There is a forum member AJ80 that is reknowned for his sours at the Vic case swaps. He gave me some advice a while ago about how to do and easy kettle sour - the following is copied from his PM to me.
Really glad you liked them mate. Here's a thread that covers a couple of different ways to do it (bugs in the fermenter, sour mash and kettle souring):
http://aussiehomebrewer.com/topic/70585-sour-beers/page-10
I also took pretty heavily from this video (except i kettle soured as opposed to the mash):
https://m.youtube.com/watch?v=ohhXiKwYYsg
And finally, here's an overview of what I did:
- lauter into kettle as normal (my grist was 50/50 pilsner and wheat malt with an OG of 1.032)
- add some chilled water to bring it down below 50C
- add 500g uncracked pilsner malt in a hop sock to the wort (can be any base malt, just not a crystal as the higher kilning temps kills the lacto bugs)
- cover the surface of the wort with glad wrap.
- purge the headspace of your kettle with CO2 as best you can.
- lid on and seal it best you can.
- using a temp controller (ah the joys of an electric setup!!), keep at 40C until it hits your desired level of sourness. My brew was 50 hours, but it'll depend on your random inoculation rate from the pilsner malt.
- I re-purged with CO2 after 24 hours. The CO2 is to inhibit aceterbacter (or however it's spelled - the bug that makes vinegar). It loves oxygen. 40C is also important for this.
- keep tasting til you hit the right level for you (it'll taste ok, but smell like hot sick for the first 24 hours and then like sourdough after a bit).
- skim the scum off top and bring to boil.
- I did a 30 minute boil with a whopping 8IBUs of a neutral hop at 30 mins.
- cubed and then fermented at 16C with notto yeast to keep it clean.
I have follwoed the above instructions and made a pretty reasonalbe sour. the process is pretty easy if you have the ablitity ot maintain the temp at 40C . My kettle has an electric element so it was easy.
My only other tip form follwoing this is that when he says keep tasting until you hit the right level of sour...keep in mind its unfermented wort which is very sweet and hides the true sourness. I think I went a bit too far on mine. By the time all the sugar fermetns out it can be quite a bit more sour than you think it would be.
@AJ80 - hope you see this and chime in with more of your sourness and wisdom