I had some epoxy left over from a project two years ago and I tried to
use it. It seemed to have separated into a watery top part and a
thicker milky bottom part. The whole mess smelled like ammonia.
Nevertheless, I did use some of it by mixing it very well. It took a
long time to cure but it did work. A couple of weeks later, it had
gotten so that I could not even mix it so I had to throw it away. I
am wondering if moisture had condensed as water in the container
somehow but this would be a lot of water, almost a half gallon.