Conversion over 100%

Discussion in 'Brew Sessions' started by dstieglitz, Mar 12, 2013.

  1. dstieglitz

    dstieglitz New Member

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    Hi--

    I am starting to get the hang of the various conversion variables, and in my latest batch I am seeing a conversion of 125%... which can't be right, can it?

    I entered everything as close to correct as I could, using the total mash water as all the water input into the system and took a gravity reading pre-boil after everything was drained.

    My question is, what role does the recipe play in this calculation? If I have the wrong items in my recipe could this be the culprit?

    If so, how do I correctly match the recipe items to the grains I've bought from, say, Northern Brewer?
     
  2. LarryBrewer

    LarryBrewer Active Member

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    The highest conversion efficiency I have gotten is 102%, so 125% sounds really high and something is likely off. Please post all the details of the volumes collected, gravity reading, and the grain bill with amount and ppg and we'll check it out.

    You could also try plugging it into Kaiser's spreadsheet and compare that way:
    http://braukaiser.com/documents/efficie ... ulator.xls

    (our numbers match the spreadsheet)
     
  3. dstieglitz

    dstieglitz New Member

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    Here's the grain bill, everything was mashed:

    7 lb United Kingdom - Maris Otter Pale 38 3.75 50%
    1 lb United Kingdom - Black Patent 27 525 7.1%
    1 lb American - Caramel / Crystal 60L 34 60 7.1%
    1 lb United Kingdom - Chocolate 34 425 7.1%
    1 lb American - Munich - Dark 20L 33 20 7.1%
    1 lb Flaked Barley 32 2.2 7.1%
    1 lb Flaked Oats 33 2.2 7.1%

    Water requirements (gal)
    Mash water needed 8.68
    Grain absorption losses -1.63
    Mash Lauter Tun dead space -0.25
    Amount going into kettle 6.8
    Boil off losses -1.5
    Hops absorption losses -0.05
    Misc. losses -0.25
    Amount going into fermentor 5
    Total: 8.68

    Mash complete: OG 1.059 (8.68 gallons used)
    Pre boil gravity: 1.059 (6.1 gallons collected)
     
  4. LarryBrewer

    LarryBrewer Active Member

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    Hmm.. well the math checks out both at the site and in Kaiser's spreadsheet.

    One place I see a gap is you expected to collect 6.8 gallons in the kettle, but got 6.1. If I add the 1.63 and 0.25, and input that as the mash complete volume I get 114% conversion efficiency (still high).

    The Black Patent ppg is only 27, maybe that is low. That only accounts for 2% if I bring that up to 36.

    What are you using to measure the gravity - a hydrometer or refractrometer? My refractrometer is all over the place unless I calibrate it - very annoying and I pretty much stopped using it. Some are also temperature sensitive, so you can't take a hot droplet of wort and get an accurate reading.

    Beyond that, my guess is there is either a problem with the grain scale, there was a mix up at the home brew store, or volume readings are out of calibration.

    I'd be curious about what gravity readings you got down the line in terms of OG and FG and if those correlate.
     
  5. dstieglitz

    dstieglitz New Member

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    Interesting, I never thought to check the grain bags that came in the box for weight accuracy.

    I have a standard "beginners kit" hydrometer that I use to measure gravity. I'm measuring volume using the old "stick in the kettle" method with a plastic stirrer... I've checked the volume readings against different containers to ensure accuracy.

    At "boil complete" we read 1.072 with 5.3 gallons in the kettle
    At "brew day complete" we read 1.072 with 4.8 gallons in the fermenter.

    It's been in the secondary for several weeks now and today I got a 1.037 (adjusted) reading. I'm using a yeast with 70% attenuation.
     
  6. LarryBrewer

    LarryBrewer Active Member

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    Something is not lining up with the inputs, and it appears we ruled out your hydrometer and volume measurements. That leaves the original grain bill.

    In this case, you will have some high gravity ale there sir! I'd say keep an eye on it next time, and absolutely double check the weights.

    It should be done fermenting after several weeks, really 3 weeks tops and you should be done. Maybe that hydrometer is reading high. What does it read in water?
     
  7. dstieglitz

    dstieglitz New Member

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    Hydrometer reads 1.000 almost on the dot, but our water is decidedly hard here in LA.

    I should add this is a sweet stout, so it was mashed a little hot and was probably a decent amount of un-fermentable sugar in the wort.

    Next time I'll weigh all the grain before mashing and not trust the brew supply place so much.

    Thanks!
     

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