Testing Gravity

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Jonnymack123

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I have a lot of questions because I not only worry about every little detail pertaining to everything, but I'm also new to homebrewing (i.e. I haven't attempted it yet, but I'm getting ready to). How do you test the gravity of a beer in the primary fermentation vessel without introducing oxygen to the system? Or do you just pop of the air lock/cork, test it, and then allow the yeast to "push" the oxygen back out? Do you guys just test it after the primary fermentation appears complete or do you test it earlier on and more often? Is it okay to dump the tested beer back into the fermentation vessel assuming that the devices used to test the gravity were sanitized? Also, the gravity of the beer should be near its final gravity when you move it to secondary fermentation correct? I hope all of these questions make sense... THANKS! :D
 
Just sanitize and rack out a sample. Get your reading and go from there. I would make sure gravity reading is stabilized for 2-3 days before transferring. As far as oxygen you will introduce so little it's a non issue. This hobby is no where that scientific to worry about small amounts of oxygen. People frequently "swirl" their wort to stir up the yeast a little to ensure fermentation is complete prior to transferring
 
I just pop the lock briefly and take a sample with a sanitized wine thief. I do this as infrequently as possible, but as often as necessary. The goal is to minimize oxygen exposure but you are unlikely to ever eliminate it completely.
 
Oh and you *can* return the sample to the fermenter but most will advise not to. That small sample is a small price to pay to reduce risk of infection.
 
If you do not stir things up getting a sample for a gravity test is not a problem. There is a layer of co2 over the wort.

I wait 3-4 weeks then take final gravity samples. Often I only take one on the day that I bottle. If it is what I expect for a final I assume it is good.

Never put your sample back into the fermenter. It is not worth the risk for about 3 ounces.

I rarely do secondaries anymore but, yes wait for the fermentation to finish before transfer.
 
As long as the vessel you take the sample with,(& the hydrometer & tube) have been cleaned & sanitized you can safely return it to the fermenter. I only do that with the OG sample,since it's just sweet un-fermented wort. But when taking FG samples starting at 2 weeks,I record the Gravity number & taste the sample to see how it's doing. Also when I get a stable FG 2 days apart. That gives an idea how clear it is,& if it tastes good to bottle.
But I usually give it 3-7 days after FG to clean up & settle out more.
 
I take a sample before bottling and agree that it's better to drink it than toss it back in anyway. I like to know what the beer is tasting like. And like the others, it's not worth the risk of infection and it's more fun to taste the fruits of your labor. Don't worry so much, just get brewing! You'll learn techniques as you go. It's a fun process when you dig right in instead of reading about it and studying it. Good luck and enjoy!
 
Unless I have some reason to rack to a "secondary," such as bulk aging, dry hopping, or freeing up a fermenter, I just leave my beer alone for four weeks. I'll check the gravity a few days before I intend to bottle then again on bottling day to ensure they're the same. I've never been in a situation where I've felt the need to have a beer ready by a certain day. The bottom line is that, unless you're very interested in how quickly your beer is fermenting, you can just leave it alone for a few weeks before checking FG.

Waiting is difficult when you've just started brewing. Patience is one of those virtues you develop after you gain some confidence and understand that your role is to give the yeast the best possible conditions in which to work. After that, it's just a matter of sitting back and letting them do their job. The brewing process is much more enjoyable when you reach this state. The beer is usually better too.
 
I keep an eye on it and if the bubbler hasn't moved in a couple days I bottle it
 
From everything I've read bubling does help to indicate fermentation but some brews just don't get that active. I would recommend using the hydrometer after a few weeks to test for FG. Better than ending up with a bottle bomb because fermentation was "thought" to be over.
 
Don't worry so much, just get brewing! You'll learn techniques as you go. It's a fun process when you dig right in instead of reading about it and studying it. Good luck and enjoy!

+1 - You want to do some research before starting, but there's a point you just have to do it. It will all make more sense then.
 
Actually,that's quite true. I for one just read the steps enough to get down to it. Then got on here for some "field research".
 
Also, in the "FAQ - please read..." sticky there is a great post called "when to go from Primary to Secondary (if at all)" that has some great info. I was actually hopping on this morning to read it again as my first batch is 10 days into fermentation and I was going to check my SG today.

:mug:
 
I have a lot of questions because I not only worry about every little detail pertaining to everything, but I'm also new to homebrewing (i.e. I haven't attempted it yet, but I'm getting ready to). How do you test the gravity of a beer in the primary fermentation vessel without introducing oxygen to the system? Or do you just pop of the air lock/cork, test it, and then allow the yeast to "push" the oxygen back out? Do you guys just test it after the primary fermentation appears complete or do you test it earlier on and more often? Is it okay to dump the tested beer back into the fermentation vessel assuming that the devices used to test the gravity were sanitized? Also, the gravity of the beer should be near its final gravity when you move it to secondary fermentation correct? I hope all of these questions make sense... THANKS! :D

No need to worry about opening up your fermenter to take readings. I know that the air-tight lid w/ gasket and that crazy little airlock device give the impression that the goal is to keep your wort away from ALL exposure to air from the moment you push down on the lid until everything is "done" happening and it's bottling day. But it's misleading. Exposing the wort to the air to take readings is not only ok, but good practice. Just be careful... you'll be tempted to lean over and take a hearty whiff and maybe your wife/GF will want to as well... make sure you don't drop sweater lint from your head or something in the bucket and make sure your wife doesn't let her hair fall down into it. Don't laugh, it's easily done! My preferred reading method for my fermenter bucket is a simple turkey baster to withdraw a sample and my hydrometer in tube. Basically here's what I do:

