Back to beer.

Over the course of a few posts, I described a method devised to accurately predict the brewhouse efficiency using a batch sparge process. I guess you could call it my sparge hypothesis, and if it is then we must experiment to find out if it seems to explain reality. Almost like *real* scientists.

The most recent batch I made was an English IPA. I targeted a batch size of 18.0 liters, with an OG of 13.6 °P (1.055 sg). Between me and my recipe formulator I came up with the following grain bill:

Mash Grains / Adjuncts |
% Yield |
Weight |

Marris Otter |
82.0% |
3.400 |

Crystal 10 |
75.0% |
0.200 |

Crystal 60 |
75.0% |
0.150 |

English Brown Malt |
70.0% |
0.100 |

Red Wheat Malt |
81.0% |
0.070 |

This is a total of 3.92 kg of malt with a predicted brewhouse yield of 78%, based on a mash conversion efficiency of 90% (note: I also added some golden syrup to this recipe, so the mash numbers do no reflect the total amount of fermentables in the final wort). Therefore I was targeting 2.48 kg of fermentables solely from the wort itself.

Using my usual water to grain ration of 3, my mash in water volume was 11.8 liters, to be topped up with 4.4 liters prior to the first runoff. The second runoff called for an addition of 10.3 liters. My targeted boil kettle volume was 22.5 liters (at mash temperature) with an OG of 10.7 °P.

How did I do?

Well, excellent, thank you. At the end of the mash and sparge I had 23 liters of wort at 10.7 °P. Not bad. My final brewhouse yield was 79%, and my mash conversion efficiency was 91%. At the end of boil I had 18.9 liters at 13.3 °P (1.054), of which about 17 liters ended up in the fermenter. All, in all, a pretty good job.

So, pat myself on the back and go on, right? Well, not quite so fast. Upon digging deeper, there are some anomalies to be found. Look at the data results:

For the first runoff I was expecting 11.7 liters at 15 °P. Calculations predicted 10.30 kg of water and 1.82 kg of fermentables. I measured 13.0 liters of wort at 15.1°P, which consisted of was actually 11.5 kg of water and 2.05 kg of fermentables. The second runoff should have consisted of 10.3 kg of water and 0.66 kg of fermentables. Instead I calculated it was 9.5 kg of water and 0.46 kg of fermentables.

So why did that happen? I am not sure, but it motivates me to take a look through old data and continue to keep meticulous records on future batches. Because, after all, it ain;t rocket science.