I have just started brewing beer and I seem to keep producing very low alcohol content brews. My first brew was a wheat beer from a basic kit. I let it ferment for 1 week and then bottled for 5 weeks. It tastes great, but the hydrometer only read 2%. I also made an IPA to which I added an additional lb of sugar in order to increase the alcohol percentage, but that also came out to 2%. I have used 2 different hydrometers and they are both giving me the same result of 2%. Any ideas of why my beer alcohol content is so low?
Acidental Low Alcohol Content
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Where are you getting "2%"? Is that the reading on the hydrometer before you bottle it? If so, that's not the correct reading. That's the "potential alcohol" scale part of the hydrometer- how much sugar is left in the beer if it all fermented to alcohol. It's not an alcohol meter, to tell you the alcohol percentage.
The way to get your alcohol content requires a tiny bit of math. The formula is OG (original gravity) minus FG (final gravity) and multiply the result by 131.
To do that, you look at the "specific gravity" part of the scale, not the potential alcohol scale. The PA scale is for winemakers, and is not used by beer brewers.
So, say your OG was 1.050. And your FG was 1.010. Then you'd plug your numbers into the formula (1.050-1.010)x 131 = 5.24%.
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I think you are reading your hydrometer incorrectly.
https://www.youtube.com/watch?v=xtQt7HiObuU&feature=youtube_gdata_player
Watch this video, it will help you out some
Edit:
Or you can listen to yooper. I hate being late to the party.
you have to use the OG and FG to calculate the alcohol content. Just reading the side of your hydrometer when you take your FG does not work. Go here to calculate your ABV
If you got your volumes correct it is impossible to mess up your ABV on kits
If you got your volumes correct it is impossible to mess up your ABV on kits
I actually have one more related question. Now that my wheat is bottled and ready to drink and my IPA is bottled and will be ready in 2 weeks, is it possible to determine ABV since I did not take a correct reading at the beginning? Is it possible to figure out from the recipe used what the OG was? Additionally, should I just take the FG at the end of bottling, when they are ready to drink? Some forums suggest letting all of the carbonation go away before measuring FG.
Generally you measure your FG before you add your priming sugar... taking two readings over 3 days lets you know you've actually hit your FG and that you're ready to bottle.
Carbonation can def. mess with a hydrometer, as the bubbles will stick to it. You can spin it around to get the bubbles off and at least give you an idea of what your FG is though, I guess.
With an extract brew, if your volumes were right, your OG will be spot on. The problem is that the FG can vary, depending on the attenuation of the yeast. But if you give us your recipes (including what the OG was supposed to be), and what yeast you used, I'm sure a ballpark figure can be figured out. Or if you measure the gravity of your carbed up beer, it might work as well... though others prob. would know better than me on that.
chawagi
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It would probably all be ballpark figures and assumptions at this point, but you should be able to get relatively close.
You know that you were reading the potential alcohol scale on the hydrometer, so see what the S.G. reading is that matches with the 2% on the PA scale. Then you can assume that you matched the recipe reasonably well by following the instructions which should have given you anywhere from a 1.056-1.075 OG for an American IPA. Go middle of the road and call it a 1.065.
(1.065-whatever S.G. reading matches with the 2% PA) x 131 should roughly be your ABV. Then add roughly an extra 1% ABV for a lb of added sugar in a 5G batch.
Best I can come up with.
woozy
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Think of it this way: The potential alcohol scale is how much potential alcohol is *left* in the brew. A reading of 2% (which is equivalent to 1.015) means that there is enough sugar *left* to up your alcohol 2% (*if* you were to somehow manage to ferment it all).
[Notice the alcohol percentages go *down* not up. When you startee the wort the alcohol scale probably read something like 8% (equivalent to 1.062) potential alcohol (when you *know* there is *no* alcohol in it) and finished at 2% (when you know there is more alcohol than when you started) and if it kept going it could go to 0% if you ever got a s.g. of 1.000.]
The way to use the alcohol scale is to measure the original potential alcohol on brew day, let's say it read 8% (which means that if you converted *all* the sugar to alcohol you'd get something that was 8% alcohol), and to measure the final potential alcohol weeks later, let's say it read 2% (which means that if you converted all the *remaining* sugars, the remaining sugars would contribute alcohol that is 2% of the volume) and subtract the two (so, you had the potential to get an 8% beverage but you but didn't use it all and you are left with enough sugar to make a 2% ABV; that means the sugars that were converted were enough for a 6% ABV).
