Gravity questions

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wcostigan

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I am new to brewing(have only brewed three one gallon batches). I did not have the equipment to measure gravity for my first two batches. On my third, I mashed 1.6 lbs grain in 2.5 qts water. After sparging with 1 gallon, My total wort volume collected was about 1.5 gallons. I used an ATC refractometer and got a reading of 1.033, which is what I was shooting for to end up with a post boil OG of 1.05 at 1 gallon. I collected a full gallon, but my post boil OG was 1.04. Did I somehow boil off some of the sugars?
 

Slow_Day

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It can be difficult to accurately measure pre boil gravity due to the sugars not being equally distributed in the kettle according to some on this forum. I know that I have had similar issues to yours, but not in a 1.5 gallon batch. Did you stir the wort well prior to collecting your sample?
 
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wcostigan

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Slow_Day said:
It can be difficult to accurately measure pre boil gravity due to the sugars not being equally distributed in the kettle according to some on this forum. I know that I have had similar issues to yours, but not in a 1.5 gallon batch. Did you stir the wort well prior to collecting your sample?

I did stir it well and took more than one sample. The refractometer was calibrated, because i tested it with Distilled water before testing. I think I must have had too "hot" a boil going on. Guess I will try a lower boil next time.
 

ianw58

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Unless your boil was so violent that you were splashing wort out of the kettle, you did not "boil off" any sugars.

Something is up with your measurements.

1.5 gallons at 1.033SG is 49.5 points. 49.5 point in 1 gallon yields a post boil gravity of 1.050.

Hence , either your initial reading was to high, your volumes were not correct or your final gravity measurement was too low.
 
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wcostigan

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ianw58 said:
Unless your boil was so violent that you were splashing wort out of the kettle, you did not "boil off" any sugars. Something is up with your measurements. 1.5 gallons at 1.033SG is 49.5 points. 49.5 point in 1 gallon yields a post boil gravity of 1.050. Hence , either your initial reading was to high, your volumes were not correct or your final gravity measurement was too low.

Thank you for verifying that I did the math correctly. The only thing I could do I guess would be to measure exactly my collected wort and post boil wort. I was eyeballing, and I am pretty good at it but I guess I could be off. Would that affect the gravity that much?
 

Slow_Day

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If your gravity numbers are right, you only boiled off 17% of your volume, (i.e. 1.2 pre boil to 1.0 post boil). If your boil was that vigorous for an hour, something is off somewhere with the gravity readings.
 
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