Strange Gravity Reading.

[Horsepuncher]

I just finished a brew day and had a strange final gravity reading that I can’t Figure out. Maybe one of you has some ideas.

Per Beersmith my I hit my preboil gravity and volume. 1.035, 7.5 gal. At end of boil my gravity was supposed to be 1.047, 5.5 gal. My volume was pretty much exact by my gravity 1.041.

I’m sure my beer will be fine, but why the low gravity? This is the first time something like this has happens.Seems strange especially because the boil off rate was correct.

Thanks for your insight.

 

[bracconiere]

i find for me beersmith 2 , over estimates my og from pre-boil, by 3 points...i've learned to live with it.....

 

[Horsepuncher]

It’s weird. This is the first time this has happened to me. Usually I’m writhing a point.

 

[rsquared]

Is this all grain or extract? If all grain, my only guess is that one of your readings was off.

 

[Horsepuncher]

All grain. I checked my refractometer and the calibration on that is fine. It must be some sort of volume issue. Something in my system must be off. Weird.

 

[Holden Caulfield]

Per Beersmith my I hit my preboil gravity and volume. 1.035, 7.5 gal. At end of boil my gravity was supposed to be 1.047, 5.5 gal. My volume was pretty much exact by my gravity 1.041.

Your measured preboil points = 35*7.5 = 263. Your measured post boil points (not accounting for wort growth to compare accurately) = 41*5.5 = ~225. Points only disappear if you pour off some of your wort.

That said, there is a measurement error in preboil volume or gravity or postboil volume or gravity or any or all of the 4 inputs.

Gravity errors often occur due to not measuring at the calibrated temperature of your instrument. And in the case of a refractometer, not having the preboil wort mixed well enough so a diluted sample gets pulled as only a few drops are needed.

Volume errors occur due to incorrect kettle markings or measurement sticks. Also, not adjusting your wort to room temperature volume will throw off point calculations (only about 2-4%) - boiling wort volume is 4% greater than at room temp and 170 degree wort is about 2% greater than room temperature.

Since you never had this problem before you probably just misread one of your values (brew day is busy) or you pulled a diluted refractometer sample. Been there done that.

Regards,

KB

 

[Horsepuncher]

Your measured preboil points = 35*7.5 = 263. Your measured post boil points (not accounting for wort growth to compare accurately) = 41*5.5 = ~225. Points only disappear if you pour off some of your wort.

That said, there is a measurement error in preboil volume or gravity or postboil volume or gravity or any or all of the 4 inputs.

Gravity errors often occur due to not measuring at the calibrated temperature of your instrument. And in the case of a refractometer, not having the preboil wort mixed well enough so a diluted sample gets pulled as only a few drops are needed.

Volume errors occur due to incorrect kettle markings or measurement sticks. Also, not adjusting your wort to room temperature volume will throw off point calculations (only about 2-4%) - boiling wort volume is 4% greater than at room temp and 170 degree wort is about 2% greater than room temperature.

Since you never had this problem before you probably just misread one of your values (brew day is busy) or you pulled a diluted refractometer sample. Been there done that.

Regards,

KB

This makes sense. Thank you.

 

[rsquared]

Diluted sample is something I hadn't considered for all grain, even though it's why I had asked if this was extract... Stratification due to sparging makes sense, I just forgot probably because I'm usually doing full volume BIAB these days.

 

[Horsepuncher]

It was full volume biab. I think it’s likely that my pre-boil gravity reading was off. Possibly also some mis-reading of volume.