Russian Imperial Stout with Bourbon Soaked Oak - Take III

This will be my third attempt to make a Bourbon Soaked Oak Russian Imperial Stout inspired by Goose Island's Bourbon County Brand Stout (Read about 1st and 2nd attempts).  As I found in recent Head to Head Comparison between my beers and a 2017 BCBS, the beers I've made so far are tasty but lack the intense whiskey character of the real thing.

My first beer was oaked with 4 oz of charred and toasted oak sticks I prepared myself out of lumber and then soaked in Makers Mark.  Finding that the first lacked whiskey character, I reasoned that the Makers Mark being 45% and barrel aged spirit being 60% was a significant difference.  So, for the second attempt, I soaked my oak in Everclear diluted down to barrel strength and I then oaked the beer with 5 oz worth of sticks.  This was still not enough.  This also wasn't helped by the fact that second beer only fermented down to 1.055 which also contributes to a significant difference in balance than the original.  My conclusion from the first two rounds:  

1. Barrel proof spirit was an improvement
2. Oak preparation seems good as far as I can tell
3. I used too little oak in these batches

I think the base beer I'm making is good enough to get me close to the real thing.  It seems clear to me that the "magic" of BCBS is in the barrel aging (no shit, right?  I'm a slow learner).  We can determine quite a bit about their oaking levels based on some simple analysis:

Whiskey barrels are about 53 gal each.  The internal surface area of a 53 gal barrel is about 56 square inches per gal.  In my previous batches of beer I've added oak considering the weight of the oak rather than the surface area which, in retrospect, I think may have been a mistake and one of the key contributors to my beers not matching the whiskey character of BCBS.

I'm using sticks that are about 1 in x 1 in x 6 in (see how I made them here).  This is about 26 square inches each.  In order to match the surface area of a whiskey barrel I'd need to use 2 of these sticks per gal which is 12 per a 6 gal batch.  I used the equivalent of 3 or 4 in my last batches.  

This doesn't consider that my wood has end grain exposed to the liquid while the barrels do not.  Putting that aside for a moment, I think we can get some interesting insights into the absorption capabilities of a barrel based on the following analysis:

The base beer is 11.75% ABV per the BCBS spec sheet (we assume they're still aiming for that).  After spending months in fresh whisky barrels the beer has increased in alcohol.  Suspect this is due to the barrel proof spirit absorbed in the wood which then intermingles with the beer during aging in a non-climate controlled warehouse.  Doing a bit of math we can derive how much barrel proof spirit is added per gallon of beer to get to, for example, a 14.1% ABV (which is the ABV of my last remaining 2017 BCBS):

• 1 gal of base beer contains 128 oz
• At 11.75% ABV this is about 15 oz of alcohol
• At 14.1% ABV this is 18 oz of alcohol
• So, we've picked up 3 oz of alcohol per gal
• Barrel strength whisky is ~60% ABV.  
• So, to get 3 oz of alcohol you'd need 5 oz of barrel proof whisky added per gal

As a sanity check, this would mean that in a 53 gal whiskey barrel there is about 2 gal of spirit absorbed in the wood.  This seems to me to be fairly believable.

Finally, another data point on the absorption capabilities of my oak with end grain:

• I have been soaking oak in the Everclear diluted down to ~60% ABV over the last year
• I measured the weight of 4 sticks of my oak be 11 oz prior to the soak.  This now weighs 20.4 oz
• Therefore, we've picked up 9.4 oz of spirit by weight 
• 1 cup of this spirit (8 oz by volume) weighs 7.4 oz
• The 9.4 oz of spirit by weight is ~10 oz of spirit by volume
• So, 2 sticks would get you the 5 oz of spirit which matches the per gal absorption of the barrel

Now, drum roll, please . . .

It appears that Two 1 in x 1 in  x 6 in sticks of oak per gal provide the correct surface area to match a 53 gal whiskey barrel, absorb enough alcohol to increase the base beer from 11.75% ABV to 14.1% ABV when the alcohol is released, and match the absorption rate of a real barrel closely despite the end grain

Based on this analysis, I'm going to try out a very dramatic increase in oaking for this batch, from 3-4 sticks last time, to 12 for a 6 gal batch.

I'll stick with the same base beer but, based on the findings from the higher than ideal FG last time (I measured the gravity of real BCBS at 1.038), I'm going to pitch extra yeast to restart a stuck fermentation if I end up much higher than my target of 1.040.  I'll start out with a second pitch of Wyeast 1028 (London Ale) for this but also have some White Labs 099 (Super High Gravity) to add in if a stall occurs.

I'll let this beer ferment out for a month or so prior to moving to secondary.  It should be a very agressive fermentation so I'm going to split this into 2 fermenters at first to prevent loss of beer due to blowoff.  Oak will be added in secondary and I plan to age it until next summer up in my attic (where I've been aging the oak).

