Hello gentlemen. Yes I'm a newb and I apologize if this question is common knowledge among professionals, but I didn't really find a definitive answer from searching. I was wondering if anyone knew of a way to extend the shelf life of epoxy primer hardener/catalyst/activator once the container is opened? If it makes a difference I am referring to Shopline JP375 epoxy primer, but I suspect that it probably applies to most 2k epoxy primers. Both the manufacturer (PPG) and the jobber (Single Source) have told me that once the hardener is opened and exposed to air it will only have a shelf life of another 2-3 weeks. I realize that the hardener is relatively cheap, but I need to use just a little bit this week and won't need to use the rest of it for another 3-4 months, but I'd hate to waste a lot of it just because I cracked open the can for a few ounces. I don't remember if I read this here or elsewhere but iirc someone said that in addition to reclosing the can as quickly as possible, blowing the C25 gas mix from a mig welder into the can helped to preserve it. Can anyone confirm whether or not this is true, or if it is just another bit of online misinformation? Any other advice? Thanks in advance to everyone for your help!

Tom

The wood industry I am in is about the worst in creating "waste" materials stuff. Years ago guys started using that c25 (75% argon and 25% Co2) and it does help. Later though, it was found that pure argon was even better. Bloxygen is pure argon designed specifically for this. Simply open up your can, take out what you need, then quickly blow in the Bloxygen.
Another cheap fix can be using clean marbles or ball bearings to quickly displace the amount of material that you just used, bringing the level as far up into the neck of the can as possible.

very interesting i'm amazed at the things I learn at my age, and I thought I knew everything. on the catalyst thing I don't ever remember having a problem with epoxy catalyst. I was thinking it was a different cure process than urethanes or enamels. some urethanes and enamel catalysts are a problem. my idea here was that some are moisture cure and some are more chemical cure, epoxy being the later chemical cure. I may be all wet here so whip me if you want.
Jay D.

Yeah, most of us have just enough chemistry background to be dangerous, ha, ha When I was young I remember you'd walk into old wood shops and see their varnish and spar varnish cans upside down......What's up with that, dad???? Varnish starts skinning on top.....now the skin is in the "bottom" of the can.... When needed they would then flip and pour off the good varnish for use.....
On the argon thing....it does work but as you said we've got such a variety of materials that results can be mixed......