Lessons Learned: Recipes, Mash Efficiency & Fermentation Temperature

Last summer we brewed an Alpha King clone recipe out of Brew Your Own magazine. We had yet to brew an insanely hoppy beer, and this looked like just the ticket. To add to our excitement, the guys over at Half Acre gave us a bunch of their ale yeast to use (like almost a half gallon of it).

The brew day went well, we pitched a little over half of the Half Acre yeast, and that same night we were off to a very strong fermentation. The following day it was going bananas. We had it in the coolest room in the house, but the temperature was still around 68-70F in there. The second day, I checked the sticky-strip thermometer on the side of the fermenter, and noted that it was a good 5 degrees higher than the room's ambient temperature. WOW! I said. Look at that.

A couple weeks later, we racked to the secondary and dry hopped. A quick taste during the gravity reading was very nice. Excitement building!

After bottling and conditioning, it was time to sample the first bottle. Hmmmm... it's quite a bit darker and thicker than we expected, but dang - lots of hop goodness! Yet it's bordering on imperial. We're still quite pleased. But as time went by that hop flavor started to diminish, and other flavors started to come to the forefront - namely an alcohol burn. What the hell is going on here???

Since I brewed this I picked up a copy of BeerAlchemy - and plugged in my brewday numbers. Holy crap - this is an 8% beer! And wow, we got an 80% mash efficiency! Hmmmm... mash efficiency. Having only a handful of all grain batches under our belt at the time, this was something I wasn't used to. I wonder what Brew Your Own is assuming for mash efficiency? After checking it out, I note it's a paltry 65%. No wonder this beer is so strong! I should have scaled the grain bill down a bit, but we had no idea at the time. So that was mistake number one.

Mistake number two was fermenting at too high a temperature, which explains the solvent, rubbing alcohol type flavor - or "heat" of the beer. I had this issue in a previous batch, but didn't put 2 and 2 together because it was sort of an experimental batch anyways - so now I know. Fermentation temperature is key, and ales do better in the low 60's vs. the low 70's. I guess I knew this before, but now that I know what this mistake tastes like, I hopefully won't let it happen again.

For our next brew (a stout), I surrounded the fermenter with plastic bottles full of frozen water that I would swap out a few times a day as they thawed (I have a home office, so that's easy enough). I wrapped a big towel over all that to sort of make a fermenting-tipi. I kept the temperature right around 68, which was perfect for the stout, which I'm pleased to say turned out very well - phew! I'll have to see if I can get our second fridge to hold at 60F or higher (since we actually use the freezer, we can't hook-up one of those temp-control gadgets).

Now that winter is approaching, I'm looking forward to brewing some ales and more easily maintaining the proper temperature. I'll probably stick to belgians and lagers next summer.

So anyways, I hope these lessons can help someone out ;)