Recipe Details:

• Grain:
• 14 lb 2 row
• 10 lb English Style Pale Malt
• 8 lb Light Munich
• 2 lb Crystal 60L
• 1.5 lb Chocolate Malt
• 1.5 lb Roasted Barley
• 12 oz Black Patent
• 4 oz Acid Malt
  
• Hops:
• 3 oz Chinook (Leaf, 12.2% AA) at 60 min
• Yeast:
• Wyeast 1028 London Ale Yeast (2nd Pitch)
• White Labs 099 Super High Gravity Yeast
• Water:
• 20 gal spring water
• 2 tsp CaCl
• 2 tsp Gypsum
• 1 tsp Irish Moss at 15 min
• Extras:
• 12 sticks (1x1x6 in) of White Oak Soaked in 60% Everclear

Process Details:

• Batch Size:
• 7 gal (Target 6 gal)
• Mash:
• 153 F for 60 min
• Boil:
• 4.5 hrs
• Fermentation Temp:
• 68 F
• Primary Duration:
• 4 weeks
• Secondary Duration:
• 6-8 months

Results:

• OG:
• 1.135 (Target 1.129)
• Efficiency:
• 70.52% (Target 57%)
• FG:
• 1.040 (Target 1.040)
• Apparent Attenuation:
• 68% (Target 65%)
• ABV:
• 12.8% (Target 11.75%)
• Note, with the whisky soaked oak this would be up to ~15% ABV
• (6.25 gal of total beer * 128 oz/gal * 12.8% ABV + 12/2 sticks * 3 oz Alcohol/ 2 sticks)/6/25 gal * 128 oz/gal
• (102 oz + 18 oz of Alcohol)/800 oz of Total Liquid = 15%

Brewing Notes:

• 8/1/20 - Made a couple 1.5 L starters and added in a couple jars of yeast slurry from my last Barleywine.  Not a lot of obvious activity by the next morning (this yeast started slow for me last time as well but ended up doing the job so I wont worry too much about it)

• 8/2/20 - Brewday - 9:30 AM to 7:30 PM- Including setup and cleanup
• Brought 10 gal of spring water up to 185 F
• Milled half the grain for this batch.  Found that I was missing the Crystal 60L.  Had to go to the HBS across town to get it which will add 2-3 hrs to the brew day.  Will do it during the first mash

• Added half the CaCl and Gypsum to the grain
• Moved 7 gal of water into the mash tun and cycled through the RIMS at 163 F until everything had evened out
• Stopped the RIMS and added the grain.  Stirred in well to eliminate dough balls
• Mashed for 2.5 hrs.  It went from 154 F to 151 F over that time
• Sparged with the remaining warm water left from the strike
• Did a modified fly sparge by ladling water on top of the grain bed while I drained
• Started heating after collecting 4 gal.  Collected until I had about 8 gal
• Boiled the beer for 2 hrs

• Collected the liquid from the mash tun into a separate bucket to use as strike water for the next mash
• Cleaned out the mash tun
• Brought 10 gal of spring water up to 185 F for the next mash
• Milled the second half of the grain
• Added remaining CaCl and Gypsum to the grain
• Added strike water along with previous mash runnings to the mash tun and cycled the RIMS until it has settled out to 163 F

• Stopped the RIMS and added the second half of the grain.  Stirred well to eliminate dough balls
• Let it settle for 10 min and then cycled the RIMS at 153 F for 60 min
• By the end of the first 2 hrs of the boil the wort had been reduced to 3.5 gal
• Sparged the mash into the boil kettle using the same modified fly sparge method until I had 11.5 gal of wort total
• Boiled for another 2 hrs.  Had many slight boil overs and had to adjust the heat level quite a bit over the course of this second half of the boil.  I decided to add 30 min to the boil towards the end.  With about 8 gal left I found that my Brix was 28 so I decided to just boil down to 7 gal which would be about at my target SG of 30
• With 60 min left I added the bittering hops

• With 15 min left added the Irish Moss
• With 5 min left added the Wort Chiller to sanitize
• Once the boil completed I chilled to 80 F
• Had about 7 gal of beer at this point
• Measured the gravity as 31.5 brix (1.135).  I decided to let this ride as I'd added about 2.5 L of yeast starter to this which was maybe an OG of 1.05.  This would water it down slightly.
• Transferred the beer evenly to 2 fermenters.  Pitched the yeast during this transfer - they had started showing a good amount of activity over the last couple hrs of the brewday. Yeast added about half a gal of volume.  Let the beer fall about a foot to aerate
• Moved the fermenters to my chest freezer set at 68 F
• 8/3/20 - Airlock was bubbling aggressively by this afternoon
• 8/7/20 - Fermentation looks to be about done.  I'll give it another week before checking gravity
• 8/15/20 - Measured the gravity as 1.054.  I'm going to pitch some WLP 099 - Super High Gravity yeast to try to get this down a bit further.  Made up an all grain starter and set it on a stir plate
• 8/16/20 - Lots of activity in the starter.  Pitched the whole thing into one of the two fermenters.  We'll see how far this takes it before I decide what to do with the second fermenter.
• 8/18/20 - The airlock bubbled again yesterday and then into this morning.  I have the fermenter out of the fermentation chamber where it's in the low 70s.  Will check the gravity again this weekend
• 8/27/20 - The airlock bubbled for about a week.  I checked the gravity again today and found it has dropped to 1.050.  I was hoping for a much bigger drop.  Flavor wise it seems a fair bit less sweet than it had been though so definitely an improvement.  

