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Old 11-25-2009, 12:18 AM   #1
profarm
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Default Estimated Gravity vs. Actual Final Gravity

Using verious brewing programs you will see an estimated FG and reading recipe books will state the anticipated FG. All grain brewers will mash at differents temps to get a fermentable wort and a OG, and leave the said wort and yeast in fermenter for 7days to 2wks, at temp, to get a desired FG.

How come when I leave my brews in the primary for 7days to 2wks (for regular gravity beers) at most, and my FG is always lower than the projected FG. To get the correct FG do I transfer when the beer reaches the anticipated FG? I thought I was supposed to leave the beer on the yeast to "clean up"...

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Old 11-25-2009, 12:50 AM   #2
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Leave it where it is - the yeast is cleaning up things like undesirable esters and diacetyl, which you don't want in your beer. Even if you transfer the beer off the trub, the yeast is going to do its job, just slower.

If your FG lower than the software's expected FG, then you're getting better than expected attenuation. That's OK - the software is calculating an average, which is part of a range. For example, hopville.com tells me to expect 1.012 for a given recipe, but then in little grey letters below, it prints a range "(1.009-1.014)" to expect. As long as you get somewhere within that range, you're doing fine.

If you get significantly lower, that probably means that you mashed at a lower temperature than you thought, which lead to greater fermentability. Check your mash thermometer - are you sure it's calibrated?

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Old 11-25-2009, 01:02 AM   #3
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Originally Posted by khiddy View Post
If you get significantly lower, that probably means that you mashed at a lower temperature than you thought, which lead to greater fermentability. Check your mash thermometer - are you sure it's calibrated?
Yeah I guess that might be it, but I thought at higher mash temp it is more fermentable? not sure I get lost in all the info I read...

Thanks
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Old 11-25-2009, 01:17 AM   #4
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I usually finish lower than my software suggests. I plan for it. If I want more body I just raise my mash temp. It might be that I am letting my mash sit longer than necessary and extra sugars are being broken down, or it might be that I tend toward the low end on crystal malt. Embrace, accept it as part of your brewhouse numbers and design your recipes accordingly.

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Old 11-25-2009, 01:29 AM   #5
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Mashing at a higher temperature will result in a less fermentable wort, not more fermentable. Unfortunately, there are so many variables in determining attenuation, that forecasts from brewing software (which is unaware of many of these variables) is a bit of a guess. Promash doesn't even bother to guesstimate.
The good news is that if you make a brew that comes out with a particular FG, you should probably get very close to that FG if you repeat the brew using the same ingredients, temperature, and time.

-a.

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Old 11-25-2009, 02:51 AM   #6
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Let the yeast finish the job.

It's possible your thermometer is reading a little high, so your wort is more fermentable than you planned. Just a few degrees off is all it takes.

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Old 11-25-2009, 03:52 AM   #7
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its good if the FG is lower, isnt it? i always like higher ABV! i use BeerSmith, and it likes to tell me I should be happy with 75% eff, but i normally get a little higher. that to me means that I am beating the computer and its always good to beat the computer. up up down down left right left right ba ba select start 30 extra lives! get it done more ABV and higher eff than the computer expects you to get proves that the computer isnt telling me what to do!

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Old 11-25-2009, 03:56 AM   #8
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You could use a different yeast that doesn't attenuate as well.

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Old 11-25-2009, 03:05 PM   #9
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Quote:
Originally Posted by profarm View Post
Yeah I guess that might be it, but I thought at higher mash temp it is more fermentable? not sure I get lost in all the info I read...

Thanks
you have it backwards. lower temperature = more fermentable and lower FG. higher temp = less fermentable and higher FG.
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