Figuring Efficiency (some questions)

Discussion in 'Homebrewing' started by BedetheVenerable, Aug 14, 2012.

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  1. BedetheVenerable

    BedetheVenerable Initiate (0) Sep 5, 2008 Missouri

    Several of you made helpful suggestions as to why with my recent mini-mashes I was getting pre-boil gravities a full 5-10 points shy of where they were supposed to be. My sparge water temp was low, and I was using equipment to sparge that was not ideal. Also, I likely had my BeerSmith software set way too high (at 75% efficiency) for my equipment.
    This past weekend, I did my first all-grain batch, after having set my software to what I figured was a still optimistic 70% efficiency. My first AG batch was an English Mild, 5 gallons:

    -3 lbs Maris Otter
    -3 lbs. Briess Mild Ale malt
    -12 oz. English Extra Dark Crystal
    -4 oz. flaked maize
    -4 oz. Fawcett Pale Chocolate
    -4 oz. Crisp Amber malt

    -1 oz Fuggles (4.2% AA) 60 minutes

    -2L starter of a two-to-three month old Wyeast 1469 smack pack.

    My pre-boil gravity came in 4 pts. higher than my software expected (at 1.037) and my original gravity was at 1.043, also 4 pts. higher than my software suggested. How do I, an idiot when it comes to math, figure out my efficiency? Is there a simple way? I'd like to get my software set to about my average efficiency, so I can moniter various batches and see how differing techniques work. I will tell you what; if all-grain goes this smoothly, I may never extract brew again, except in rare cases!
     
    #1 BedetheVenerable, Aug 14, 2012
  2. VikeMan

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

    The simplest way, since you are using software and already have the recipe saved (thus your expected gravities), would be to change the assumed efficiency upward until the expected gravities match what you actually got. Or, you could take your 1.043 OG and reverse engineer the answer...

    Expected Efficiency = 70%
    Expected OG = 39
    Actual OG = 43

    43 / 39 = 1.103

    70% x 1.103 = 77.2%
     
    #2 VikeMan, Aug 14, 2012
  3. BedetheVenerable

    BedetheVenerable Initiate (0) Sep 5, 2008 Missouri

    Thanks VikeMan! Is there any easy way to do this from scratch, say if I didn't have my software? I do, obviously, but I was just wondering if I happen to brew at a friend's or something like that, is there an easy way to calculate? PS, the 77% is great news!
     
    #3 BedetheVenerable, Aug 14, 2012
  4. DrewF

    DrewF Initiate (0) Jan 3, 2010 Pennsylvania

    #4 DrewF, Aug 14, 2012
  5. VikeMan

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

    If you know the points per pound per gallon (PPG) of your grain(s) (for example Maris Otter is usually 38 PPG), you can multiply that number by the pounds of grain used, adjust for expected mash efficiency, then divide by the number of gallons of (post boil) wort. So let's say you're using 10 pounds of Maris Otter in 5 gallon batch, and assume 75% efficiency...

    (38 x 10) = 380 theoretical points
    380 x 75% = 285 expected points at 75% mash efficiency
    285 / 5 = 57 gravity points

    So you're expected post boil OG would be 1.057.

    In practice, this is a little over-simplified, because it ignores other losses (which would affect brewhouse efficiency). So software or a spreadsheet is really the way to go.
     
    #5 VikeMan, Aug 14, 2012
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