Alcohol %

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tjstromquist

tjstromquist

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Just moved my dunkelweizen to the secondary fermenter after 10 days. Color looks great, smells awesome and even tastes pretty good! I took a hydrometer reading today after transfering and the alcohol % is only around 2. Will this % increase over the next few weeks in the secondary and bottles or did I do something wrong? This is my first batch by the way.

Thanks!
 
If you're going by the marks on your hydrometer, keep in mind that you subtract the current % from your initial % to get your ABV. ie> If you measured your gravity before any fermentation took place and it sayed 7%, and now it says 2%, that means you have an actual ABV of 5%
 
Being a rookie I didn't take any measurements before fermentation (actually didn't see that mentioned anywhere).
 
What's the recipe? There are some software tools that can guesstimate what the gravity was at the start and maybe figure it out that way. (That's about the only option at this point if you really want to know the alcohol content.)

-walker
 
And if you don't happen to know the quantities involved, don't sweat it and save it for the next batch. I didn't have a hydrometer for my first batch and it came out just fine ;)
 
If it was a kit with a LME or DME extract you'll be very close to within what they stated the ABV would be unless you had less/more water than recipe called for.
 
A hydrometer is an excellent tool though not absolutely necessary. Ideally you should use it at several points in the brewing/fermenting process to really keep tabs on what's going on. I assume you're brewing from extract, in that case it's not as helpful as it would be if you were doing all grain but it will still tell you when to rack to secondary and when to bottle and it'll tell you what your abv is.

To calculate your abv you need to take the initial gravity reading (gravity of wort when you pitch the yeast). In this way you can measure how much denser than water your beer is (the added density is, of course, sugar in one form or another). Initial gravity is usually in the 1.050 - 1.070 range though it can be much higher or lower depending on the beer style (barly wine or imperial stout vs. an english mild). If you put your hydrometer in 60F water it will measure as 1.000 - the density of water at 60F is your effective zero point (even though it's a 1 and not a 0). You compare your beer to this number to figure out abv. When you bottle you take another hydrometer reading and that reading will be significantly lower than the first. The 1.012 range is typically the point the signals the end of fermentation and thus the time to bottle - the exact number depends on beer style/color of extract used. In this case much but not all of the sugar has been transformed into alcohol; because alcohol is less dense than either sugar or water it will effectively lower the density of the beer and bring it close to 1.000 (wines will actually drop below 1.000). So, the higher the initial gravity and the lower the final gravity the more abv you'll end up with. Now, darker extract has more complex sugars that the yeast cannot ferment into alcohol - this left over sugar is what gives darker beers their dense mouthfeel, dark color, and malty taste. So, lighter beers will typically (but not always) be drier and will have a lower final gravity (If you brew from grain the mash temp lets you have a great deal of control over the fermentable vs. unfermentable sugars and thus the final gravity) . To actually transform the gravity readings into abv numbers there are a bunch of free calculators online (google it), and in brewing programs. Of course, you can also look at the abv guage on the the hydrometer at the start and again at the finish, subtract the two numbers and the result is you actual abv. Oh, and make sure to make temperature corrections.. remember the hydrometer is set for liquids at the 60F mark - if your wort/beer is warmer or cooler then you'll need to correct the reading. Your hydrometer should have come with a sheet that contained temp corrections, but there are also free calculators online that will perform this task for you.

I apologize for the lengthy post, hopefully it clarified the "whys" of the process since the "hows" have been addressed.
 
So the only reason to take the 1.000 type reading is to see if it is ready to bottle? If you just want to know how much alcohol you use the other reading?

I go with the bubble method for my racking cue.
 
billybrew said:
So the only reason to take the 1.000 type reading is to see if it is ready to bottle? If you just want to know how much alcohol you use the other reading?

I go with the bubble method for my racking cue.
Click to expand...
The only reason to take the 1.000 reading (putting the hydrometer in 60 degree F water) is to make sure you hydrometer works.
 
