Recipe Formulation with Water Calculations

In this post, we will formulate a new recipe and calculate the needed water amounts at the same time. This is not a big deal since the only real water change is the amount of water absorbed by the grains. Because we do not yet know the amount of grains we will use, we calculate the water from the target batch size back until we get to the water absorbed by the grains. At that point, we are able to calculate our grain amounts and then complete the water calculations. Rather than just talk about this process, I want to demonstrate the steps needed so that it serves as a complete example for reference.

Before moving on, I feel I need to make something clear: The Original Gravity (OG) and Final Gravity (FG) measurements are both taken from my fermenter. The OG is measured prior to adding the yeast for fermentation, and the FG is measured after fermentation has completed. This is important, and I did not make this distinction previously which could lead to some confusion when talking water amounts used in calculations.

OK, I am excited about this recipe because it is a first attempt at cloning my favorite beer: Goose Island's Bourbon County Stout. In this post, I do not want to get into my feelings towards the InBev purchase of Goose Island, so I will just summarize that my initial optimism and acceptance was turned sour by the discovery/learning of the unscrupulous InBev corporate views of the craft beer industry and their unethical business practices. So, all the better if the beer can be replicated at home. On to the recipe....

As I mentioned, I am excited to try and brew this beer, but the recipe guidelines are not from me. The grains and hops used are from the Goose Island description linked above; The gravity values used are from a post in the HomeBrewTalk forums (using the 2007 version of the beer); The grain percentages used are also from a post in HomeBrewTalk. Here are the specifics we are using:

Recipe Parameters

Parameter	Value
Batch Size (fermenter volume)	3.25 gal.
Target Original Gravity	1.13
Target Final Gravity	1.042
Color	Black ~100 SRM
IBU	60 (assume Tinseth method)
Length of Boil	80 min.
Mash Steps	Single infusion 152°F for 60 min.
Brewhouse Efficiency	70%

Grains

Grain	% Used	Max Extraction	Color (°L)
2-Row	34	37	1.8
Munich	30	34	10
Chocolate	14	34	350
Crystal 60	10	34	60
Roast Barley	10	25	300
Debittered Black (Briess Blackprinz)	2	25	500

Hops

Willamette 3.5% to 6.0% AA @60 min. ~4 oz. (TBD)

Yeast

Safale US-05 Dry Yeast 3 packets

STEP 1: Calculate Initial Water Amounts

Remember that the constants used in finding water amounts are specific to my system. Your values may be different. In some cases they are just guesstimates waiting for me to collect more accurate information

• V_final = 3.0 gal (amount in bottles or keg)
• bottling losses: ~ 0.25 gal.

• V_fermenter = 3.25 gal.
• Transfer and trub losses: ~0.75 gal.

• V_post-boil = 4.0 gal.
• Temperature shrinkage: 4% ~ 0.2 gal.
• 80 minute boiloff: 2.34 gal.

• V_pre-boil = 6.5 gal.

This is as far as we can get without knowing the grain amounts.

STEP 2: Estimate Grain Amounts

To summarize the values of interest here:

• Original Gravity: 1.13 (130 Gravity Points)
• V_fermenter : 3.25 gal.
• Brewhouse Efficiency: 70%

     ► Total Gravity (GT)

GT = Gravity Points * Volume

GT = 130 * 3.25

GT = 422.5

This is the total number of gravity points in our fermenter that we need to be contributed by the grains.

     ► Individual Grain Contributions to Total Gravity

Here we use the percentage of each grain used to determine the amount of gravity points each individual grain contributes.

