Re-fermentation Experiment

[Bourbon_Knight]

So, I was doing another generation of CFW, using inverted sugar on top of backset from my previous generation, and hit a SG of 1089.
Aerated my wash, added a capful of DAP, and added the washed whiskey yeast also collected from the previous run.
(Just for the record, this is where I think I went wrong!!)

Things were looking good.
The initial fermentation seemed to go well, however after a couple weeks the bubbling stopped, so I checked the FG.
1035! :handgestures-thumbdown:

Stirred the fermenter sediment up a bit, and added the brewing heat belt.
Bubbling started again after a day, albeit slowly.

Two more weeks on, and it's stopped, so measured my FG again.
1030! :crying-blue:

Had thought of dumping another batch of new yeast in the fermenter to deal with the stuck ferment, however I was aware I only had bakers yeast on hand, and the calculated wash was already at 7.6%, so I decided on a different tack.
(To be honest, I had already waited so long for this batch, and was really in the mood for a stripping run), so I racked the wash into the boiler and ran the strip.

Once finished, and it had cooled to 20degrees, I measured the backset pH as 3.1, and the gravity surprisingly still at 1030.
Kinda makes sense - I've removed most of the available alcohol from the fermenter during the stripping run, leaving me with an acidic wash of 1030.

Whilst the backset was cooling, I rehydrated some Lowans.
Adjusted the backset pH to bring it up to 4.9 (wanted slightly higher but didn't want to push adding too much adjuncts).
Aerated the 'wash' with the stick blender, then dumped the rehydrated Lowans into the fermenter.

Within 30 mins it's started bubbling away.
I expect it to pick up over the next 24 hours.

Lessons:
1. I'm surprised that it seems I can re-ferment a failed wash to reclaim the unused sugars.
I'll update the progress.

2. learned that after 3 re-pitches, it seems I've stressed my whiskey yeast beyond performance.

3. also learned that I should just do the math going forward and keep the gravity to a sensible level, and pitch enough Lowans/Saf Gold to handle it.

In the long run, I would have been able to get more product running multiple batches of lower gravity wash than in the time it's taken me to process this single high-gravity batch.

Happy to dedicate one my second fermenter to see if I can get the remaining 3.9% alc that I was owed from that wash. :pray:

FWIW - the flavour of the 7.6% I did get was quite nice.

Happy with the CFW - looking at also trying a TFFV soon.

[RC Al]

The generational washes mainly stall from ph.
Simply adding more water to get the ph up and not as much sugar would have kicked off the next generation just fine too.

Good lesson to learn on the lower abv washes. Lower abv leads to cleaner ferments with less off flavors from stressed yeast - unless its rum :D