• 8/29/20 - Transferred the beer from the two fermenters into a fresh one.  Ended up filling almost to the top so close to 7 gal still.  I scooped in maybe a couple cups of yeast slurry from the fermenter that had the Super High gravity yeast in hopes that it will come down some more.  Measured the gravity of the mixed beers as 1.048.  This is lower than the sample from a couple days ago which was taken from the spigot at the bottom of my SS BrewTech fermenter.  I wonder if there may have been a bit of settling/stratification going on that made for an inaccurate gravity reading.  Anyway, I'll let the beer sit for another couple weeks to ferment a bit more.
• 9/2/20 - There has been active airlock activity for the last few days after the combination of the beers and transfer into a fresh fermenter.  I don't see how the beer couldn't be dropping further in gravity.
• 9/6/20 - Checked the gravity again today - down to 1.045.  Tastes quite a bit less malty and sweet than it had at 1.055.  Hopefully it will keep going down a bit more for me.
• 9/13/20 - Airlock has continued to slowly bubble over the last week.  Measured the gravity again and it had dropped down to 1.042
• 9/20/20 - Measured the gravity again and found it's down to 1.040.  Decided to transfer into secondary along with my 12 oak pieces for long term aging.  Putting it in a fermenter with no pressure relief mechanism in the hopes that pressure forces beer into the wood like occurs with a barrel.  I'll keep this in the basement for a couple weeks to monitor pressure build up and then move it to the attic to be exposed to temperature variation

• 10/4/20 - The fermenter hasn't really gotten any more pressurized here in the last couple weeks.  I think it's low risk of bursting at this point.  I've moved it up to the attic to age for the next year.  Fall is starting to set in so it's getting cool at night and staying in the low-70s and below during the day - hopefully this will start the process of extracting spirit from the wood.
• 12/26/20 - I did a side by side tasting of the beer and a 2019 BCBS today.  The beer has been aging in the attic where it's been warm and then very cold as we've transitioned to winter.  It has an alcohol bite to it that is approaching BCBS (closer than the previous versions I think) but isn't quite equal to it.  It also doesn't have close to the oak flavor of BCBS yet.  It definitely needs more time on the oak (pleased that it wasn't quickly over-oaked in the last 3 months.
• 1/24/21 - Moved the beer down to the heated bedroom to warm the beer up a bit and hopefully cause some exchange of flavor with the oak
• 6/14/21 - I put the beer back up in the attic 4 months ago or so and it's been through the cold of winter and now the hot of the start of summer.  Decided to do a comparison with BCBS (2020 version)
• Aroma:  Very close in terms of intensity of whiskey character (agressive) - mine might be a bit stronger actually.  Both have chocolate and coffee coming through behind the alcohol.  \
• Flavor:  Both beers are front and center about the whiskey character.  I'd say they are very close in terms of strength.  The flavors between them are a bit different.  Mine has a bit of a fruity character that blends with a more sweet chocolate character.  The real thing is maybe more roast focus.  Very close and tough to do a real tasting between beer pulled from secondary and a carb'd beer from the bottle
• Overall:  I'm very encouraged by what I'm getting out of the extra oak here.  I'm going to give the beer another 5 months of aging  (as planned) to see how it goes.
• 11/20/21 - The beer sat in the attic all summer and now it has cooled off as the nights are in the 30s.  I'm thinking it's about time to bottle and decided to do a pre-bottle tasting:
• Aroma:
• Strong booze and oak along with a prominent chocolate and roast aroma.  There is caramel and dark fruit mixed in as well for good measure.  Very complex
• Flavor:
• Strong boozy and oak flavors up front followed by a sweet chocolate, roast, and caramel flavor.  There is a bit of bitterness in the finish which is then overwhelmed by a strong alcohol flavor and oak.  Very, very rich flavor profile.
• Overall:
• It's a really good beer and I think the strength of the alcohol is very close to what BCBS provides (not drinking it side by side this time to say for sure).  It's boozy but not quite like a real bourbon flavor.  I suspect my oak preparation is the source of some difference - I'd bet my toasting is a bit more agressive than what they're doing which makes for a more caramel flavored spirit. 
• 12/29/21 - Bottled today with a pack of Red Star Premier Cuvee Wine yeast and 4 oz of sugar.  Measured the gravity of the beer as 1.040 (so no drop over the last year).  Collected about 6.25 gal which got me 46 BCBS bottles (which are 16.9 oz) of beer.  I'm going to let this carbonate up over the next couple weeks before trying the first one

• 6/13/22 - Tasting Notes - Boldly flavored and booze forward beer.  It is pretty complex with the rich malt and whiskey/oak derived character.  The oak character itself seems quite a bit different than a typical bourbon - a lot more caramel and no vanilla really.  The oak is certainly very smooth - it is definitely not over-oaked to my palate.  As a BCBS clone I think (and I'll post a proper side to side comparison on this) my beer is very close in terms of boozy presence but the character I got out of the oak was significantly different from the real thing