You can buy a proofing hydrometer. This will measure the alcohol % not the alcohol potential. This is mostly used for whiskey and the like but it should work for your brew, not positive so you may want to check up on it before spending cash on it.
 
Let me simplify:
To calculate abv you need to know the OG (gravity when you pitch the yeast) and FG (gravity when you bottle). Alternatively the "fool proof" method is to measure the abv at the time you pitch the yeast and the abv at the time you bottle - subtract the two numbers and that's the abv. Of course, that method does not include temperature corrections (which have probably a very minimal effect anyway). As for a 1.000 reading.. you're beer should never read 1.000 (that would be REALLY thin beer).. water will read 1.000 at 60F (that's what the hydrometer is calibrated for, that's the "zero point" so to speak).
 
Lost said:
Let me simplify:
To calculate abv you need to know the OG (gravity when you pitch the yeast) and FG (gravity when you bottle). Alternatively the "fool proof" method is to measure the abv at the time you pitch the yeast and the abv at the time you bottle - subtract the two numbers and that's the abv. Of course, that method does not include temperature corrections (which have probably a very minimal effect anyway). As for a 1.000 reading.. you're beer should never read 1.000 (that would be REALLY thin beer).. water will read 1.000 at 60F (that's what the hydrometer is calibrated for, that's the "zero point" so to speak).
Click to expand...


I'm sorry but that is not the ABV.

Here is a basic formula:

Alcohol percentage by weight equals 76.08 times Original Gravity minus Final Gravity divided by 1.775 minus Original Gravity. It is easier to scribble this down: ABW = 76.08(OG-FG)/(1.775-OG).
 
Charlie Papazian says on page 43 of the Complete Joy of Homebrewing (FSG-OG)105=ABW
ABW.1.25=ABV

I'm sure both ways are correct ScottT, I'm not a math whiz, and you seem to know your stuff, but I thought I'd throw this out there.
 
The specific formula used was 1.040-1.010= .030
.030x105=3.15% by weight.
3.15x1.25=3.94

This is just what Papazian says, and it's the only real book I've read on homebrew.
 
Well, this is going to be a bit complicated to explain so just let me take you to some sources of my info.

This is where I got the above formula: http://www.realbeer.com/library/beerbreak/archives/beerbreak0301.php

"Alcohol percentage by weight equals 76.08 times Original Gravity minus Final Gravity divided by 1.775 minus Original Gravity. It is easier to scribble this down: ABW = 76.08(OG-FG)/(1.775-OG)."

Notice that I gave the formula for ABW not ABV by mistake. That's what I get for posting while distracted at work.

What I didn't post is that to convert ABW to ABV, The formula is this:

ABV = ABW (FG/.794).

Now look here:

http://beeradvocate.com/news/stories_read/518/

"Calculating the ABV
Say our brewer crafted a high-alcohol beer. The OG measured at 1.080, and the beer stopped fermentation with a FG measurement of 1.011. Simply subtract the FG from the OG and multiply by 131.

1.080 - 1.011 = 0.069 x 131 = 9.039%"

So we've got a 9 percent alcohol by volume beer. Easy!"

Now, let's test both ways:

OG 1.050
FG 1.010

Using the first formula from Real Beer for ABW, ABW = 76.08(OG-FG)/(1.775-OG)

76.08(1.050-1.010)/(1.775-1.050)
76.08(.04)/.725
3.0432/.725
ABW = 4.198

Now converting that to ABV, ABV = ABW (FG/.794).

4.198(1.050/.794)
4.198(1.322)
ABV = 5.550


Next, let's use the ABV formula from the other source, beeradvocate
(Beer: OG-FG(131)

1.050-1.010(131)
.04(131)
ABV = 5.24

Mmmmm which is it?

