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Old 11-28-2007, 01:36 AM   #1
bobwantbeer
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I'm having issues figuring out exactly when and how to use my hydrometer. I thought readings were to be taken from the carboy right before the yeast is pitched, when racking into secondary, and before bottling/kegging. I've been reading the board though and it seems like many people take readings during the mash and before the boil as well, and I'm confused about exactly which is supposed to be OG and FG and I'm just confused in general. My latest attempt was Bobby's All American Amber listed in the recipe database. The OG is supposed to be 1.052. The reading I took right before I pitched the yeast was 1.035. However, the hydrometer predicted a little under 5%abv which is what it should be in according to the recipe. Did I screw up the beer or not take an OG reading at the apropriate time?

 
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Old 11-28-2007, 01:39 AM   #3
Yuri_Rage
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Start here:

http://www.homebrewtalk.com/wiki/index.php/Hydrometer

and here:

www.howtobrew.com

Great references for a confused brewer.
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Old 11-28-2007, 01:44 AM   #4
bobwantbeer
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All Grain.

 
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Old 11-28-2007, 01:48 AM   #5
Yuri_Rage
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Sorry, I gave you some references when your question was a little more specific than I first thought.

OG is Original Gravity - the hydrometer reading after the boil and before pitching yeast

FG is Final Gravity - the reading after fermentation is complete (usually taken just before bottling, but beer in the bottle/keg should net the same result)

The reason people take pre-boil readings is to determine efficiency and/or to calculate the sparge more accurately.

If you are brewing all grain without this fundamental knowledge (and if you're missing your target OG by 17 points), I might suggest a bit more research and reading before your next batch.
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Old 11-28-2007, 01:50 AM   #6
bobwantbeer
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I just got crappy efficiency then?

 
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Old 11-28-2007, 01:53 AM   #7
Yuri_Rage
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Quote:
Originally Posted by bobwantbeer
I just got crappy efficiency then?
Indeed you did. Really crappy efficiency. Probably less than 50%.
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Old 11-28-2007, 01:56 AM   #8
bobwantbeer
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What's the best way to learn how to calculate and achieve proper efficiency?

 
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Old 11-28-2007, 01:59 AM   #9
bobwantbeer
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I need to learn how to calculate and achieve proper efficiency fast, because my last brew seems to have been a big waste of time.

 
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Old 11-28-2007, 01:59 AM   #10
Yooper
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Well, yeah, it sounds like it if your hydrometer was reading 1.035 and you were expecting 1.052.

BUT, and this is what I do, I know that my efficiency is crappy. So, I just use more grain! And remember, whatever recipe you used is based on the recipe creator's efficiency. So, say I'm making Yuri's recipe and he gets 85% efficiency for an og of 1.050 (just an example!), using 8 pounds base malt. When I make that same exact recipe with my 68% efficiency (at best), my og will be 1.040. Since I know that before I start, I adjust my recipe to use 10 pounds base malt. So, you can find out what your normal efficiency is, and still create any recipe and any og.

Another thing you said- your hydrometer read 1.035 or 5% alcohol. That's not quite accurate. If you were making wine, yes, since it would ferment back to .990.

But that 5% is potential alcohol, not the true amount to expect in your beer. For a true ABV reading, the formula is (OG-FG) x .131. Beer always has unfermentables in it, and should never get below around 1.008 or so. So, if it was 1.035, and it finished at 1.010, the formula would be (35-10) x .131 = 3.28 ABV. A nice session beer!

So the answer to your questions is pretty complex, as you can see! The short answer is to take your sg when you get ready to pitch the yeast, and at the end of fermentation. The hydrometer is useful, though, for checking the runnings of your sparge as well as determining your pre-boil gravity.
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