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Thread: Confused on Measuring Specific Gravity

  1. #1
    Join Date
    Apr 2017
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    Cincinnati, Ohio
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    Default Confused on Measuring Specific Gravity

    I am confused on how to calculate specific gravity. I made the following recipe:

    3 lbs Frozen cherries
    3/4 TSP percic Enzyme
    1/4 tsp potassium carbonate
    3/4 tsp DAP (1/4 at start and 1/4 at each sugar break)
    1 1/2 tsp Fermaid K (1/2 at start and 1/2 at each sugar break)
    2.5 lbs Orange Blossom Honey (will add more to step feed)
    Wyeast 1388 smacked for 3 hours

    1. Sanitized everything
    2. Allowed cherries to thaw
    3. Added warm water to bring total to 10 cups at about 90 degrees
    4. Added pectic enzyme and allowed to sit 1 hour per manufacturer instructions
    5. Added 2.5 lbs of honey to bring SG to 1.105 (little over a gallon
    6. Added potassium carbonate, DAP, and Fermaid K
    7. Aerated for 10 minutes with oxygen
    8. Waited till must was 72 degrees and pitched wyeast 1388 that had been smacked for 3 hours
    9. Each day I aerated and degased. 1/3 sugar break is 1.060 and 2/3 is 1.020
    10 my plan is to add 2-3 oz of honey when SG is 1.020 till yeast gives up. with a final SG of 1.025

    Here are my readings with a refractometer
    12 hours 1.095
    1 day 1.085
    1.5 days 1.074
    2 days 1.065 Added DAP and Fermaid K
    3 days 1.051
    The must has been consistently 70-71 degrees.

    This evening while reading the forum I saw that you cannot use a refractometer to measure SG after fermentation starts. I read that I should use a hydrometer, but that I can use a calculation to convert post fermentation measurements using a refractometer to actual SG. I used this site

    https://www.northernbrewer.com/learn...er-calculator/

    Using this site my reading should be:
    12 hours 1.090
    1 day 1.074
    1.5 days 1.056
    2 days 1.042 Added DAP and Fermaid K a little past 1/3 break
    3 days 1.020 2/3 break now

    So . . . . which is right? I am not saying that I do not believe what I have read but I am a little confused and want to make sure I am doing it right. Also is it possible for Wyeast 1388 to go from 1.100 to 1.020 SG in 3 days?

    Thanks for all your help. While my main question is about the SG so I understand what I am doing, I welcome any advice on my recipe.

  2. #2
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    Default

    you cant use refractometer to do gravity readings once fermentation has started.
    Use a hydrometer once fermentation has started.

    In my opinion the calculations are not as accurate as just using a hydrometer

  3. #3
    Join Date
    Apr 2017
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    Default

    OK, when using a hydrometer do I use the reading on the hydrometer or do I need to use a calculator to readjust it after fermentation. Meaning if I put a hydrometer in the mead now and it says 1.030 is that the true reading or is it actually lower.

    Also since I was trying to be extra accurate and thought a refractometer was all I needed that is all I have at the moment. Should I go with the recalculated readings from the web site till I get a hydrometer tomorrow? Meaning and I at my 2/3 sugar break?

    Also does it make sense that Wyeast 1388 made it from 1.100 to 1.020 in 3 days?

  4. #4
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    Quote Originally Posted by Bobubak View Post
    OK, when using a hydrometer do I use the reading on the hydrometer or do I need to use a calculator to readjust it after fermentation. Meaning if I put a hydrometer in the mead now and it says 1.030 is that the true reading or is it actually lower.

    Also since I was trying to be extra accurate and thought a refractometer was all I needed that is all I have at the moment. Should I go with the recalculated readings from the web site till I get a hydrometer tomorrow? Meaning and I at my 2/3 sugar break?

    Also does it make sense that Wyeast 1388 made it from 1.100 to 1.020 in 3 days?
    You can rely on the refractometer reading BEFORE fermentation.
    You can use the calculated adjusted refractometer readings until you get a hydrometer but get one ASAP- this is the only time i reccommend using a LHBS as they are not accurate in their advice and try to get you to buy things that are not the best choice for mead-makers.

    Read the hydrometer as it shows. No adjustment needed.
    Although not likely it is possible as you had it above ideal 68F that it went down that fast. Get the hydrometer reading and that will be your REAL reading.

  5. #5
    Join Date
    Apr 2017
    Location
    Cincinnati, Ohio
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    Default

    Thanks Caduseus I appreciate the advice. I agree that the LHBS does not really give good advice. I have gotten 1000 times more info from here than them.

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