If you spot some UFO’s (unidentified floating objects) in your bottle of vinegar, or perhaps a little cloudiness, you’ve probably got a vinegar mother on your hands. If you leave it alone, the natural bacteria in the vinegar will continue to work, and the mother will get bigger. Think of the mother as a sourdough starter, but for vinegar. You can use this hunk of gunk to make yourself more vinegar. Or you can just chuck it: strain it out with a coffee filter, and your vinegar will be no worse for wear.
To make more vinegar, follow Sherri’s advice: “Put the mother in a clean jar. Add leftover wine and pretty soon you’ll have wine vinegar developing. I have a jar beside my kitchen sink and religiously add the last inch from my glass. Let it age for a bit and enjoy!” Non Cognomina adds that once the mother has done its work and the wine is pure vinegar, the mother will sink to the bottom of the jar. It’s still alive; you can rescue it and used it to make another batch.
Unidentified floating objects in vinegar