We recently decided to attempt what we thought was a simple experiment. We wanted to brew two batches of the exact same beer and then dry hop them with different hops to see how dry-hopping affected the overall aroma and taste and to better understand the aroma characteristics of the hops we were using.
We chose to brew an Imperial IPA for this experiment for a couple of reasons. One, we love big IPAs. Two, the recipe we were using was a partial mash and uses a healthy does of Pale Malt Extract (10lbs in each 5-gallon batch) in it, which we believed would even out some of the potential differences in efficiency from the mashes we would make.
Our brew set up remains very simple and we set to getting both mashes going at the same time. We have two gas burners, kettles, and we used sleeping bags to control the mash temperatures. Nothing fancy and we’ve done it many times before, but not brewing the same beer. We did 60 minutes mashes and 60 minutes boils for each. We used the exact same ingredients. With all these similarities, I expected the results to be about the same.
Batch #1 came out with an original gravity of 1.070. This was much lower than I expected – we were shooting for an OG of 1.10. Hmm.
Batch #2 had an OG of 1.082 – also low, but considerably higher than batch 1. WTF?
So there are two main questions:
Question 1: Why were the original gravities so much lower then our targets?
Question 2: Why was there such a large discrepancy between the OGs of the two batches when we used the same recipes, brewed them at the same time, etc. Clearly our mash and brew methods are different.
I’m going to tackle question #2 first – the discrepancy between the OG of Batch 1 and the OG of Batch 2.
Brew Kettles: In both cases, we used 6 gallon brew kettles for both the mash and the boil. But there are differences between the kettles. Kettle 1 was stainless steel and short and wide, kettle 2 is aluminum and tall and narrow. As a result, the mashes may have acted differently, even though we tried to keep them at a mash temp of 151 degrees. The difference in kettle shape and material may also have been
Mash and Sparge equipment: We used two pretty significant methods for mashing an sparging. Since we only had one lauter tun, we opted to use a grain bag for Batch 1 and then sparged the grains by pouring water through the grain bag. For batch 2, we mashed the loose grains in the kettle and then dumped the grains into the lauter tun and sparged from there.
My theory is that the difference in OG between the two batches is a result of inconsistencies between the batches during mashing and sparging, since we added 10 lbs of extract to each kettle later. Equipment clearly matters, and can result in pretty significant results.
Back to question #1 – why was our OG so much lower than our target of 1.100? I think the answer here is simple – we mashed at the incorrect temp. I need to research this more.
And then this happened.
The top blows off the Imperial IPA.
At around 2am on the night we brewed a loud POP! wakes me up. The lid off the bucket blew and painted my ceiling, walls, and kitchen appliances with deliciousness. Idiot. I should have used a blow off tube from the beginning. I’ve made this mistake too many times before. Here’s a quick little video of the yeast doing their thing after I put the tubes in:
Today, one week after brewing, we racked and dry hopped the IPAs. Interestingly, they both have the same gravity at rack – 1.041. This means that Batch 1 is currently at 3.8% ABV and Batch 2 is at 5.4% ABV. Way low for the end of primary fermentation for a beer this big.
Imperial IPAs Dry Hopped with Cascade (left) and Citra (right) Hops
10 hours later, however, and fermentation has kicked back into gear in the secondary.
Imperial IPA reactivated in the Secondary
Next week, we’ll keg these things. Cannot wait to see how they turn out. Stay tuned.