Brew in a bag varying efficiency

Discussion in 'Homebrewing' started by tronester, Mar 12, 2013.

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  1. tronester

    tronester Pooh-Bah (1,653) Nov 25, 2006 Oklahoma
    Pooh-Bah

    I've brewed all the batches of beer brewed at my house for the past several years in the BIAB method. The small pot i have only allows for ~2.5 gallon batches which is fine for me.

    The odd thing is the wildly varying efficiency that I get. I brewed an English style mild last year and got a fantastic 80% efficiency. I just brewed a tripel this weekend and got a paltry 63%. The big difference between the two is that the tripel is twice as strong and used much more malt. I have a barley crusher and crush my own malt. However I can't remember if my LHBS crushed the malt for the mild or if I did. Can crushing too fast or too fine cause efficiency issues?

    Also the mild used Thomas faucett MO and the tripel used Rahr pilsner malt, could this be part of the issue as well?
     
    #1 tronester, Mar 12, 2013
  2. VikeMan

    VikeMan Grand Pooh-Bah (3,067) Jul 12, 2009 Pennsylvania
    Pooh-Bah

    In general, efficiency is somewhat lower with higher gravity worts. It's because more wort is left in the grains instead of reaching the brew kettle for a given pre-boil volume.

    Generally, it's the opposite. A crush that is too coarse decreases efficiency.

    What potential yield values (i.e. potential Points per Pound per Gallon (PPG)) values are you using? They might be different. Also, the Pilsner malt may have more enzymes (diastatic power for the mash) than the MO. If so, the MO might take longer to fully convert itself and any specialty grain starches.

    Edit: Also, make sure you're comparing apples to apples. Were the actual wort volumes the same, and if not, did you consider that in your efficiency calculations?
     
    #2 VikeMan, Mar 12, 2013
  3. liebz15

    liebz15 Initiate (0) Mar 23, 2011 Florida

    I have moved on from BIAB (I currently run a 15 gallon HERMS and batch sparge) but I have noticed (in BIAB and on my HERMS) that total grain volume has a lot to do with efficiency. When I would push my BIAB system's limits with a high grain volume, my efficiency would be much lower than running a low gravity. It probably has some to do with the density of your grains. The more grain you have, the more packed down it will get and thus the less surface area exposed to the water/wort. Just my opinion.

    My efficiency for regular BIAB was 65-69%, BIAB on top of a false bottom was 72-74%. And sadly, I just rebuilt my HEARMS setup and am currently struggling to exceed 70%..though I was nearly 82% before my rebuild.
     
    #3 liebz15, Mar 12, 2013
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