How to Kettle Sour

So, ever since Kev's bachelor party in Asheville, I've been digging on sour beers. Finding them is still kind of hard, even in a place like Davis, which has some great local beer resources. And they're always stupid expensive. Turns out, brewing sour beer is just complicated microbiology with the goal of getting drunk. So, that got me back into brewing beer, after not having done it since grad school. And it's immensely satisfying to turn $20-60 worth of ingredients into the equivalent of $500 worth of a trendy, unique beer.

There's a fair bit of elitism out there on the internet in terms of the "best" ways to make sour beer. There are dozens of ways to go about it, but the traditional method is to prepare wort with a very small amount of hops, and then ferment for 6 months, if not years with a blend of microbes, commonly coming from the dregs of another bottle of unfiltered and unpasteurized sour beer.

But, fuck all that. You can make a really good sour beer in three weeks. Here's how I'm doing it:

What you need, in decreasing order of difficulty:
- a way to incubate wort at 90-120F. (I use a mini-fridge with a small space heater inside hooked up to a temperature controller)
- a way to measure pH between 3 and 5, maybe. (You can spend a chunk of money on a pH meter, or you can spend $5 on some pH paper, or just use your tastebuds. As an organic chemist who's had to maintain and calibrate plenty of pH meters over the years, fuck that. pH paper works fine.)
- 88% lactic acid
- some Dried Malt Extract
- Something you can ferment 2L of wort in. (I have some 1/2 gal mason jars with screw caps I can put an airlock on)
- about a liter of carbonated water
- uncrushed grain (this is the source of your souring bugs. Grain is crawling with lactobacillus, the same bacteria used to make yogurt, sauerkraut, kimchee, etc and it's happily and symbiotically living inside your gut right now. I believe now that sourcing lacto from grain gives you a healthy, wild population with more complexity than you're likely to get from probiotics or prepared cultures.)

Steps:
(A) Make a wild lactobacillus starter.
- Prepare 1/2 gal cheapo wort with DME, boil for a few minutes to sanitize.
- Pour into bottle/jar until 3/4ths full. Let cool to about 100F.
- Add 1/2 teaspoon of 88% lactic acid to reduce pH under 4.5. An acidic environment helps lactobacillus start off healthy, and hurts gross bugs.
- Add 1 cup uncrushed grain, then top off with carbonated water to get rid of most headspace. This gets rid of most of the oxygen, which doesn't bother lacto, but will prevent other gross bugs from taking hold easily.
- Incubate at 90-110F for about three days.
- Taste it! It probably won't kill you. I've not made a bad starter this way, but I would imagine if it tastes the usual bad way, it's going to be vomity, or fecal. My good starters taste kind of like tomato soup. You can check the pH, and it will probably be 3 or under, meaning pretty acidic.

(B) Make your wort, but don't add hops.
- Mash like you normally would.
- Bring it to a brief boil after mashing. (no hops!)
- Cool to around 110.
- Pour in your lacto starter (through a strainer to get rid of the grain).
- Add carbonated water from an unopened bottle to purge some oxygen
- Cover with plastic wrap to keep oxygen out
- Let it sit in your 90-110F incubator until pH drops to about 3.3

(C) Boil and ferment like normal
- Boil to kill the lacto off, and prevent the wort from getting too acidic
- Add your boil hops. You probably want to keep this under 10 IBU, as bitter and sour is not generally a tasty combination
- I like to ferment with a nice, clean, fast American yeast, like US-05.

Random thoughts:
- If you want interesting flavors, try adding 5-10 lbs of fresh fruit for a week or two after gravity is stable for a few days.
- You can sour pretty much any base beer, though I'm told roasty malts make a bad combination.
- Lacto doesn't floculate much at all, so this beer is probably going to be pretty cloudy. A cold crash helps a little bit. Gelatin didn't do a whole lot when I tried. Tastes fine though, so fuck it.
- This won't make a funky beer. Funk ("barnyard" or "horseblanket" flavor and taste) comes from a long, starved Brettanomyces incubation. I don't like these kinds of beers as much, though. YMMV
- Some people will say that kettle souring doesn't make for an interesting, complex beer. Meh. Have fun waiting a year for your complex beer that might or might not have barely detectable depth, and might well go rancid. I don't have room or patience for that.