Trouble shooting efficiency and Deadline Coffee Porter

One of the most popular topics of discussion in all grain brewing is maximizing efficiency. It's a broad and confused topic because there are a lot of variables to consider, and the terminology/metrics are not always consistent. For my purposes, I define the brew house efficiency (BHE) as the percentage of the total potential sugars in the grains transferred to the wort, as measured by the gravity of said wort at a well known volume. I think this is the most common definition of BHE, though some brewer's use other definitions. 

One point that irks me about BHE is people claiming that they can increase it via boiling. Sugar is a conserved quantity during the evaporation process, so regardless of whether you are measuring the pre-boil wort, or the post-boil wort, the BHE should be the same. You can use extra boiling to offset poor efficiency and hit target OG, but only the volume and SG have changed in this case -- not the efficiency. 

Personally, I'd really like a consistent BHE of 75% or so with typical (<1.060) OG beers (many brewers report a decrease in efficiency for high gravity brews). With my last two brews, I've hit 63% efficiency each time. The styles of the recipes haven't been particularly OG sensitive so I wasn't worried about missing the mark, but I'd like to raise the BHE and hold it consistent in the next few brews. A lot of the forums online describe various tips people use to increase BHE, but most of the people responding to efficiency queries are shooting in the dark. Recipe, equipment, etc. are not really enough to diagnose shortcomings in the BHE. Instead, I think that the most important step in diagnosing the problem is separating the BHE into its constituents: conversion efficiency and lautering efficiency. With this brew, I'm going to follow Kaiser's steps to figure out my conversion and lautering efficiency so I can zero in on the problem(s). 

The first thing I did was to take steps to insulate my mash tun. I've noticed that the lid feels warm during the mash compared to the sides. This suggests I'm losing temperature through the thin lid (it's a 48 quart Coleman cooler for reference). I struck a few degrees high and stirred until the grain bed hit the ideal temperature as measured with a meat thermometer. Then I wedged some 2" thick foam wrapped in tin foil a few inches above the mash (see the pictures). I used another layer of foam on top of the foiled layer and closed the tun with the lid. With this insulation, the mash held temperature for an hour with no measurable heat loss.

2" thick packing foam used for insulation

Wrapped in tin foil to avoid absorption

Foam wedged into the mash tun

Extra layer of foam for increased insulation

As I brewed, I collected samples along the way. I took a half-cup of first runnings and a half-cup of the pre-boil wort and put them in the freezer during the boil. I also added 2.25 gallons of tap water back into my tun after my sparge, stirred, and drained a half cup of runnings. I later measured the gravity of the first runnings (at room temp), and found them to have a gravity of 1.080. Knowing the volume of the strike water, I calculated the conversion efficiency at 89%. I measured the gravity of the post-sparge runnings at 1.016. Using Kaiser's lautering efficiency table, 1.016 corresponds to 81% lautering efficiency for a 2.0 qt/lb grist ratio (based on the volume of the cold water readdition). The gravity of the pre-boil wort, 1.056, allowed me to calculate BHE at 71% which is within a percent of the product of the lautering and conversion efficiency (1% error is well within the margins of measurement error in reading volumes, SG, etc.). After taking these measurements, I added the pre-boil wort and the first-runnings wort back to the kettle. 

The lautering efficiency is pretty decent for batch sparging as far as I'm concerned. The conversion efficiency should ideally hit 95%, however. Two majors players in limitation of conversion are mash pH and the crush of the grain. Using EZ Water and data from my water authority, I found that the mash pH should have been well within the acceptable range. Seeing as I did not verify this with strips or a pH meter, this not necessarily the case. That being said, I think it's likely my crush was not ideal. I crush my grains at my LHBS rather than with a personal mill. Many homebrewers suspect that stores will set their mills wide so that brewers don't complain about stuck sparges -- which conveniently helps them sell more grain. Given the steps I've taken to avoid a stuck sparge, I think I can afford a finer crush. Next time around, I'll run the grains through the mill twice and see if my conversion increases. Assuming a 95% conversion, I could easily hit 75% BHE in future brews.

I really don't know where the extra 8% efficiency I got with this brew came from. The crush in each case was likely similar as I used the same mill for both. The gravity was fairly consistent as well. It is possible that holding the temp. constant during the mash led to better conversion. Otherwise, my stirring technique at the dough in may have improved from previous batches. 

For this brew, I was aiming for something along the lines of the Berkshire Brewing Company's Dean's Bean's Coffeehouse Porter. I elected to make a nice and roasty base beer and use some coffee in the process too. There's a lot of discussion about how to introduce coffee to the beer. Some people brew espresso and add it to the boil in various stages, or cool it and add to the secondary or bottling bucket. Others use grounds in the mash, boil, or secondary. Beans can be used in the same way as grounds -- some report good results with 'dry beaning.' Personally, I decided to use cold-brewed coffee for this beer. I've heard good things from brewers and coffee aficionados alike on the smooth, non-astringent character of cold-brewed coffee. I will add a half cup to the bottling bucket to get a subtle coffee flavor in the batch to compliment the dark grain bill. 

Deadline Coffee Porter

Grain Bill

US 2-Row: 7 lbs (80.0%)

Crystal 60L: 0.5 lbs (5.6%)

Chocolate malt: 0.5 lbs (5.4%)

Coffee malt: 0.5 lbs (5.1%)

Roasted barley: 0.5 lbs (4.0%)

Single infusion mash @154 for 1 hour

Hop Schedule

Willamette (5% AA): 0.375 oz, 60 min

East Kent Goldings (6.4% AA): 0.375 oz, 60 min

Willamette (5% AA): 0.375 oz, 15 min

East Kent Goldings (6.4% AA): 0.375 oz, 15 min

Yeast

Fermentis Safale US-05 (one 11.5 g packet)

Stats

SRM: 40+

IBU: 29

OG: 1.062

Brew house efficiency: 71%

Batch size: 3.5 gallons

Notes

Brewed on 1/18/2014 

Ran off 2.25 gallons of first runnings (SG 1.080, 89% conversion). Sparged with 2 gallons of water at ~ 200F. Collected total of 4 gallons of pre-boil wort (SG 1.056). Boiled down to a 3.6 gallon batch (SG 1.062). Pitched rehydrated US-05, and left in ambient temperatures. Active fermentation within 12 hours.

2/8/2014

Ground fresh JP Licks espresso roast coffee very fine. Put 1 cup (liquid measure) of grounds, and 4 cups water in a Nalgene bottle. Stirred, shook and left in the fridge overnight.

2/9/2014

Strained the coffee (~ 3 cups yield), and boiled 2 cups along and dissolved the priming sugar for the batch directly in the coffee. Bottled as normal with the coffee/sugar solution.