes
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On Saturday, March 11, 2017 at 11:14:05 AM UTC-5, Chuck wrote:

Not that it really matters, because the post you're replying to is 9 years old, but what he said was that 20F is roughly 30 degrees C BELOW normal room temp. That is correct. 30 centigrade degrees is 54 F degree units. 20 + 54 = 74F. Or the other way of looking at it is 20F = -7C, -7C + 30C = 23C = 74F (room temp)
But I wouldn't count on epoxy hardening correctly at 20F period. I'd put a small heater on it until cured.
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On Saturday, March 11, 2017 at 11:26:29 AM UTC-5, trader_4 wrote:

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epoxy-harden-in-20-degree-weather-728513-.htm

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There are hardeners formulated for cold weather, such as West Systems 205, but even that is only speced for "as low as 35Â°F".
As far as using a heater, there is a technique known as post-curing which calls for applying heat after an partial cure at ambient temperature. Applying heat too soon or too fast can cause out-gassing and bubbles in the cured coating.
Lots of info and techniques can be found in this doc:
http://www.westsystem.com/ss/assets/use-guides/ColdTempBondingonlineversion .pdf