I bought a juice extractor last year, and pulverized some local apples with the intention of letting the liquid ferment into hard cider.
I must have looked the other way for a few extra days, though, because when I got back to it, it was already vinegar.
Really good vinegar. Complex, fruity, pleasantly acidic. Wow, what a trick.
It got used up pretty fast, so I bought more apples for juicing this past summer. I set the juice out in the open air, in glasses covered with cheesecloth, just as I had done the spring before.
But it didn't work. I got mold.
So in the fall I decided to just buy some cider already pressed from the Sebastopol apple guy (sorry, don't know the orchard), and I told him what I wanted to do. He said to do nothing. Easy, that I can do. He said the wild yeasts I wanted to "catch" in the cider were probably already present in the juice. I simply peeled off the foil liners inside the caps, returned the caps, and watched vinegar happen.
It worked this time, but not as acidic and not as complex.
Funny thing, nature. I'm so clearly not in control.
Back when I was experimenting with my juice extractor, I juiced a couple of raw beets. Wouldn't that make the most amazing vinegar, I thought.
But, no. I left the bloody ooze out for weeks, and it just turned syrupy, and eventually kind of vile. The juice was way too thick. Haven't worked out the bugs yet.
Still, I couldn't stop thinking about beet vinegar.
A couple of weeks ago I roasted some beets (unpeeled, in a covered casserole with a splash of water). The interior of the casserole came out a fantastic smear of baked-on fuchsia, so I poured in a little water to soak overnight.
Next day, the beet smear had all dissolved into a beautiful pink puddle, and it reminded me of my failed beet vinegar project. On a whim, I stuck my finger in and tasted it. Vinegar.
Magic! In just one day, some rogue fungus that had probably been lodged on the beet skin turned the rosy water into a lovely, gentle vinegar.
It was too small an amount to bother with, but... Wait. There's a little headroom in one of those cider vinegar bottles.
Ah, yes. In it goes.