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Old 10-10-2012, 02:44 PM   #1
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Default Gravity Readings

As a new brewer, I've done about two brews, but never really paid attention to gravity readings. I've just been trying to get the bare-bones of the process down to this point. Now, I'm ready to get more technical, and get better brewing results. My question is, at what point during the brewing process do I take an original gravity reading and final gravity reading? Are there other points during the process I should be taking readings also? Any advice is much appreciated! Thank you!

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Old 10-10-2012, 02:48 PM   #2
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You take the OG reading after thoroughly mixing wort & top off water & aerating. But before pitching yeast. Then wait till the 2 week mark,& test again to see how close to FG you are. Some even wait 3 weeks to take an FG reading. When the numbers are the same 2 days apart,it's ready to package.
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Old 10-10-2012, 02:49 PM   #3
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In all honesty, taking gravity readings should have been apart of your initial process. But to answer your question, you can take an OG reading after your boil process and when it's cooled. You'll want to take it before pitching the yeast. For FG you'll want to wait a few weeks after pitching the yeast, take a reading between 14 and 21 days, wait two to three days and take another. If it remains constant, the beer is done.

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Old 10-10-2012, 02:50 PM   #4
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I try to take readings as close to the temp my hydrometer is calibrated to as possible (60f). I am around that point after adding cold water to my cooled boil, so I take it then, right after pitching yeast. I mostly have been trying to hold that temperature for fermenting, so I take another reading when I think it is getting close to done fermenting or completely done. Then I check again after a few days to ensure it is stable and then bottle.

Feel free to check more to see how fermentation is progressing, but I don't think any more are necessary.

And it isn't a problem to check at temperatures other than where your hydrometer is calibrated, you just have to make an adjustment to your reading based on the temperature.

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Old 10-10-2012, 02:51 PM   #5
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Quote:
Originally Posted by unionrdr
You take the OG reading after thoroughly mixing wort & top off water & aerating. But before pitching yeast. Then wait till the 2 week mark,& test again to see how close to FG you are. Some even wait 3 weeks to take an FG reading. When the numbers are the same 2 days apart,it's ready to package.
Before pitching? Oops...

Is there a reason for that? Learn something new every day...
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Old 10-10-2012, 02:55 PM   #6
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Well,the yeast would ad to the gravity I think. It's also a good practice to do it before pitching,as most will pitch & seal it up straight away. Then remember later that they didn't take an OG reading.
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Old 10-10-2012, 03:17 PM   #7
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Good call. I guess I figured that since the yeast will be in for final gravity measurements, I should do OG measurements with it present as well.

As far as practical measurements go, how critical is it to do it one way or the other? The only thing it will affect is the calculation of ABV, correct? Anyone have an idea how far off the ABV calc will be?

As long as one is consistent batch to batch, is it something to worry about?

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Old 10-10-2012, 03:21 PM   #8
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I take a sample right before pitching yeast. Then I take a sample after about a week. Then another a day before bottling. This way I can compare the gravities after about a week (which for most beers is enough time to fully ferment) and after it's cleaned up. Knowing they are they same assures that the fermentation is complete and that you won't get bottle bombs!

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Good call. I guess I figured that since the yeast will be in for final gravity measurements, I should do OG measurements with it present as well.

As far as practical measurements go, how critical is it to do it one way or the other? The only thing it will affect is the calculation of ABV, correct? Anyone have an idea how far off the ABV calc will be?

As long as one is consistent batch to batch, is it something to worry about?
The ABV part of the scale should be ignored for beer purposes. But, if you did make note of where this was before your beer started fermenting, take out your hydrometer and look at the specific gravity that corresponds to that same level of "ABV." That would be your OG.
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Old 10-10-2012, 03:23 PM   #9
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It's just excepted practice to get a more accurate OG reading before the pitch. Later on,while it is present,there's less sugar,having been converted to alcohol. Alcohol is lighter than the sugars,so the specific gravity reads lighter.
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Old 10-10-2012, 04:16 PM   #10
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Thanks.

I guess what I am trying to ask is this. Since I use my hydrometer primarily to ensure I have a steady FG, pre- or post-pitch doesn't matter, correct?

Where it does matter is in the CALCULATION of ABV (based on OG-FG), correct? (JordanThomas, I think you misunderstood because I am only reading gravitates, not ABV directly.)

I guess what I am really wondering is how do I get the most accurate numbers for my ABV calculation? What complicates this is that the amount of yeast in suspension changes as the beer ferments.

Maybe I should ask this: when fermentation is complete, how much yeast is in suspension and how does this compare to the values of yeast in suspension pre- and post-pitch (ie. 250M cells and end of fermentation is closer to zero than to 1B cells at pitch, so pre-pitch is more accurate)? Have I taken this too far? Thanks again, everybody. Sorry if I have hijacked the thread.

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