Another batch, another question

Discussion in 'Homebrewing' started by butterygold, Jun 21, 2020.

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  1. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    Hello again,

    I am having trouble understanding this. Today I brewed a Creature Comforts Tropicalia clone that I tweaked a bit (slightly different grain bill, Idaho 7 and Motueka instead of Galaxy and Mosaic). I did an all-grain BIAB with my new 10 gallon kettle. I had 13 pounds of pale ale malt, 2 pounds crystal and 1 pound flaked oats. I started with 5 gallons, then did a 2.5 gallon dunk sparge, which some of you suggested doing. The pre-boil gravity was 1.036 with a 1.041 target. So far, so good (?).

    But, I ended up with 4.25 gallons of wort (target 5) with an OG of 1.058 when the target was a 1.066. According to an OG/FG calculator, this gives me an efficiency of about 45%. I used the finest setting on the mill, and squeezed as much as I could out of the bag.

    Still don't know what I'm doing wrong. Thanks in advance
     
  2. VikeMan

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

    Is that 4.25 gallons of wort into the fermenter, or in the kettle after the boil? If the former, what was the volume in the kettle? (i.e. did some wort stay behind in the kettle?)
     
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  3. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    Sorry - 4.25 gallons is what went into the fermenter.
     
  4. VikeMan

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

    So, when computing mash efficiency, you need to know the post boil volume in the kettle. Just trying to scope the size of the problem. Do you know what was in the kettle?
     
  5. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    There was very little left in the kettle when I poured it into the fermenter. 2 mesh bags with hops and maybe a 1/2 cup of sludgy liquid.
     
  6. VikeMan

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

    How many ounces of hops were in the boil, and what kind (i.e. leaf or pellet)?
     
  7. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    2.5 ounces of Idaho 7 pellet and 2.5 ounces of Motueka pellet divided between 30 and 10 minutes of boil.
     
  8. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    What I don't really understand is that I was pretty close to a pre-boil gravity that was calculated at 75% efficiency and that would yield 5 gallons.

    I got 4.25 and an OG that calculates at roughly a 45% efficiency. I even used an extra 2 pounds of grain, as somebody on another thread suggested doing.
     
  9. VikeMan

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

    Ok, so estimating....
    4.25 gallons + 0.03125 gallons (sludgy trub) + 0.125 gallons hop absorption =
    ~ 4.41 gallons post boil

    What was the temperature of your post boil wort when you measured the gravity?

    What was your pre-boil volume? And at what temperature was the pre-boil wort when you measured its gravity?
     
  10. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    Post boil temp 80F. Temp calculator bumped the OG up to 1.059.
    Pre boil volume 7.5 gallons, temp of measurement was mash temp of 152º.

    VikeMan, thanks for taking the time to answer all this.
     
  11. MrOH

    MrOH Grand Pooh-Bah (3,995) Jul 5, 2010 Virginia
    BA4LYFE Society Pooh-Bah

    Your not taking the water absorbed by the grains during the mash into account.
     
  12. VikeMan

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

    @butterygold Was 7.5 gallons the total amount of water you used? Or did you have 5 gallons of wort left in the kettle after hoisting the bag, which you then dunked in 2.5 gallons of water?
     
  13. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    7.5 was the total amount used. I filled the large kettle with 5 gallons, did a 90 min. mash, dunk sparged in the smaller kettle with 2.5 gallons, then 'fly sparged' with .5 gallons so that the small kettle was at exactly 2.5.
     
  14. VikeMan

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

    I'm still not clear, but bear with me, because it matters for figuring out what the mash efficiency actually was...

    5 gallons in the mash
    pulled bag and dunked in 2.5 gallons
    0.5 gallons came from where? New added water?
     
  15. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    Believe me, I appreciate this help. The 0.5 was boiled water that I poured through the bag into the big kettle.
     
  16. MrOH

    MrOH Grand Pooh-Bah (3,995) Jul 5, 2010 Virginia
    BA4LYFE Society Pooh-Bah

    OK, so it sounds like you're not taking the malt absorbing some of the water into account, but further clarification may help. I would expect to lose 2-3gal to the grain with that amount, depending on freshness and how patient I was with runoff. Did you measure the total volume of wort you had before you started the boil?
     
  17. VikeMan

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

    Ok. The 0.5 gallons was additional water, into the big (not the small) kettle. So let's say there was a total of 5 + 2.5 + 0.5 = 8 gallons of water used.
    Lets estimate that 16 lbs of grains trapped about 1.9 gallons of liquid (0.12 gallons per pound). So...

    8 - 1.9 = 6.1 gallons pre-boil kettle volume

    So, if your pre-boil was 6.1 gallons and the gravity was 1.036 at 152F, corrected for temp to 1.056:
    6.1 x 56 = 342 points

    And post boil was 4.41 gallons and the gravity was 1.059:
    4.41 x 59 = 260 points

    Should be the same points for both, but the big difference tells me there is something off in one or more estimates or measurements somewhere.

    Using your post boil numbers and reasonable assumptions about your grains (PPGs), I'm calculating about 45% Mash efficiency. Using your pre-boil numbers, I'm calculating about 59% mash efficiency.

    Neither number is great, but 59% is a whole lot better than 45%. Again, the fact that they are different points to an error somewhere.

    Are you sure the pre-boil wort was really at 152F (mash temp) when you measured the gravity, and hadn't lost some heat? If it had, that would make the adjusted-for-temp pre-boil OG and mash efficiency lower (i.e. would make the pre-boil measured mash efficiency closer to the post boil measured mash efficiency).

    A few thoughts.

    - Any measurement error... weight of grains, wort volumes, temperatures, hydrometer readings... affect the computed mash efficiency

    - You say you used the finest setting on the mill. What did the crushed grains look like? Perhaps take a picture next time.

    - How sure are you of your actual mash temperature? How much did it vary? Is your thermometer calibrated? How did you maintain the temperature? (If you were very far off, you could have got poor conversion.)

    - Who weighed your grains and how?
     
    #17 VikeMan, Jun 22, 2020
    Last edited: Jun 22, 2020
  18. Brewday

    Brewday Zealot (721) Dec 25, 2015 New York

    If i made this recipe batch sparging it would be something close to 7-1/2 gals for mash and 2/3 for sparge. Collect 7/6-1/2 and boil to about 6/5-1/2 depending on gravity.
     
  19. butterygold

    butterygold Devotee (343) May 12, 2020 Spain

    I did not. Maybe a stupid question, but what's the best way to do that? The kettle has no markings on it...
     
  20. VikeMan

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

    Get a wooden dowel. Add "X" gallons of water to the kettle, dip the dowel, and mark it at the water line. Measure smaller increments proportionally (by length) and mark them.
     
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