GOOD NEWS: DON’T THROW OUT THAT WEAK BEER!!!
I had fantastic results using this method. I think variations of this method it could work with almost any style, whether all-grain or extract, as long as you use an alcohol-tolerant yeast like Nottingham.
I organize group extract brewings in garages, up to 5 or 6 Bayou / Turkey burners and kettles going. I’m always answering questions, helping grind grains, measure hops, etc. --distracting me from my kettle.
Somehow my last 10 gal. batch of Samuel Smith Oatmeal Stout clone (in 2 corny kegs) came out really light and weak. I was neither willing to throw it out or force myself to drink 10 gal. of weak beer I was too embarrassed to give away.
METHOD:
I took approx. 2-1/4 gallons of this weak beer from each (4.5 gal. total) corny keg and put it in my brew kettle, along with (approximately):
2 oz. KENT GOLDING
2 cups SUCROSE (table sugar)
12 oz. MOLASSES
8 oz. BLACK ROASTED BARLEY
12oz. CHOCOLATE MALT
(I also added 4 shots of espresso from my machine)
I did a 60 min boil --yes, I basically re-brewed, using BEER instead of water.
I added around 1 gallon of filtered tap water when I chilled the beer/wort, and poured it back onto the original NOTTINGHAM yeast bed (from both fermenters combined into one pale) in a fermenter.
Fermentation took off that night aggressively and came to a pretty sharp halt around 1 to 2 days later. It’s possible all those yeast quickly devoured the fermentables, but also possible that the alcohol content climbed so high it killed off the yeast, though Nottingham has a fairly high tolerance for ABV. I let it go around 12-14 days and re-kegged it, adding around 3 shots of Everclear.
RESULTS: Good as ever - great oatmeal stout, heavy sigh of relief, & hefty stout supply for the Fall.
THOUGHTS: Since initial character was established by the Nottingham ale yeast, I wonder if using a higher gravity (ex. Belgian, or champagne/wine yeast) would more fully ferment available sugars w/o throwing off the flavor too severly?
Cheers,
Mark in the U.P. of Michigan