Estimated Gravity vs. Actual Final Gravity - Home Brew Forums

Register Now!
Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Estimated Gravity vs. Actual Final Gravity

Reply
 
Thread Tools
Old 11-25-2009, 01:18 AM   #1
profarm
Recipes 
 
Sep 2008
Angleton, TX
Posts: 89


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"...

Thanks


 
Reply With Quote
Old 11-25-2009, 01:50 AM   #2
khiddy
Recipes 
 
Apr 2009
Portland, OR
Posts: 1,203
Liked 5 Times on 5 Posts


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?
__________________
Beeritas Vos Liberabit Brewing
Primaries: BEER Beer (4/8/12); Fisher-Price My First Mead (12/20/10)
Kegged: Hairy Patersbier (1/28/12); Dick Beer (2/15/12); Get Yer Goat Maibock (2/22/12)
Bottled: Ye Olde Tyme Holiday Ale (9/26/10); Dick Beer (2/15/12); Candy's Dad's Homebrew (2/27/12)
Apfelweins: Crapfelwein (4/4/12); Apfelweinlager 34/70 (2/26/12)
Kit Wines: Fisher-Price My First Amarone (4/1/12); Rosso Magnifico (4/17/12)
On Deck: Albertus Magnus DIPA

 
Reply With Quote
Old 11-25-2009, 02:02 AM   #3
profarm
Recipes 
 
Sep 2008
Angleton, TX
Posts: 89

Quote:
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

 
Reply With Quote
Old 11-25-2009, 02:17 AM   #4
bbrim
Recipes 
 
Jan 2008
Lincoln, Nebraska
Posts: 886
Liked 42 Times on 37 Posts


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.

 
Reply With Quote
Old 11-25-2009, 02:29 AM   #5
ajf
Senior Member
HBT_LIFETIMESUPPORTER.png
 
ajf's Avatar
Recipes 
 
Oct 2005
Long Island
Posts: 4,646
Liked 105 Times on 99 Posts


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.
__________________
There are only 10 types of people in this world. Those that understand binary, and those that don't.

 
Reply With Quote
Old 11-25-2009, 03:51 AM   #6
david_42
 
david_42's Avatar
Recipes 
 
Oct 2005
Willamina & Oak Grove, Oregon, USA
Posts: 25,593
Liked 151 Times on 142 Posts


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.
__________________
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

 
Reply With Quote
Old 11-25-2009, 04:52 AM   #7
jackson_d
Recipes 
 
Mar 2009
Wicker Park, Chicago IL
Posts: 261
Liked 4 Times on 3 Posts


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!

__________________

Fermenting: 12g Elevated Line California Lager
Kegged: Elevated Line Toast IPA, Founder's Breakfast Stout Clone, Elevated Line Blonde, Elevated Line Christmas Molasses Porter
On Deck: Death by Dunkel, Mango Lambic?, Barleywine, Wheat, Cali Lager, Pilsner, Honey Porter, etc., etc...

 
Reply With Quote
Old 11-25-2009, 04:56 AM   #8
BarleyWater
 
BarleyWater's Avatar
Recipes 
 
Jan 2007
Armpit of Dallas (Irving), TX
Posts: 2,204
Liked 23 Times on 17 Posts


You could use a different yeast that doesn't attenuate as well.
__________________

Fermenting: Nada
On Tap:Cran Wit, Dr Pepper Dubbel, Cascadian Pale Ale, Dark Chocolate Stout, Imperial Stout, Brown Mild, Schwarzbier
On Board: IIPA


www.franconiabrewing.com

 
Reply With Quote
Old 11-25-2009, 04:05 PM   #9
RBlagojevich
Recipes 
 
Dec 2008
Posts: 120


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.

 
Reply With Quote


Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Final Gravity Champurrado Fermentation & Yeast 2 10-28-2009 12:32 AM
I have hit my estimated final gravity BillTheSlink Beginners Beer Brewing Forum 5 04-28-2009 12:45 AM
What is a final gravity anyway!? underwaterdan Beginners Beer Brewing Forum 1 01-06-2009 06:09 PM
Actual starting gravity significantly higher than kit's numbers Quikfeet509 Beginners Beer Brewing Forum 19 09-23-2008 12:07 PM
IBU Calculator Actual Gravity goswell Beginners Beer Brewing Forum 6 02-07-2008 06:24 PM


Forum Jump