Or, The Devil is in the Details
I suppose I am a creature of habit. When I need two-part epoxy for a wargaming project - in this case, to attach rare-earth magnets to aircraft models - I go to Wal-Mart.
It seems like when I go to Wal-Mart, the brand names and descriptions of the products may change, but essentially the choice is binary: "regular" epoxy or "fast" epoxy, the difference being how long it takes the epoxy to harden once mixed.
However, I was unpleasantly surprised when I grabbed the "regular" two-part epoxy recently, only to see that the packaging now recommends this only for use with plastic. Hmmm... is this not the same epoxy I usually buy? So instead, I grabbed the other two-part epoxy, the "fast" one (which costs a little more).
Opening the blister pack, I found the contents were a bit different than usual: a dual-syringe filled with epoxy, and two long nozzles. I was disappointed as the quantity of epoxy seemed a lot less than before.
The directions were simple: Pull back on the plungers. Break off the end of the syringe (which exposes two openings). Push one of the nozzles onto the openings, and twist to secure it in place. Then depress the plungers to dispense the epoxy.
It turns out that the nozzles have little baffles in them, which means the epoxy comes out the end already mixed. (Instead of you having to mix the two-part epoxy together yourself.)
So I started gluing my magnets to my aircraft models... but before I had hardly started, the epoxy was spongy and useless, already well on its way to hardening. What???
OK, time to read the packaging. Turns out I hadn't bought "fast" two-part epoxy. I'd bought Instant Mix epoxy, which sets in 40-60 seconds and is hard within five minutes!
Not to say that this isn't a seriously cool product, if you need super-fast two-part epoxy. The nozzles are one-use-only, so with two nozzles you'll only do two projects for each package.