Using gravity sample to see if fermentation is done

[WDT]

Ok, so I pulled a gravity sample of a actively fermenting batch of 1.087 IIPA. I pulled it out a few days ago, ive been watching the gravity drop every day for the past 4 days from 1.029 the first day, 1.024, 1.017 now after 4 days.

If the sample stops do you think the batch has stopped? I mean I could check but this would be a nifty way to monitor the ferment without disturbing the bulk of the batch. I'm of course going to check when the main batch is done.

 

[firemostale]

Cool idea! I am by no means an expert, but I would assume this would work. How are you keeping your sample sanitary?

 

[WDT]

I just dunked both the sample tube and hydrometer in starsan, I've left it uncovered on the counter. I'm not worried about it this time because of the alcohol content (about 9% at the moment).

 

[ChshreCat]

The problem is that the small sample will ferment at a different rate than the 5 gallon carboy. The plus is that the sample should finish at about the same SG as your sample. So when the sample stops fermenting, start checking the fermenter and watch for when it reaches about the same SG and stabilizes.

 

[dannyhawkins]

Also leaving the sample uncovered will allow other wild yeasts to enter. These wild yeasts are coincidentally adapted to ferment a wider swath of sugars so it may continue down to or past 1.000. So to continue this experiment you should add a bung and airlock if possible. (Before leaving it sit a few days)
Ingenious observation though!

 

[WDT]

Thanks! I will probably pull another sample and cover with foil just to control that variable a little better.

I will report back what the sample and batch end up with. I have a feeling it'll be done this week.

 

[homebrewdad]

I've seen this tried before, and it's just not reliable. Temperature can fluctuate way more in a small sample than it can in the full batch. Fermentation speed just won't be the same for sure.

 

[WDT]

I've seen this tried before, and it's just not reliable. Temperature can fluctuate way more in a small sample than it can in the full batch. Fermentation speed just won't be the same for sure.

I'm wondering if they will end up the same FG at this point. Since it is a mini version of what i'm fermenting at the moment. I didn't take temp into consideration, however I do have both the batch and sample holding at about 70* ambient now to clean up fermentation.

 

[HolyKrausenBatman]

A variation of this is referred to as a Forced Fermentation Test. In this test, the sample is kept at a higher temperature than the main batch (say, 80 F or something). The higher temperature sample, in addition to finishing fermentation faster will also give you the maximum attenuation for the yeast/wort combo you just produced. Helpful if you end up with a stuck fermentation, as you will know if raising the temp and rousing the yeast will have any impact or if you had a mash problem. I like this test for any new recipe I brew so I'm not constantly wondering if it is done or not. The main batch will finish higher than the forced sample for a normal fermentation, but in my experience, for most beers this is within a couple of points.

 

[WDT]

Cool, I think my sample finished out at 1.011. It's been sitting there for a couple days now. WL001 is a beast if you let it be. Like 87% attenuation.... wow.

 

[WDT]

If anyone is interested, the sample wasn't done when I posted last. It eventually dropped down to 1.009 and went crystal clear. The main batch dropped down to 1.010. I will test again with different yeast to see if this will be an accurate way to know what final gravity will be.

 

[Revvy]

It's been around, and shot down for years.

It a will only tell you WHAT YOUR BEER WILL FINISH AT, NOT when your 5 gallon batch of beer will be done.

It's used to measure attenuation of the yeast, not rate of fermentation.

It will take yeast a lot less time to chew through 12 ounces of wort than it will 5 gallons.....so don't trust that silly thing that someone came up with because they are too afraid to take samples from their beer as being accurate.

If you do take that as "gospel" you more than likely are rushing your beer off the yeast way to soon. You know "bottle Bombs" or suddenly posting an "is my beer in secondary ruined?" thread because now that you moved it to secondary because the "satellite" said it was done, you now have this scary looking growth that you have never seen in your bucket (because the lid is one) that suddenly grew on top of your wort and is ugly as sin....which we of course will tell you to rdwhahb because that is just krausen and it formed because you racked too soon and the yeast is still trying to work to make beer for you.

The idea came from commercial breweries, but you have to realize when they are using in it a 3 or 7 or 10bbl fermentaion setup, that their sattelite looks like this.

And they are drawing off hydro sample out of that bucket just like we do.

And they are STILL going to be taking readings and tasting the REAL beer in the ACTUAL FERMENTER, before making any determination.

It's been adopted by some home brewers, and unfortunately gets perpetuated by people (mostly noobs scared of taking real hydro readings) but it's about as accurate as airlock bubbling, (and you know where I count that in terms of fermentation gauges- slightly below the astrological calender )

Please don't fear taking a real hydro sample of your beer, don't ever go by a satellite grav reading.....Or an airlock....

Just take your grav reading and be done with it. And drink your samples.

 

[WDT]

Of course, Standard practice is taking gravity samples towards the end of fermentation. Just this time I took one very early in the ferment and happen to leave my sample out a day or two and noticed the gravity had dropped.

The first gravity sample had such a bite to it, tasted like the most bitter grapefruit you could imagine (all cascade hopped IPA fwiw). The last one yesterday tasted pretty amazing. Can't wait to try the final product.