Testing Final Gravity

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Scoper50
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Testing Final Gravity

Post by Scoper50 »

In my small one and two gallon batches I never bothered to take samples with my hydrometer because I didn't want to waste the beer. But I have my first 5 gallon batch thats supposed to be finished in the fermenter tomorrow and I'd like to test it to make sure fermentation is complete. The problem is I don't know what I'm looking for. It is a Bavarian Hefeweizen and the OG came out at 1.060. When I take a reading tomorrow, what numbers should I be looking for?
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Re: Testing Final Gravity

Post by Beer-lord »

Scoper, the instructions for your recipe should give you a range that you should look for in a final gravity. What exact kit did you use? You can go online and look for that info for that recipe and follow that as a guide.
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Re: Testing Final Gravity

Post by RickBeer »

Right.

As a guideline, you're looking for a number ROUGHLY 75% less than the OG. So in your case, ROUGHLY 1.015. Could be 85% less, could be 70% less.

You can also lookup the yeast by Googling it and the manufacturer will give an idea of final attenuation. For example, US-05 by Fermentis should be around 81%. If you're within about 5 points of what they state (in this case 76 - 86% attenuation), and it doesn't change on the 2nd reading (see below), you're usually good.

Ideally, take a reading and then take another reading 48 hours later, and ensure they are unchanged.
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Re: Testing Final Gravity

Post by Dawg LB Steve »

You can pull a sample and keep it in sample tube you can cover it loosely with sanitized foil or wadded up paper towel if it is still fermenting it will let CO2 escape, if its done you won't be opening the fermenter subjecting it to infection and only using one sample. If you let it go 16-18 days generally it will be done and the yeast will have cleaned up after itself from the huge party it just had!

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Re: Testing Final Gravity

Post by Kealia »

Dawg LB Steve wrote:You can pull a sample and keep it in sample tube you can cover it loosely with sanitized foil or wadded up paper towel if it is still fermenting it will let CO2 escape, if its done you won't be opening the fermenter subjecting it to infection and only using one sample. If you let it go 16-18 days generally it will be done and the yeast will have cleaned up after itself from the huge party it just had!

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This is good advice. When I pull samples, I either:
1) Leave it in the hydrometer tube and cover loosely with foil, OR
2) Pour that into a bottle and stuff a napkin the neck like a Molotov Cocktail

Either way, I check it again 48 hours later to see if it has changed. This eliminates the need for pulling multiple samples.
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Re: Testing Final Gravity

Post by ckd022 »

Great idea guys! I never thought of saving the sample and using that same pull for later SG testing. I usually just drank mine! I think I’ll be changing my process on future batches. Thanks for the tip!

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Re: Testing Final Gravity

Post by Scoper50 »

Good advice guys! Thank you
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Re: Testing Final Gravity

Post by FedoraDave »

As a rule of thumb, if your beer has been fermenting for at least 14 days, it should be complete. If you've had a healthy krausen, that is, and all the other indications of normal fermentation were there. I usually let my beers go around 3 weeks before bottling/kegging.

But Rick's advice is sound. I take the last two digits of the OG and divide by 4 to get the projected FG. So if my OG is 1.060, 60 divided by 4 is 15. So anything around 1.016 or under is fine.

As far as wasting a sample, here's what I do to limit and/or mitigate that. I take the OG after I've racked to the carboy and before I pitch the yeast. I sanitize the beer thief inside and out, I sanitize the sample tube, and I sanitize the hydrometer. So I don't have any worries about pouring that wort back into the carboy. In fact, since I mostly use liquid yeast, I use part of that wort to rinse out the yeast container after pitching, and pour it into the carboy, assuring that I'm getting all the yeast I can out of that container.

I don't take a reading until I'm ready to keg or bottle, just to confirm that fermentation is complete and because I like to be able to calculate the ABV of that batch. So I sanitize the beer thief inside and out again, take my sample, get my reading, do my calculations, and then I drink that sample. It gives me an idea of how the beer turned out, and what it's going to be like when it's ready to pour or tap. Even though it's not carbonated, I can still analyze the aroma and taste how the ingredients all blended and it gives me something to look forward to.
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Re: Testing Final Gravity

Post by Banjo-guy »

I bought a Tilt. It’s an expensive device that floats in the wort. I think it was 120.00. That’s definitely a luxury item for me but it’s really great for following fermentation. I can check the gravity from another room if the Bluetooth connection is strong enough. What I love about it is the fact that I never have to open up my fermenter to check gravity.
I guess I’m a high tech brewer.
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Re: Testing Final Gravity

Post by BlackDuck »

I never heard of Tilt...so I looked up it. That is awesome.
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Re: Testing Final Gravity

Post by Banjo-guy »

I love it.
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Re: Testing Final Gravity

Post by Kealia »

Banjo-guy wrote:I bought a Tilt. It’s an expensive device that floats in the wort. I think it was 120.00. That’s definitely a luxury item for me but it’s really great for following fermentation. I can check the gravity from another room if the Bluetooth connection is strong enough. What I love about it is the fact that I never have to open up my fermenter to check gravity.
I guess I’m a high tech brewer.
You should start a thread with screenshots of the app and stuff so we can geek out with you.

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Re: Testing Final Gravity

Post by Banjo-guy »

Kealia wrote:
Banjo-guy wrote:I bought a Tilt. It’s an expensive device that floats in the wort. I think it was 120.00. That’s definitely a luxury item for me but it’s really great for following fermentation. I can check the gravity from another room if the Bluetooth connection is strong enough. What I love about it is the fact that I never have to open up my fermenter to check gravity.
I guess I’m a high tech brewer.
You should start a thread with screenshots of the app and stuff so we can geek out with you.

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I’ll take a screen shot tomorrow and post it.


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Re: Testing Final Gravity

Post by ScrewyBrewer »

Interesting concept. I'd like to geek out as well.
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Re: Testing Final Gravity

Post by Banjo-guy »

How do I post pictures? I’ve totally forgotten how to do it.
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