I've used over 500 gals layup Resin since the early 60's in my non-manufacturing fiberglass projects. . I used to buy the resin in 55gal drums. In South Florida it had a limited shelf life that seemed to appear without warning about a year out to fail/gel unused.


Over a dozen years ago I started toying with Carbon Fiber/epoxy builds
The epoxies are nearly double the cost, and I have been buying them in much smaller quantities.
1 & 5 gal's to save money and concerned about the 1-year manufacturer quoted shelf life, Epoxy seems to offer more options and therefore requires even more flavors (viscosity, cure time, use temp, etc) and therefore needs more effective shelf life to eventually consume.

About 8 years ago I had the idea to refrigerate the epoxies until needed to extend shelf life. I dedicated a regular 24 Cu ft refrigerator for the task set to 43F (I am a Mopar guy). I am surprised today to report I am now starting on my 8th year on refrigerated epoxies and can detect no loss of performance.

Although I do few structural critical build-ups, and I have no way to measure mechanical properties of 8-year-old epoxy, it does seem to be money saver. I have for a number of years begun storing all resins/filler/Hardners the same way and am very pleased with the results. I need a bigger refrigerator.

I expect this year to run out of my oldest stored refrigerated epoxy so the "test" will end at 8 years.

Not sure Epoxy manufacturers are excited to share this outcome.

I am now wondering if paint storage might achieve the same success,

Interesting, I live in the northwest and haven’t seen epoxy (west system) degrade like that over time. I am not familiar with the polyester resins out there, they may have different attributes. The amount of rain here (moisture) here is pretty high so we’ve had problems with opened epoxy containers changing color and then not reacting properly after extended storage. I’ll have to try the refrigerator!

I do the same thing with leftover por 15, definitely helps keep me from having to throw leftovers away and buy fresh for each job which might be 3-4 months apart

Epoxies, resins AND paint, including water base base coat, ALL have solvents in them.
basic science. refrigerating solvent products slows the evaporation rate of the solvents making them last longer.

it's a old bodyshop trick to refrigerate catalyzed paint. doing so almost always extends the cure rate allowing you to use it the next day.
most catalysts stop working at around 50*. this also works with almost any 2K product.

So solvents escape thru sealed metal cans?

Apparently, maybe it would help a little more to store the metal containers and whatever containers upside down or the liquid around the lid or opening like wine bottles with the wine around the cork. Gas, fumes, and evaporation is much "thinner" than the liquid inside and has less possibility to permeate out through the smallest of path. Kind of an extra sealant.

I have refrigerated catalyzed paint and had it last quite some time

I do that often on long time storage, but have yet to find if it's worth it, but can't hurt

yes it can. especially one that has been opened and re-sealed. solvent fumes are extremely thin, much smaller than the product it is thinning out. and can escape thru microscopic cracks in the cans and containers that liquid can get thru.
do a test yourself. get access to a GOOD accurate digital scale. take a unopened paint can. weigh it. and record the weight to the 100th of a gram. open it, then reseal it. set it out in the sun for a 3 or 4 months. i guarantee it will weigh less.
heck even rattle can spray bombs loose pressure even though they have never been used. who hasn't picked up a can that worked perfectly fine 6 months ago that doesn't work now? or better yet a new never used one that doesn't spray 2 years after you bought it. why did that happen because it was supposed to be self sealing after releasing the trigger. and yet there isn't any pressure in the can anymore. where did this pressure go?

and YES storing solvent based products upside down will extensively reduce solvent escape. it still won't eliminate it though.

However, one potential flaw IMO with the can in the sun test, the heated solvent builds considerable pressure that a typical paint can is not intended to contain, the pressure distorts the lid, which might be the main cause of the loss of solvents./weight.

You realize it's just an illustrative example right?

Change it up, put 2 cans in a cabinet, one upside down and measure both.

No, no mention was conveyed it was illustrative, it was shared as a real world test example of an argued expected result.
I did not contest result, I contest the test itself.

does this include refrigerating bondo and it's catalyst ?

Yes, but I have no definitive results to indicate it also has extends life by storing at reduced temps, and since buying it in quantity has little reward, as I only buy what is needed for the project at hand, unlike epoxy purchases. My guess however, it adds shelf life.

A number of years ago while working at an air bag inflator manufacturing facility, I went through training for the leak detection systems in use. The inflators were gas filled to about 7,500 PSI. The gas charge included helium to serve as the detection element for leaks. What I learned in the training was that EVERYTHING leaks. Including multi inch thick glass. The only thing that changes is the leak rate. And as noted above with the atom / particle size compared to the porosity of the container. And note, there is no such thing as zero porosity. It was a perspective light bulb for me when I learned this.

I'm no chemist, but I recall POR-15 used to claim their paint was "cured" by moisture. If that's true, then putting it in a refrigerator would slow the curing process due to the lower humidity rather than the lower temperature. Regardless, if it works, it works. And I recall trying that when I had a "shop fridge" and I believe it DID last longer. But I swear that stuff has a mind of its own - when it wants to cure, it cures and there's nothing we can do about it

Ed B

The tooling shop I worked in had a refrigerator just for super glue and locktite. Usually had someone's lunch in it as well.

And Temp changes that rate, which was the point here I believe.