Skin on Balsamic Vinegar
I was doing some house cleaning, and when I got to the kitchen, I noticed a skin, much like what you see on warm homemade puddings and the like, on top of my Balsamic Vinegar, and another mass toward the bottom of the bottle.
I keep my Balsamic Vinegar and Olive oil in oil bottles, with an open pour spout.
I was wondering if this is just due to evaporation and the vinegar is reducing as it would naturally during production of more expensive vinegars, or if this is something that is potentially hazardous, and I should toss my vinegar and think of a new storage method.
Any insight would be greatly appreciated.