I took 300mL of mead and separated it from the rest. Placed it in an open 1 gallon glass jug and shook vigorously to oxygenate
Day 2-4: Shaken vigorously daily and left in necked open bottle.
Day 5: decanted into and out of a beaker to measure the volume (listed as 300mL above)
Day 14: Still smells of alcohol rather than acetic acid. Shook again to oxygenate.
Day 16: A little mold on surface. Shook the entire bottle (mixing mold into the alcohol) to oxygenate.
Day 28: The scent has become considerably more vinegar-y.
I am reminded of some old pieces of pottery my grandmother kept: large, cylindrical glazed containers with 5-8 gallon capacities, with no lids whatsoever. She called them vinegar jars, and I'm left wondering if they didn't lack ceramic lids because they were meant to be covered with cheesecloth, allowing oxygen in but (perhaps) not mold. I'll have to look into that.