Opening the fermenter to check gravity?

[kokonutz]

So conflicted on this. Can I / Should I open my primary fermenter to test gravity? I've got two very different batches happening right now and I am not clear if the style, gravity , etc matter. Ultimately, I'd like to understand the fermentation process a little more closely, learn the numbers, etc, but I also would hate to ruin my beer. Here's some vitals (if it matters):

3 gal batches
Kolsch style at 15 days

• OG: 1.041

Belgian Triple at 12 days

• OG: 1.078

Got my SANITIZED wine theif at the ready, but still on the edge here

 

[VikeMan]

I see a fermenter with a sampling valve and closed transfer capabilities in your future.

Until then, I'd recommend not opening your fermenters any more than necessary. But if you need/want to get a sample, get in and out quickly and cleanly.

 

[user 263363]

Theres liable to be a few different opinions on this. I personally don't check FG until packaging. It's not 100% true, but if I give a beer 2 weeks it will be done 99% of the time. I see many posts on Reddit and Facebook groups where people say they don't even check FG. I am too curious for that personally, but I do wait until packaging to minimize oxygen exposure.

 

[kokonutz]

i think this is where i go into a tail spin...how can i know it's done fermenting? 3 weeks sounds like it should be done, but one of these beers (the Belgian) is bigger, with added sugar so in my head, i think it may need more time. Hence the question to check or not to...i'm inclined to wait 4 weeks and then just package

 

[Immocles]

I also never pull samples until packaging. I can think of one time where I did very early on because I had such a quick fermentation, I was convinced that it was stopped. But it really was just that quick.

 

[user 263363]

i think this is where i go into a tail spin...how can i know it's done fermenting? 3 weeks sounds like it should be done, but one of these beers (the Belgian) is bigger, with added sugar so in my head, i think it may need more time. Hence the question to check or not to...i'm inclined to wait 4 weeks and then just package

If you are that patient, let them sit for 4 weeks. Big beers don't necessarily take longer to ferment, but they generally taste better after sitting a little longer.

 

[Immocles]

i think this is where i go into a tail spin...how can i know it's done fermenting? 3 weeks sounds like it should be done, but one of these beers (the Belgian) is bigger, with added sugar so in my head, i think it may need more time. Hence the question to check or not to...i'm inclined to wait 4 weeks and then just package

Cant help ya much with that high OG brew. Thats out of my league, for sure. I'm in that category of letting the fermenter sit for 2-3 weeks by preference and ease. But I have packaged a few earlier than that based on watching fermentation. Krausen dropped? anything swirling or churning? is the beer clearing?

 

[VikeMan]

i think this is where i go into a tail spin...how can i know it's done fermenting?

The only way to really know is to measure. Twice (2-3 days apart). Or... you could measure the main batch once, after doing a forced fermentation test on a small sample drawn on your brew day.

But, if every other indication (including taste) supports "done" on your bottling day, and the bottling day gravity sample is very close to what you were expecting, that would be pretty low risk.

 

[wsmith1625]

I have a valve in my fermenter and don't use it to pull samples. My fear is that using it for samples will leave me with an unsanitary valve when I transfer to my keg. I know I can spray it down with StarSan when I'm done, but I'm paranoid about that. I just lift the lid and get in and out as quickly as possible. I really don't know which method is better. Good question!

 

[VikeMan]

I have a valve in my fermenter and don't use it to pull samples. My fear is that using it for samples will leave me with an unsanitary valve when I transfer to my keg. I know I can spray it down with StarSan when I'm done, but I'm paranoid about that.

My conical's sampling valve and racking valve are one in the same. I've never had any issues. Before and after taking a sample, I rinse the inside and outside of the barb with a squirt of star san solution. (I have the barb pointing downward, so the solution inside can run off.)

Look at it like this... star san solution will sanitize as far as it can penetrate. And where it can't penetrate, neither can bugs.

 

[MikeCo]

I got a Tilt Hydrometer last year and it's a game changer for knowing how fermentation is progressing without taking samples. It's not cheap at $140, but I consider it one of my best homebrewing purchases.

 

[beernutz]

i think this is where i go into a tail spin...how can i know it's done fermenting? 3 weeks sounds like it should be done, but one of these beers (the Belgian) is bigger, with added sugar so in my head, i think it may need more time. Hence the question to check or not to...i'm inclined to wait 4 weeks and then just package

https://tilthydrometer.com/If it really is that important to you a tilt will give you real time temp and gravity readings. You will be shocked at how quickly final gravity is reached on most ales--I was at least.

 

[MikeCo]

You will be shocked at how quickly final gravity is reached on most ales--I was at least.

I was surprised by this too. I was also surprised how some yeast strains, like Belgian and Saison strains, will ferment most of the sugars very quickly, but then take a couple weeks for the final 10 points.

