Wednesday, February 24, 2021

Brew Day: 4PM Darkness (Imperial Stout)

Below is an unpublished post from 2019 I wrote for another website. In addition to a regular Brew Day post, I took more of a "how to" approach like I did in some of my earlier posts. 

I own four five-gallon glass carboys. When any of those carboys are empty it feels like a waste. Those carboys are taking up space in my basement when they could be aging some perfectly good beer!

With most of the standard strength ales I brew these days I don't bother racking to a secondary. Living in New England my basement is at a fairly steady 50 degrees during the winter. I can take advantage of the temperature to brew a lager and use one of my carboys for lagering. I can also use my carboys for aging sour beers or ciders. My favorite thing to use them for is to age high-alcohol beers. Long conditioning time in a secondary fermenter gives the complex flavors time to meld, and the alcohol time to mellow.

A year ago I brewed an imperial stout with my colleague Sven from Muntons. I took a recipe from a Gordon Strong book and adjusted the recipe to use ten different Muntons malts as a way to give Sven hand-on experience with as many of our malts as possible.

I was legitimately blown away with how great that beer came out. When I racked the beer after a week to a secondary it was delicious even then. I entered that beer into the National Homebrew Competition (NHC) where in the first round in Boston it won second in it's flight to advance to the final round.

While the beer didn't medal at the final round, and I didn't get my picture in Zymurgy, I did receive some solid feedback. I took that to heart while deciding how I wanted to tweak my recipe. At both rounds the judges thought the beer was maybe a little too roasty. At the first round in Boston the judges thought it was maybe a little too hoppy for a higher score. When the same batch was judged three months later, the hop flavor had subsided, but the judges still wanted more sweetness. With that in mind, here is the recipe I settled on:

Boil Size: 10.13 gal
Post Boil Volume: 5.63 gal
Batch Size (fermenter): 5.25 gal   
Bottling Volume: 5.00 gal
Estimated OG: 1.110 SG
Estimated Color: 77.6 SRM
Estimated IBU: 78.4 IBUs
Brewhouse Efficiency: 70.00 %
Est Mash Efficiency: 72.0 %
Boil Time: 180 Minutes

14 lbs           Maris Otter Pale Malt (Muntons) (2.6 SRM)        Grain         60.9 %             
3 lbs            Munich Malt (Muntons) (8.1 SRM)                  Grain         13.0 %            
2 lbs            Wheat Malt (Muntons) (2.5 SRM)                   Grain         8.7 %               
1 lbs            Chocolate Malt (Muntons) (520.3 SRM)             Grain         4.3 %              
1 lbs            Crystal 150 (60L) (Muntons) (76.1 SRM)           Grain         4.3 %               
1 lbs            Roasted Barley (Muntons) (634.5 SRM)             Grain         4.3 %              
8.0 oz           Black Malt (Muntons) (634.5 SRM)                 Grain         2.2 %              
8.0 oz           Crystal 400 (150L) (Muntons) (203.0 SRM)         Grain         2.2 %              
1.00 oz          Nugget [13.50 %] - Boil 60.0 min                 Hop           43.9 IBUs                 
1.00 oz          Northern Brewer [8.10 %] - Boil 30.0 min         Hop           20.2 IBUs               
0.25 tsp         Irish Moss (Boil 15.0 mins)                      Fining        -                      
1.00 oz          Fuggle [4.90 %] - Boil 15.0 min                  Hop           7.9 IBUs                
1.00 oz          Phoenix [9.80 %] - Boil 5.0 min                  Hop           6.3 IBUs                
1.0 pkg          Irish Ale Yeast                                  Yeast         -                       

Mash Schedule: Single Infusion, Full Body, No Mash Out
Total Grain Weight: 23 lbs
Name              Description                             Step Temperat Step Time     
Mash In           Add 7.39 gal of water at 167.9 F        156.0 F       90 min        

Sparge: Fly sparge with 5.60 gal water at 168.0 F

The only ingredients that a homebrewer might not be able to find are the Muntons Wheat and Munich malts. If you can't find those, I strongly suggest a quality imported substitute like Ireks White Wheat and Munich Malt.
Brewing high gravity beers like this does require some extra steps. Before I was with Muntons, I worked part time at a homebrew shop. When inexperienced brewers would come into the shop wanting to brew high gravity beers I would try to talk them through what to do. If I felt like the customer wasn't getting what I was trying to explain, or maybe didn't have the equipment needed, I would strongly suggest to the customer that they stick with a lower gravity brew.

Here are some of the challenges with high ABV brewing, suggested best practices, and what I did with this brew.
  1. Yeast Pitching Rate - A high alcohol beer requires a high amount of fermentable sugar, which in turn requires a high amount of healthy yeast to ensure a thorough and clean fermentation. 
    1. With liquid yeast this usually means making a yeast starter and/or buying multiple pitches. I used to hate making yeast starters on a weeknight to be ready to brew on the weekend. Free samples of Proper Starter pre-made starter wort from Homebrew Con hooked me on the product immediately.
    2. My favorite method for building up yeast cell counts for a high ABV beer is what I call a starter beer. Instead of making a 1.040 wort for the sole purpose of yeast propagation, I'll brew a batch of beer that is moderately hopped and has a similar gravity as a yeast starter. Bitters, Scottish Ales, English Porter, and Irish Stout are great styles for this method. For this batch I brewed an English Porter as a starter beer, which left me all of the yeast I needed for the imperial stout at the bottom of my fermenter. 
    3. If you don't have time to make a yeast starter or brew a starter beer, dry yeast is the easiest and cheapest way to go. Earlier this year I brewed an English Barleywine that got two packets of Nottingham. For any brew with an SG of over 1.080 I suggest pitching two sachets of dry yeast. No reason not to spend an extra $5-$8 to make sure your high ABV beer has enough yeast to ensure a full fermentation with no off flavors.

