There must be acid in the air

I'm trying to wrap up acid year (you might recall these resolutions are on a lunar cycle, even though I have already started the new one) and acid ideas just keep popping up.
My brother and sister-in-law gave us more fermentation books for Christmas, I opened a (non-acid) new cookbook yesterday and the page fell to recipes for pickled carrots and kimchee and flipping through today's mail led me to a bon appetit article on making one's own vinegar with this conclusion:

Making vinegar reminds us of a love affair.  As in all great romances, you must pay attention to its needs, take care of it, and have patience as it ages and transforms into something beautiful.* 

Vinegar and love affairs: there is clearly still acid left for me to explore.
*Hamilton and Hirsheimer (2013) "Sour Grapes" bon appetit. February 2013.  p. 62.