I had a bottle of "masteron" (drostanolone enanthate, actually) and a bottle of trenbolone enanthate, both unused for over a month and only one mililiter left in each.
Tren bottle: a brown, smoke-like whisp of something was suspended in the bottle.
Drostanolone bottle: brown spots on the bottom of the bottle. Like a bacteria colony in a petri dish.
Possible Cause: The dirty air that we inject into our bottles takes up a substantial volume when only one mililiter is left in the bottle. Given a month, and gear with low alcohol levels, it is possible that some bacteria could grow.
I disposed of both bottles because I figured they were contaminated with bacteria. What do you guys think?