Process: pickling mustard greens.
The top had a thin layer of white slime, which would get into the water and float around as clouds if you moved it too much. After opening it and skimming, we found no particular odor or discoloration or foul taste, seems fine. Speculation is that it’s a wild yeast that briefly thrived on a less-saline part of the water, but was quickly out-competed by the highly salty water and anaerobic bacteria.
Four days is definitely not long enough to get the flavor, should be closer to a week minimum. We’re expecting that the recommendation of waiting two weeks is about right.