Rio's Stop-flow mold shelf-life

Has anyone else ever had a jar of Rio’s Stop-Flow mold when left
alone for a month or so? I had not been doing a lot of soldering work
for the last couple months, and when I opened my Stop-Flow tonight I
got a surprise. Nasty black and green mold. Black and gooey on the
surface, green fuzzy on the sides. And once scraped off, the texture
wasn’t the thick smooth liquid anymore, but rather a chunky sludge.
There’s no shelf-life date on the jar, but I’d guess that this jar is
over a year old. I guess I’ll have to add a jar to my next order.

A little weirded out,
LJ
Dreaming Dragon Designs