Author Topic: Final Gravity Estimation  (Read 2089 times)

Offline santoch

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Re: Final Gravity Estimation
« Reply #15 on: June 16, 2016, 10:36:43 PM »
I'm with Denny.  It is wort specific.  The wort I make with my thermometers and my water and my starter that mashed at my target temp is going to have different composition than your wort in your mash tun and your water using the same ingredients and temp.  It will yield a different attenuation.

Expectations only put you in the right ballpark.  Repetition is how you know where it will actually land.

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Offline brewinhard

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Re: Final Gravity Estimation
« Reply #16 on: June 17, 2016, 05:59:00 PM »
  Repetition is how you know where it will actually land.

It is the only thing that you can count on providing that all of your measuring equipment is properly calibrated.

Offline Phil_M

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Re: Final Gravity Estimation
« Reply #17 on: June 17, 2016, 06:09:56 PM »
It is the only thing that you can count on providing that all of your measuring equipment is properly calibrated.

I was thinking about that last part yesterday when I transferred one of my beers. To a certain extent, it really doesn't matter if my digital refractometer is off by a little, so long as it's always off by that same amount. So long as you can precisely measure things you can eventually tweak out any accuracy issues as you rebrew and tweak the recipe.

That being said, that digital refractometer was worth every penny. Now that I know that evaporation was all that was throwing my readings off it's been giving the same exact values as my hydrometer, ever single time. Using culture tubes to collect and chill samples eliminates the evaporation while cooling issue, (cooling a sample on a spoon will result in a high reading, due to evaporation.) and makes chilling easy. They're borosilicate glass, so I just run them under cool water for a few seconds. Their volume is so small it takes no time to bring it from boiling to room temperature.
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Offline brewinhard

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Re: Final Gravity Estimation
« Reply #18 on: June 17, 2016, 11:25:17 PM »
It is the only thing that you can count on providing that all of your measuring equipment is properly calibrated.

Using culture tubes to collect and chill samples eliminates the evaporation while cooling issue, (cooling a sample on a spoon will result in a high reading, due to evaporation.) and makes chilling easy. They're borosilicate glass, so I just run them under cool water for a few seconds. Their volume is so small it takes no time to bring it from boiling to room temperature.

Good tip.

Offline Lazy Ant Brewing

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Re: Final Gravity Estimation
« Reply #19 on: June 20, 2016, 10:36:29 AM »
What's worse, I've been gathering data over the past couple years and there are at least two (maybe three, the correlation's weak) yeast phenotypes at play. Not only will two strains likely not attenuate the same wort to the same degree, they may not even exhibit the same *trend* in fermentability as a function of temperature.

More details please on the different phenotypes.  How do you know how many you might possibly have?
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Offline Slowbrew

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Re: Final Gravity Estimation
« Reply #20 on: June 20, 2016, 11:11:20 AM »
It is the only thing that you can count on providing that all of your measuring equipment is properly calibrated.

Using culture tubes to collect and chill samples eliminates the evaporation while cooling issue, (cooling a sample on a spoon will result in a high reading, due to evaporation.) and makes chilling easy. They're borosilicate glass, so I just run them under cool water for a few seconds. Their volume is so small it takes no time to bring it from boiling to room temperature.

Good tip.

I do them same thing with 3cc plastic pipettes.  Pull out 2cc or so, crimp the end of the pipette and run under the faucet or stick the bulb in a snow bank.  Cools it off quickly and doesn't allow evaporation.

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Offline a10t2

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Re: Final Gravity Estimation
« Reply #21 on: June 21, 2016, 03:09:30 AM »
More details please on the different phenotypes.  How do you know how many you might possibly have?

Different temperature/attenuation curves for the different strains.
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