Stouts, vatting, and souring

[sweetnighter]

I'm looking to put together a recipe for a classic Guinness-esque domestic stout. I've read up about "vatting," whereby you make a batch of strong stout to ferment with a brettanomyces or lactobacillus for a couples months, which is then later mixed in with a fresher batch of weaker strength stout. Has anybody done this? and how on earth would I calculate ABV if I'm blending the byproducts of two fermentations with two OGs and FGs? "Designing great beers" refers to the process but doesn't go into further depth. Any insight?

 

[Suthrncomfrt1884]

I did the clone in BYO 150 a few years back. It involved brewing an "extract" stout base. I say extract because it was basically a thick syrupy black liquid. Then, after I pitched my yeast into my pale beer, I siphoned off a little bit into a 22oz. bottle and added a little brett to it. I let this ferment out for a few weeks, then brought the mixure to 160 degrees. I combined the pale beer, the coloring "extract", and the sour beer in one.

It didn't taste exactly like guiness, but it came pretty darn close.

 

[Oldsock]

To calculate the alcohol you'd just do a weighted average. For example 4 gallons of 3% beer and 1 gallon of 6% beer it would be (4*.03+1*.06)/(4+1)= 3.6%

Blending can certainly give you some complexity, make 5 gallons of the big funky version and have some for drinking and some for blending.