I can make vinegar!
Really it's the bacteria.
I can set up conditions hospitable to the organisms that make vinegar!
On the left is my second(!) batch of Czech Pilsner malt vinegar. I may have mentioned that this beer tastes like wet newspapers. That grossness is totally gone in the vinegar. I made some salad dressing with the first batch and it was really good. It does not seem as strong as the store-bought 5% vinegar, but I don't know yet whether that's because it's really not as strong or if it's still got some sugars and alcohol in it because it's still young. Learning!
On the right is the Ginger Bug starter that will go into my Ginger Beer. It's starting to get actively bubbly, so I think it's time to get on with the brewing for that. But this post is about vinegar...
Here I'm starting a new batch of malt vinegar using some Kentucky Bourbon Barrel Porter that tastes like ashes from too much black malt. I started it with 1 bottle of beer, ~6 oz of "finished" malt vinegar with its mother, and 1/4 cup of table sugar. Degas the beer, stir in the sugar, pour in the vinegar, and plop in the mother. I put finished in quotes, since the fact that this batch regrew its own mother just a week after being strained from its old mother tells me that it's not completely finished; also, as I mentioned above, it's not as strong as some of the commercial vinegars I have.
The addition of a significant amount of finished vinegar helps acidify the mix right away and prevent the growth of mold until a new colony of bacteria can get established. I'm starting to get a cycle going, and pretty soon I want to have three or four kinds of vinegar going, one bottle finished in use, and one batch with the mother colony in process. Then when it's ready, I can split the active batch, strain some for use, and feed the rest with more beer/wine/cider/etc to keep things going. Vinegar also seems like a great thing to give away once things get going.