Hitting that FG number, is there a secret to it

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olotti

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What I'm asking after overshooting my FG number on my last couple batches is, is it best to just let the yeast do their thing and where the FG stops it stops or if the target is say 1.014 and I take a sample at day 5 and its at that number is it best to cold crash to keep the gravity stable or is it better to let the yeast finish up even though the number may drop a couple more points? I've used rehydrated 05 and 04 on my last two beers respectively and ended up 2 points low on both FG numbers, I usually check the gravity at day 10 and 14 then I dry hop. Oh I also ferment in my basement where ambient temp is 62-64 so when I cold crash I move the carboy to my upstairs garage fridge where temp is mid 30's. thanks for the thoughts.
 

peterj

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2 points low doesn't really seem like a big deal to me. I'd say that's close enough.

But to answer your question: No, I would definitely not stall the beer on purpose before it has finished fermenting. You should let the yeast do what it's going to do and try to control the FG on the front end with mash temperature, grain bill, and yeast strain choice. Stopping fermentation early can lead to a number of problems. If you bottle carbonate, then once you warm it up again the yeast is going to eat those sugars that are left in there plus the priming sugar so you'll still end up with a lower FG plus overcarbonated beer. Also stopping fermentation early will lead to off flavors because you're not giving the yeast a chance to clean up the byproducts of fermentation which it does after it has gone through all of the fermentable sugars in the wort.
 

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Others may disagree with me, but 2 points is within my measuring error and I wouldn't even consider it different until it was 5-6 points off.
 

ncbrewer

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If you bottle carbonate, then once you warm it up again the yeast is going to eat those sugars that are left in there plus the priming sugar so you'll still end up with a lower FG plus overcarbonated beer.
You could also get bottle bombs - a safety issue.
 
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olotti

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Others may disagree with me, but 2 points is within my measuring error and I wouldn't even consider it different until it was 5-6 points off.
Ok. the most off I've been was 4 points low but then again my OG was 4 points low because I had to add top off water to get back to 5.5 gal. So the fg coming in 4 points low was actually spot on.
 

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What I'm asking after overshooting my FG number on my last couple batches is, is it best to just let the yeast do their thing and where the FG stops it stops or if the target is say 1.014 and I take a sample at day 5 and its at that number is it best to cold crash to keep the gravity stable or is it better to let the yeast finish up even though the number may drop a couple more points? I've used rehydrated 05 and 04 on my last two beers respectively and ended up 2 points low on both FG numbers, I usually check the gravity at day 10 and 14 then I dry hop. Oh I also ferment in my basement where ambient temp is 62-64 so when I cold crash I move the carboy to my upstairs garage fridge where temp is mid 30's. thanks for the thoughts.
Well, first consider where your 'target' FG comes from. If it comes from software, for example, it's not even a good guestimate. It is simply a percentage of the OG, which may or may not be close (usually not so much).

If your target FG comes from brewing the same recipe with the same mash temp over and over, then it's actually a realistic FG and you should be within a couple of points assuming all the conditions are the same.
 

catdaddy66

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I don't worry about the FG after pitching the yeast. It's like being on a roller coaster. Once your in all you can do is hold on til it stops! A bit lower than predicted is fine by me, but I would be more concerned with it significantly high.


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eric19312

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Ok. the most off I've been was 4 points low but then again my OG was 4 points low because I had to add top off water to get back to 5.5 gal. So the fg coming in 4 points low was actually spot on.
This isn't quite right. A 1.040 beer that finishes at 1.010 would have apparent attenuation of 75%. A 1.044 beer with the same apparent attenuation would have a FG of 1.011.

So if you started 4 points low and ended 4 points low your beer attenuated more (possibly a lot more) than your recipe expected and you should try to understand why. Maybe it was the health of the yeast due to rehydration or you mashed low etc.
 

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So, let's take a step back here, as it sounds like a couple assumptions are being made above that may or may not hold up. Are you brewing from extract or all grain?

If you're brewing from extract, then you don't have much control over the fermentability of your wort. The freshness of your extract will play a bit of a role - the fresher the better. Yeast choice also plays a role, as some are simply more attenuative than others, and will just get to a lower FG than others. Comparing US05 to S04, for example - typically SU05 is going to get down a couple points lower than S04, given the same wort.

If you're brewing all grain, mash temps - and most importantly, ACCURATE measurement of mash temps, play a huge role here. If your thermometer is even a little bit off, that can make the fermentability of your wort quite unpredictable. I just realized, for instance, on my last brew day that my thermometer is dead accurate at 32F, but it reads boiling temps at 214 or 215 at a few hundred feet above sea level. Basically, I've been mashing 1-3 degrees lower than I thought I was, and as a result, everything's been overattenuating 2 or 3 points.

And in either case, there's always the possibility that your hydrometer isn't calibrated correctly. Float it in some 60F distilled water and see if it measures 1.000. Neither of mine do.
 
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olotti

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This isn't quite right. A 1.040 beer that finishes at 1.010 would have apparent attenuation of 75%. A 1.044 beer with the same apparent attenuation would have a FG of 1.011.

