Sunday, February 28, 2010

#34 BWB (BABBs Wild Brew)

Brewed: 19th February, 2010

This beer is part of a collaboration brew for the brewing club I belong to. The idea is that about 22 members will brew up the same recipe and ferment it out under the same conditions (well, as close as possible anyway), then the resulting beer will be blended together and aged in an ex-wine barrel with another yeast strain. At the end of the year, we will bottle off half of the barrel and then brew a new beer (possibly a different recipe) and blend it with the remaining half of the beer and the cycle will start again. More details, including the recipe, can be found on the BABBs website.

With an estimated original gravity of 1.104 SG, this was by far the biggest brew I've ever attempted. The grain alone for this batch weighed in just under 8kg; three kilograms more for the same volume than the usual grain bill for the Summer Ales I have been brewing over the recent months. As I still only have a hand mill, I was lucky enough to get the grians pre-milled!

I was a little surprised to see that my system was able to extract the necessary amount of sugar from the grain for such a large volume, with my pre-boil gravity coming in just above the calculated expected value and getting more volume than I had anticipated. I think this was partly to my mis-calculation of sparge water volumes, resulting in first-runnings of 20 litres instead of the expected 14! I adjusted the second sparge to account for this mistake. I'll have to look into this calculation again for future big beers so I don't make the same mistake again.

The gravity of the second runnings was indeed high enough that I decided to sparge one more time and get 5 litres of additional sweet-wort from the grain. It's still sitting in the fridge (after being boiled) waiting for me to make a decision about what to do with it.

My evaporation rate wasn't quite as high as I predicted, and as a result, I needed to boil the wort for two and a half hours instead of the predicted two. It probably could have done with an extra 10 minutes on top of that to hit the target OG spot on, but it was close enough in the end.

The biggest mistake I made on the day was that I didn't notice that my kettle drain filter had become blocked towards the end of draining, and I assumed that it had finished emptying. This resulted in me leaving behind 3 litres in the bottom of the kettle instead of the normal 1 litre I usually lose, and pretty much canceled out the great extraction efficiency I had during mashing. I think the blockage was partly caused by the wort being a lot more dense than I am normally used to - yet another lesson learned.

These were my results from the brewday:

Mash time: 60 minutes
Target mash temperature: 65C
Start: 65C End: 63.5C

Runoff: 30L

Pre-boil SG: 1.068
Boil time: 150 mins

Post-boil volume (hot): 21L
Target OG: 1.104 Actual: 1.101

Volume in fermenter: 17L
Yeast: Wyeast 3787 Trappist High Gravity
Ferment temperature: 18C for first 24h, then up to 24C

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