Grain	Percent Calculation	Grain Contribution
2-Row	0.34 * 422.5	143.6
Munich	0.30 * 422.5	126.7
Chocolate	0.14 * 422.5	59.2
Crystal 60	0.10 * 422.5	42.25
Roasted Barley	0.10 * 422.5	42.25
Blackprinz	0.02 * 422.5	8.5

     ► Grain Amounts Needed to Achieve Gravity

Now we use the individual gravity contributions, the maximum gravity that can be extracted from the grain and our brewhouse efficiency to find the grain amount. Here is the equation used:

Grain Gravity Contribution / (Brewhouse Efficiency * Max Extract Points)

Grain	Formula	Value (lbs)	Value (lbs And oz)
2-Row	143.6 / (0.7 * 37)	5.5 lbs.	5 lbs. 8 oz.
Munich	126.7 / (0.7 * 34)	5.3 lbs.	5 lbs. 5 oz.
Chocolate	59.2 / (0.7 * 34)	2.5 lbs.	2 lbs. 8 oz.
Crystal 60	42.25 / (0.7 * 34)	1.8 lbs.	1 lbs. 13 oz.
Roasted Barley	42.25 / (0.7 * 25)	2.4 lbs.	2 lbs. 6 oz.
Blackprinz	8.5 / (0.7 * 25)	0.5 lbs.	0 lbs. 8 oz.
TOTAL:		18 lbs.	18 lbs. 0 oz.

STEP 3: Calculate Remaining Water Amounts

We now continue where we left off calculating our water amounts. Our last calculation was for the pre-boil volume, so we start there:

• V_pre-boil = 6.5 gal.
• Transfer loss: ~0.25 gal.
• Grain Absorption: 18.0 lbs. * 0.2 gal./lb. = 3.6 gal.

• V_total = 10.35 gal. ≈ 10 gal. 1.5 qt.
  
  

STEP 4: Calculate Mash and Sparge Volumes

For my mash, I am going to use 1.3 quarts of water per pound of grain. Also, remember that I have a full 4 quarts of space under my false bottom in my mash tun, so that needs to be added to the mash water.

V_mash = 1.3 qt/lb * 18.0 lbs + 4 qt

V_mash = 27.4 qt ≈ 6.85 gal. = 6 gal. 3.5 qt.

The sparge volume is now just a matter of subtracting the mash volume from the total volume.

V_sparge = V_total – V_mash

V_sparge = 10.35 gal – 6.85 gal.

V_sparge = 3.5 gal. = 3 gal. 2 qt.

Since I doubt I am 100% correct, I will make sure I have probably 5.0 gallons of sparge water available. I will just need to make sure I hit the proper volume in my boil kettle while watching the gravity readings of my runnings.

Conclusion and Remaining Information Needed

So that is it for calculating our grains and water. Of course, there is some information missing in regards to brewing the recipe:

1. We really didn't do anything with the hops. We know the IBU we need to hit, and I mentioned that we are using the Tinseth method for IBU calculations. Through that, we can estimate our hop amounts (it also depends on the actual %AA of the hops you purchase). Maybe this will be my next post.
2. Based on the gravity and volume amounts, I believe the 3 packages of dry yeast will be sufficient for this big beer. One thing we did not cover is the fermentation schedule (times and temps). This will definitely be racked to a secondary fermentation where we will allow the beer to sit on bourbon-soaked oak cubes for probably 6 months. I am not 100% sure, but I will probably let this sit in primary for two weeks; with week one being at a cooler temperature of maybe 60 degrees or so, and the second week at around 68 degrees. The secondary will be 6 months, and that temperature will probably be the same 68 degrees (not a lot of options for my basement).
3. Speaking of bourbon-soaked oak cubes, how much bourbon and how many cubes? Since we only have 3 gallons, I am assuming one 1 ounce cube. As far as the bourbon, I am not sure yet (amount or brand). I used Makers Mark and oak chips for my last beer and was less than happy, so this time I am moving to cubes and some other bourbon brand.

So these are questions that still need to be answered, but we are well on our way to making a first attempt at our clone. If this recipe doesn't work out, we get to drink what will probably still be a great beer and then try again. If it does work, we make more. Truly a win-win.