Let's try caluclations from here: http://byo.com/feature/1315.html

"Final Gravity and Alcohol Content
The final gravity of a beer (in gravity points) can be calculated as:

FG = OG (1 - AA)

where OG is original gravity in gravity points and AA is the apparent attenuation as a decimal. Typical ranges of apparent attenuation of different yeast strains are given in the websites of yeast suppliers such as Wyeast and White Labs. (A value of 0.75 for AA gives a decent estimate for most yeast strains.)

Alcohol (ABV, alcohol by volume) can be calculated as:

ABV = (OG - FG) * 0.129

where OG and FG are the original and final gravity of the beer (in GP).

So using these formulas: OG-FG(.129)

1050-1010(.129)
40(.129)
ABV = 5.16

Damn Let's try another, You say Charlie Papaizan says it's:
(FSG-OG)105=ABW
ABW.1.25=ABV

(1.050-1.010)105
(.04)105
ABW = 4.2

4.2(1.25) = ABV
ABV = 5.25

Now given all this data. We've tried 4 different formulas from documented sources to reach an ABV concensious. I'll be danged if there just isn't one.

So what is the ABV for our sample beer that started at 1.050 and ended up at 1.010?

5.25 (Papazian)
5.16 (BYO)
5.24 (beeradvocate)
5.55 (realbeer)

Take your pick. Do you want to brag about how much alcohol you generated? Use realbeer's formulas.

Do you want to convince your wife that you are not consuming as much alcohol as she thinks? Use BYO's formulas.

I really don't know which is the most accurate. I just know what I've learned from my sources and that it is not as simple as just subtracting OG from FG.
 
With a triple scale hydrometer, can't you just take an alcohol % reading of the wort and a reading of the beer prior to bottling and subtract the two? :confused:
 
The Councilman said:
With a triple scale hydrometer, can't you just take an alcohol % reading of the wort and a reading of the beer prior to bottling and subtract the two? :confused:
Click to expand...
You sure can. I think this is what Lost was alluding to. It's effectivly the same as making an OG-FG/C calculation.

I think it's amuzing how many different ways there are to calculate ABV, as every time I see a formula, it's different then the last.
 
LupusUmbrus said:
You sure can. I think this is what Lost was alluding to. It's effectivly the same as making an OG-FG/C calculation.

I think it's amuzing how many different ways there are to calculate ABV, as every time I see a formula, it's different then the last.
Click to expand...
I'm all for making beer brewing easy so that is the method I use. Sometimes I don't even use my hydrometer. I time bubbles for my first racking and keep in the secondary for at least two weeks and bottle the first time I get a chance after 2 weeks have passed.

I hate math and if I had to do it to brew, I probably wouldn't be brewing.

Besides if it's a tasty beer I don't much care what the ABV is. I usually judge by how many I can drink before getting that certain feeling.
 
If you really want to know the final ABV, take 100 ml of your brew (measure the temperature) and gently heat it to 78C (172F). At that point, the alcohol will start boiling off. Watch the temperature closely. As soon as it starts rising again, take the sample off the heat and cool it down to the original temperate. Measure the volume and subtract from 100. Yes, you lose some water in the process, but not much.

You can also freeze an sample and pour off the alcohol, but it's not as accurate due to alcohol getting locked into the ice matrix.

Waste of brew, but there it is.
 
What I do is quaff three of my homebrews while I'm upstairs in the office surfing homebrewtalk.com. I give them 10 minutes to sink in while I dispense helpful advice, then I sprint downstairs as fast as I can. If I only fall down the last 4 steps, I know my abv is ~4%. If I fall down 7 steps, ~7%. 10 steps or more and I classify the beer as "Imperial".

While it's not very scientific, it is highly empirical, and as an added bonus requires no extra equipment other than a flight of stairs and a s.o. that can drive to the ER.
 
Interesting method BG. Good to know that as the number of stairs you fall down increases, you preception of pain possibly stays flat :confused:
 
BeeGee said:
What I do is quaff three of my homebrews while I'm upstairs in the office surfing homebrewtalk.com. I give them 10 minutes to sink in while I dispense helpful advice, then I sprint downstairs as fast as I can. If I only fall down the last 4 steps, I know my abv is ~4%. If I fall down 7 steps, ~7%. 10 steps or more and I classify the beer as "Imperial".