    4. I pushed my system to it's limit.

  2. Grist volume - When brewing a high ABV beer make sure your mash vessel can handle the volume of grain in your recipe and the strike water needed. I own a Brewers Edge Mash & Boil. The grain pipe in that system can only hold around 15 pounds of grain. Other brewing appliances of similar size like The Grainfather and RoboBrew have similar limitations. Instead of mashing in the Mash & Boil, I mashed in a ten gallon Igloo cooler. The grist and strike water filled the cooler to the very top. I could barley close the lid without pushing out hot mash water. Making sure you have enough room for your mash is just one reason to use a thick mash.

    Good luck batch sparging this

  3. Sparging - If your mash tun is as full as mine was, batch sparge or no sparge methods are out of the question. Fly sparging is your only option. That means you need a hot liquor tank with a ball valve that you can either gravity feed over your mash bed, or a pump to pump your hot liquor. If you don't have one, a sparge arm is a great investment to keep your grain bed level and avoid channels developing, which can lower your efficiency.
  4. Efficiency - Whatever mash efficiency you normally achieve on your system, expect it to go down. A consequence of needing more water for your mash is that you need less sparge water to achieve your normal pre-boil gravity. One way to compensate for this is to sparge for longer, then boil off for longer to end up with the same batch size. Goose Island does a 180 minute boil when brewing their Bourbon County beers. With this batch I planned to try the same method. To handle my pre-boil volume of 10.5 gallons, I had to use my propane burner. That meant I was outside in Massachusetts in December. When my propane tank ran low on gas I lost my boil. When I switched tank I was able to get a rolling boil, but I did have to boil for longer. I am also hoping the longer boil gives me some kettle caramelization to give the beer additional sweetness.  
  5. Malt extract is your friend - Some all grain brewers look at malt extract the same way an avid mountain biker might look at a toddler's trike. Well, you shouldn't. More professional brewers use malt extract than people realize. Muntons sells dry malt extract in 55lb boxes to professional brewers, and we sell them by the pallet. Instead of employing a long boil like I did on this brew, take a pre-boil gravity reading and adjust your gravity with DME to hit your target. The imperial stout I brewed last year with Sven got 13oz of DME after the mash. If you are brewing on a brewing appliance with a limited grain capacity, just replace some of your base malt with malt extract. It's that easy.
  6. Wort aeration - With a normal gravity beer splashing your wort in your fermenter will introduce enough oxygen into your wort. High ABV worts are a stressful environment for yeast. Your yeast will need more oxygen for a full and healthy fermentation. I ran an aeration pump for over half an hour while I was cleaning up from my brew day. That along with pitching plenty of yeast made sure my beer was fermenting within a few hours after pitching. 
  7. Temperature control - With all of the fermentable sugars in a high gravity beer, active fermentation is active indeed! That will generate quite a bit more heat than normal fermentation. Even if you pitch at the right temperature, the temperature can quickly rise too hot. With my beer I kept my fermenter in my 50F basement. and attached a heat wrap. I plugged the heat wrap into a temperature controller to keep my beer at a steady 68F

One way to avoid many of these steps when brewing high gravity beers is to just brew with malt extract and steeped specialty grains. All of the issues with mash volume, mash efficiency, and sparging aren't there. If you do a partial boil, the cool top-off water will also help aerate your wort. Malt extract will cost more, but brewing my recipe with malt extract would certainly have been quicker and easier.

This malt extract version of the recipe is pretty darn close to the all-grain recipe and a lot easier:

Recipe Specifications
Boil Size: 6.53 gal
Post Boil Volume: 5.99 gal
Batch Size (fermenter): 5.00 gal   
Bottling Volume: 4.60 gal
Estimated OG: 1.114 SG
Estimated Color: 61.8 SRM
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 0.0 %
Boil Time: 60 Minutes

Amt              Name                                             Type          #          %/IBU                
1 lbs            Chocolate Malt (Muntons) (425.0 SRM)             Grain         1          5.3 %              
1 lbs            Roasted Barley (Muntons) (525.0 SRM)             Grain         2          5.3 %               
8.0 oz           Black Malt (Muntons) (525.0 SRM)                 Grain         3          2.6 %               
9 lbs 14.4 oz    Maris Otter Extract (Muntons) [Boil] (4.6 SRM)   Extract       4          52.1 %            
3 lbs 4.8 oz     Amber Malt Extract (Muntons) [Boil] (10.4 SRM)   Extract       5          17.4 %             
3 lbs 4.8 oz     Wheat Malt Extract (Muntons) [Boil] (5.3 SRM)    Extract       6          17.4 %        
2.0 pkg          Nottingham Yeast (Lallemand #-) [23.66 ml]       Yeast         7          -                     

Steep the roasted malts, keep the hops the same as the all-grain recipe and either do a full-volume boil, or if doing a partial boil on the stove-top save half of your malt extract as a late addition. Also use water free of chlorine and monitor your fermentation temperature.

In the past I made an English Barleywine with a similar amount of malt extract and had excellent results. At NHC in 2017 the beer scored  a 37 and almost advanced in the competitive Specialty Wood-Aged Beer category. I still have bottles of that barleywine that I'll chill and open on special occasions.

That is really what the great thing about these big beers is. Most of what I brew is medium gravity beers I can keep on tap and enjoy for a couple or a few months. These big beers can be keepsakes. A beer you can brew to celebrate a milestone like a marriage, buying a house, or birth of a child. A homebrewed, high gravity beer, perhaps bottled and labeled, makes a great gift to any beer lover. If brewed and packaged well, these beers will keep for years to come. 

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