 

[Brewsncrabs]

If you have to open your ferm vessel to check gravity and expose it to oxygen, then don’t do it. Let it ride. Wait until packaging. What it finishes at is what it finishes at. Don’t sweat it.
Now, if you have a sampling valve, check away. But since you state wine thief, don’t check. Be patient. Or you could ruin your beer.

 

[bwible]

Just an observation here - you have a Belgian and a Kolsch. Very different beers. Kolsch is a “clean” beer. If you want to use your sanitized thief to take gravity readings, I’d probably measure the Kolsch first with a well sanitized thief and measure the Belgian second to avoid any cross contamination. I’d be way more concerned over cross contamination than oxygen. Personally, I don’t do Belgians but to each his own.

 

[smata67]

I will be decisive here and tell you exactly what you need to do now. And that is NOTHING. Wait until Day 21 of fermentation on the Kolsch. Be prepared to bottle. Pop the lid and measure FG. If it is a reasonable value, lets say 1.010-1.015..... IT'S DONE! Bottle away.

Same day, pop the lid on the Belgian and take a FG. It is hopefully somewhere between 1.010 and 1.020. If an extract beer, could be somewhat higher. If so, it is most likely finished, but WAIT! Maybe not. Seal it up and take another measure 3 days later. If it is the same as the previous measure, BOTTLE IT UP!

If the FGs are not somewhat near the expected values I list above, then come back.

 

[YaleH]

What about if you purge CO2 through the air lock grommet while you lift the lid just enough to get what you need done.... that way way it will be a positive pressure at your opening and will limit, if not stop oxygen from getting in.

 

[BrewnWKopperKat]

how can i know it's done fermenting?

For Fermentis brands of dry yeast, there is a "Tips and Tricks" brochure (p 28) which includes these charts:

So each strain of yeast appears to have a different typical schedule. Other yeast providers may provide similar information. But if that information isn't available, consider looking into a Tilt.

So it appears that while "yeast doesn't have a schedule", individual yeast strains, under typical situations may have a schedule.

There's a suggestion that one could initially brew with just a small number of yeast ("https://beerandbrewing.com/fewer-yeasts-better-beer/") with the idea that one gets to know those specific strains well.


addition (7/7): 13.5° is OG 55 and 18° is OG 74 (link)

 

[mattdee1]

I guess if you're eventually going to open your fermentor anyway and let it sit wide-open to the air while you transfer your beer to kegs or bottling bucket, then doing a quick in-and-out to check gravity isn't going to matter much. I mean, sanitizing a thief isn't rocket science.

But if you're actively trying to minimize oxygen exposure (closed transfers during packaging, etc.) then opening the fermentor to check gravity is a poor choice, because you're undoing all of your effort in avoiding oxygen, and worst of all, it's just not necessary. If you must check FG, you can do it at packaging time.

At least for ales, if the following conditions are met, then you can pretty much take it to the bank that the beer is at FG:

- you can see evidence of krausen having risen and fallen
- you have half-decent yeast handling practices
- it has been at least 10 days** in a temperature controlled environment

** some yeasts are slower than others. The idea is you get to know how long it takes after using it a few times. If you really want to be careful, add a few more days, or weeks if you must. But there is no reason to leave beers sitting in fermentors for extended periods of time after they're done fermenting. All you're doing is occupying your equipment at that point, IMO. The beer can "condition" in the keg or bottle.

If the above conditions are met, and your FG check before packaging closely matches what you were expecting, then that should seal the deal.

 

[dwhite60]

Two weeks in the fermenter and it's done.

It's been a long time since I checked gravity before bottling day. If I did have a higher than expected reading I'd then put the lid on and let it sit another week.

 

[ncbrewer]

The Fermentis graphs that BrewnWKopperKat posted show US-05 still fermenting just a little at 15 days. And there are few, but some, fermentations that are slower than typical. I favor two gravity checks 2 - 3 days apart for beer that will be bottled, to avoid bottle bombs.

 

[BrewnWKopperKat]

The two charts (13.5° is OG 55 and 18° is OG 74 [link]) would appear to support the idea of giving "bigger" beers some additional time.

And for those who want to ferment at "ambient" temperature with no or minimal temperature control, a slower working yeast (like US-05) may work better than a faster working yeast (like S-04).

 

[Dland]

So conflicted on this. Can I / Should I open my primary fermenter to test gravity?

If you have a way to do it without exposing to oxygen, sure, if you have a PV you can slightly pressurize w CO2 and push sample out.

If you have to open whole the fermentor to sample, I'd say no. You will oxidize the beer.

I would think one could figure to have low pressure CO2 going into almost any vessel, and have an up tube where one could take a sample, with just a two hole bung.