So if you started 4 points low and ended 4 points low your beer attenuated more (possibly a lot more) than your recipe expected and you should try to understand why. Maybe it was the health of the yeast due to rehydration or you mashed low etc.
My target numbers for the original recipe were OG of 1.068 after diluting with top off water I had 1.064. Recipe FG was 1.014 I hit 1.010. I was actually just 1 point low of the OG post boil but I sacrificed some abv for more volume. I mashed at 152 deg which is what the recipe called for.
 

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Ok. the most off I've been was 4 points low but then again my OG was 4 points low because I had to add top off water to get back to 5.5 gal. So the fg coming in 4 points low was actually spot on.
I'm a noob but I thought the idea was to aim for an OG and not a set-in-stone-starting-volume; people doing full boils boil until OG reached, not a particular volume. I myself do partial boils, and extract-with-steeping-grains, and most of my gravity points are determined by the extract anyway.

My biggest issue is reading the stinking hydrometer with these ("you're older than dirt, Daddy, you should expect to have trouble reading those little lines") eyes; and the fact that it twirls the one scale you need to see to the opposite side EVERY TIME. It's like, magic.
 
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olotti

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I'm a noob but I thought the idea was to aim for an OG and not a set-in-stone-starting-volume; people doing full boils boil until OG reached, not a particular volume. I myself do partial boils, and extract-with-steeping-grains, and most of my gravity points are determined by the extract anyway.

My biggest issue is reading the stinking hydrometer with these ("you're older than dirt, Daddy, you should expect to have trouble reading those little lines") eyes; and the fact that it twirls the one scale you need to see to the opposite side EVERY TIME. It's like, magic.
I'm new to all this also. The way I looked at it was you should have (x) OG at (x) Post boil volume. If you have more volume your OG will be lower, less volume and OG will be higher, the trick is to boil off the right amount leaving you with the correct OG, which you'll know if it's gonna be close by the pre boil starting gravity. Again if you start with (x) starting gravity in whatever your preboil volume is then you should hit (x) OG in your desired batch size. I think this is how it's supposed to go.
 
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olotti

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If you're brewing all grain, mash temps - and most importantly, ACCURATE measurement of mash temps, play a huge role here. If your thermometer is even a little bit off, that can make the fermentability of your wort quite unpredictable. I just realized, for instance, on my last brew day that my thermometer is dead accurate at 32F, but it reads boiling temps at 214 or 215 at a few hundred feet above sea level. Basically, I've been mashing 1-3 degrees lower than I thought I was, and as a result, everything's been overattenuating 2 or 3 points.

And in either case, there's always the possibility that your hydrometer isn't calibrated correctly. Float it in some 60F distilled water and see if it measures 1.000. Neither of mine do.
Well I thought I'd try this theory out and my hydrometer is spot on however when I heated up some distilled water to boiling on the stove my thermometer read 210-211 but never hit 212 deg so it's atleast 2 deg off on the low end. So apparently I've been mashing 2 deg lower than I thought so that would put most of my mashes in the 150 range. Could this be a reason for overattenuating? However it's only been the last two batches that went so low on the FG, the previous 3 I hit ALL the numbers including FG but It's good to know now that I need to adjust my mash temps.
 

peterj

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Well I thought I'd try this theory out and my hydrometer is spot on however when I heated up some distilled water to boiling on the stove my thermometer read 210-211 but never hit 212 deg so it's atleast 2 deg off on the low end. So apparently I've been mashing 2 deg lower than I thought so that would put most of my mashes in the 150 range. Could this be a reason for overattenuating? However it's only been the last two batches that went so low on the FG, the previous 3 I hit ALL the numbers including FG but It's good to know now that I need to adjust my mash temps.
This isn't it. What elevation are you at? I'm at about 1,060 ft above sea level so my boiling point is only about 210F.

And if your thermometer was reading 2 degrees low then you would be mashing 2 degrees higher than you thought, not lower. So if it read 152 it would actually be 154.
 
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olotti

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This isn't it. What elevation are you at? I'm at about 1,060 ft above sea level so my boiling point is only about 210F.

And if your thermometer was reading 2 degrees low then you would be mashing 2 degrees higher than you thought, not lower. So if it read 152 it would actually be 154.
Well I'm guessing in Michigan Im pretty much at sea level, so wouldn't boiling be 212 in which case my thermometer would be off by a couple degrees. So if that's the case then I need to aim for a mash in and strike temp of 2 deg lower than what I originally had thought. I've been targeting 175 deg to get 152 deg in the MLT, so then now I need to aim for 173 deg to get 150 deg reading mash in which is actually 152 deg.
 

peterj

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The lowest point in michigan is 572 feet above sea level (Lake Erie) and the highest is 1,979 ft. Average is 900 ft. At 572 ft water boils at about 211 F. Just google your town's elevation and then put it into a boiling point elevation calculator (this is the first one that came up on google: http://www.csgnetwork.com/h2oboilcalc.html).

Sounds like your thermometer is calibrated correctly.
 
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olotti

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The lowest point in michigan is 572 feet above sea level (Lake Erie) and the highest is 1,979 ft. Average is 900 ft. At 572 ft water boils at about 211 F. Just google your town's elevation and then put it into a boiling point elevation calculator (this is the first one that came up on google: http://www.csgnetwork.com/h2oboilcalc.html).

Sounds like your thermometer is calibrated correctly.
Ill check this out. Thanks for the input and the link.
 
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