While it's not very scientific, it is highly empirical, and as an added bonus requires no extra equipment other than a flight of stairs and a s.o. that can drive to the ER.
Click to expand...

I hope you're wearing a helmet. :D
 
I read in some book on brewing ( non-committal, huh ?) and a Cooper's brewing kit instruction ,the formula : OG-FG
_______
7.5 + .2 ( for priming sugar) =ABV


There's always the head check. Like Bee Gee , I drink and observe my reactions to determine alcohol content. I live in a one story house , so I can't use the stair method . I drink until I can't feel my head , divide the number of ounces consumed by 9.3876, correct for temp. ( 1% decrease for every 10 degree increase above 68 degrees) , and then say, " Wheee, Doggies ! That shore do got a kick to it ! ". Not as scientific as some, but it works for me.
 
I agree with HB Bill. Any one of these methods gives you basically the same answer, and like BG says, the best way to really tell is by how drunk (i.e. how many stairs you fall down) you are after drinking it. Anyway, if you want to get terribly technical, I don't think there's really any way to accurately determine the ABV after bottling. Of course, someone will prove me wrong on that, but my point is, how much could it matter? It's beer. That's good enough for me.
 
found this on wikipedia explains some things.....

For a given alcoholic beverage, there are two types of gravity measurements, taken before and after fermentation:

Original gravity (OG), which is a measure of the specific gravity of an unfermented beverage. (OG is the "sugar before fermentation" measurement.)
Final gravity (FG), sometimes called Terminal Gravity, which is a measure of the specific gravity of the fermented beverage. (FG is the "sugar after fermentation" measurement.) Typically, FG is measured only once fermentation is completely finished - that is, all of the fermentable sugars have been turned into ethanol.
The difference between OG and FG is a measure of the amount of sugar consumed in the fermentation, and therefore it can be used as a rough, indirect measurement of the alcohol content of the beverage. It is a "rough" measurement of alcohol content for several reasons:

Each yeast has a certain power of attenuation, which is the ability to consume sugars down to trace amounts.
Different beverages have higher or lower proportions of non-fermentable sugars (trisaccharides and longer polysaccharides).
Thus, final gravity is not a simple function of original gravity - that is to say, FG cannot be accurately calculated from OG. However, it is nonetheless a common practice to "design" a beverage based on the theoretical final gravity. This is done by summing the GU/lb of the beverage's various starting materials and dividing by the volume of liquid being fermented. This gives the expected final gravity, but is rarely, if ever, an accurate calculation of actual final gravity. (For example, dry malt extract has approximately 45 GU/lb. If five pounds are used to make two gallons, you have: 45GU/lb x 5lb = 225GU ; 225GU / 2gal = 112.5 GU per gallon, yielding a product with a gravity of 1.1125.)
 
voodoochild7 said:
You can buy a proofing hydrometer. This will measure the alcohol % not the alcohol potential. This is mostly used for whiskey and the like but it should work for your brew, not positive so you may want to check up on it before spending cash on it.
Click to expand...

Proofing hydrometers do not work in beer. The assumption when using a proofing hydrometer is that the liquid contains not sugar, only alcohol and water. Beer nearly always contains significant residual sugars.

Craig
 
Since this thread got bumped....

The correct way to measure alcohol content in beer is gas chromatography. If you do not have a gas chromatograph, you can estimate.

All of the estimations given in this thread assume that alcohol content is a linear function of the change in apparent extract. This will be accurate at one particular alcohol content and less accurate the further you get away from that point. I suspect that some of the approximations I see suggested were developed for wine and work poorly for beer.

The best approximation I have seen was published on HBD by George Fix. I have posted it here a few times so the enterprising google searcher will be able to find it somewhere. It involves first approximating real extract and then using that in a fairly good approximation of ABW.
 

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