Make up some sanitizer in a pot - I use a 2 min soak one. I fill my baster with it and let it sink down so the outside contacts the solution too. I also fill my hydrometer tube(not because I will return the wort, but because I'm about to drink from this tube) While it's sitting, I go to my bucket and carefully loosen the lid all around. I always wipe down the lid top first, JUST in case ;). I move the bucket to an open area - ie, I ferment in a closet with a shelf above the bucket... I move it out into the open JUST in case something falls like dust or lint. Then I go get my baster. I carefully take the sample from around the middle depth of the wort, put the lid back on, and bring the sample to the kitchen to put it into my tube. I stick my hydrometer in, spin it a bit to make sure it isn't clinging, and read it. I write down the gravity. I then Take out the hydrometer and stick in my thermometer. I wait for it to settle for a min or so and take the temp and write that down too. Then, providing the sample is being taken after a few days or more of fermentation, I drink the sample wort. I then adjust my gravity reading to the temperature with the formula/calculator and Clean up and I'm done!

Don't rely on the airlock to tell you when your fermentation is done. As others have said, so many variables will affect this and a still airlock is an indication of a still airlock and nothing more! When you THINK the fermentation is done, take a gravity reading and wait a couple days. Take another right before bottling to make sure it hasn't changed, then you know it's bottle time!
 
When you do start your first brew. Order your next ingredient kit and another fermentation vessel. If not you will probably run out of your first batch before the second is ready. Especially if you have friends helping you to deplete your stock.

It is great to go to the fridge and have several choices of your own making.
 
Thanks guys! I wasn't expecting so many nice replies within 24 hours. I feel like I have a good grasp on the general process since I am finishing my major in biology and have done a good bit of research, but some of the terminology still throws me. I'm assuming FG means final gravity, but what does SG mean? Any other abreviations I should know about? :eek:
 
SG is Specific Gravity,the generic term for the weight of the liquid tested. OG is Original gravity,or the gravity before pitching yeast.
Volumes of co2 is just another way of saying how many atmospheres pressure is calculated to be created by the priming sugar converting into co2 & a very small amount of additional alcohol.
 
All my fermenters have bottling bucket spigots on them. Easy peasy to take samples.

I talked to a guy at my local home brewer store, and he was highly against using a bottling bucket as a fermenter (the kit I purchased came with a bottling bucket that was advertised as a fermenter and a carboy).. you've had decent results with yours?
 
I don't take sample tests. Just wait 3 weeks then bottle. The sample goes into the bottling bucket as everything that touches it has been in StarSan. I just take that last reading to calculate the ABV.
 
welker85 said:
I talked to a guy at my local home brewer store, and he was highly against using a bottling bucket as a fermenter (the kit I purchased came with a bottling bucket that was advertised as a fermenter and a carboy).. you've had decent results with yours?

I use my spigot to take samples from my primary and to transfer the beer. Never had an issue with contamination, I just make sure I take apart the spigot, clean it, sanitize it before using the fermenter each time. The liquid doesn't go back into the fermenter once its out and by the time you transfer the beer, the alcohol can usually take care of any small contaminates assuming you don't have some crazy mold growing in there.
 
Is there an average final gravity? I always forget to take the original gravity measure, so I assume there is no point taking a final. But after reading this I'm wondering if, since I'm brewing extract recipes, there is some way to calculate what the FG should be when fermentation is done.
 
If the recipe lists the OG & FG (usually as estimates), then you can use those numbers to get an estimated ABV%.
 
Is there an average final gravity? I always forget to take the original gravity measure, so I assume there is no point taking a final. But after reading this I'm wondering if, since I'm brewing extract recipes, there is some way to calculate what the FG should be when fermentation is done.

IMO it's still worth it to take a reading, just to see. For example, if you do the reading after 2-3 weeks and you see 1.030 on a basic 5.5ish %ABV pale ale, that says the fermentation probably stalled out for some reason. On the other hand if the reading is 1.010 or so after 2-3 weeks, then you can be reasonably certain that it's done.

I suppose if you see a krausen ring in the fermentor 2-3 inches above the beer, that is evidence enough, but for the small effort and cost of the sample, why not just do it.
 
So, I brewed a 3 gallon IPA With 4 lbs extra light DME and 2.4 ounces of citra hops. I did not take the OG but the FG tonight was 1.010. Would this be considered finished or should I wait and do another reading?
 
So, I brewed a 3 gallon IPA With 4 lbs extra light DME and 2.4 ounces of citra hops. I did not take the OG but the FG tonight was 1.010. Would this be considered finished or should I wait and do another reading?


This would have put you with an OG of around 1.059 and an ABV of 6.6%. It should be done. You can wait a day or two and do another reading of you like. I would feel safe throwing it in a bottle at that FG.
 
Ok, so, maybe stupid question; sanitize your hydro and then just test fg in the actual fermenter? As in, in the 5 gallon bucket. That is, if you don't mind not tasting the fg sample? At least that's how I've done it prior to bottling.
 
I use a glass vessle and take enough out to fill a test tube. Since the vessle has a narrow neck I use a turkey Baster. With a bucket you could use a santitized measuring cup and fill a tube to test the FG. As far as I know testing in the bucket will give you a false reading.
 
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