Basically this is the same thing as subtracting the two gravities and multiplying by 131. The potential alcohol scale is simply the gravity scale offset by one multiplied by 131. (2% => 1.015; .015*131 ~= 2... 8% => 1.061; .061*131 ~= 8. ABV = O.potential alcohol - F.potential alcohol = 8% - 2% = 6% *OR* ABV = (og - fg)* 131 = (1.061 - 1.015)*131 = .046*131 = 6%. Neat, huh?)
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Hmm. Well, you *can* use it. My LHBS guy didn't tell my not to use it. You just subtract the original reading from the final reading. Presto!
However, the scale and margin of error for beer use is so large on the PA that the Gravity scale is much more precise. But I'd use the Gravity scale for wine as well. It's simply that much more precise.
In theory they're the exact[*] same thing only on a different scale.
The important thing to understand is that the PA measures *potential* alcohol (from the sugars remaining) and *not* actual alcohol that currently exists. (Those are actually almost exact opposites).
[*]Oops, I guess I should be careful when I use the term "exact same". Potential Alcohol measures potential alcohol and Gravity scale measures weight of the liquid in relation to the weight of the same volume of water (1.062 means a gallon of wort weighs 1.062 times as much as a gallon of water). These are of course completely different things. When I say they are the "exact same" I mean they are related is such a way that the measurements are proportional and measuring one directly measures the other (by multiplying or dividing by 131).
The third measurement is the Balling or Brix, BTW, and it measures the percentage of sugar by weight and what I find interesting is that it *doesn't* seem to be proportional. 20 on the Brix is *over* 1.080 on the gravity, while 10 on the Brix is *under* 1.040 on the gravity.
[Notice the alcohol percentages go *down* not up. When you startee the wort the alcohol scale probably read something like 8% (equivalent to 1.062) potential alcohol (when you *know* there is *no* alcohol in it) and finished at 2% (when you know there is more alcohol than when you started) and if it kept going it could go to 0% if you ever got a s.g. of 1.000.]
The way to use the alcohol scale is to measure the original potential alcohol on brew day, let's say it read 8% (which means that if you converted *all* the sugar to alcohol you'd get something that was 8% alcohol), and to measure the final potential alcohol weeks later, let's say it read 2% (which means that if you converted all the *remaining* sugars, the remaining sugars would contribute alcohol that is 2% of the volume) and subtract the two (so, you had the potential to get an 8% beverage but you but didn't use it all and you are left with enough sugar to make a 2% ABV; that means the sugars that were converted were enough for a 6% ABV).
Basically this is the same thing as subtracting the two gravities and multiplying by 131. The potential alcohol scale is simply the gravity scale offset by one multiplied by 131. (2% => 1.015; .015*131 ~= 2... 8% => 1.061; .061*131 ~= 8. ABV = O.potential alcohol - F.potential alcohol = 8% - 2% = 6% *OR* ABV = (og - fg)* 131 = (1.061 - 1.015)*131 = .046*131 = 6%. Neat, huh?)
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Hmm. Well, you *can* use it. My LHBS guy didn't tell my not to use it. You just subtract the original reading from the final reading. Presto!
However, the scale and margin of error for beer use is so large on the PA that the Gravity scale is much more precise. But I'd use the Gravity scale for wine as well. It's simply that much more precise.
In theory they're the exact[*] same thing only on a different scale.
The important thing to understand is that the PA measures *potential* alcohol (from the sugars remaining) and *not* actual alcohol that currently exists. (Those are actually almost exact opposites).
[*]Oops, I guess I should be careful when I use the term "exact same". Potential Alcohol measures potential alcohol and Gravity scale measures weight of the liquid in relation to the weight of the same volume of water (1.062 means a gallon of wort weighs 1.062 times as much as a gallon of water). These are of course completely different things. When I say they are the "exact same" I mean they are related is such a way that the measurements are proportional and measuring one directly measures the other (by multiplying or dividing by 131).
The third measurement is the Balling or Brix, BTW, and it measures the percentage of sugar by weight and what I find interesting is that it *doesn't* seem to be proportional. 20 on the Brix is *over* 1.080 on the gravity, while 10 on the Brix is *under* 1.040 on the gravity.
woozy
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Absolutely! Use a brewing calculator or software.
If it's extract its easy:
DME has 45 PPG (i'll explain that in a second)
LME has 37 PPG.
Multiply the pounds by the PPG (points per pound per gallon; it's a measure of the amount of sugar per pound that will effect the gravity), divide by the number of gallons. This is your gravity "points"
Suppose your 5 gallon batch used 6 lbs of LME and 2 lbs of DME.
(6*37 + 2*45)/5 = 62.4. So your O.G. was 1.062.
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If it's all-grain.... You can't really do it. The various grains will each have their own measure of *potential* PPG (amounts of sugar that will effect gravity) but you will only get 60-80 per cent of those sugars out. This is called you "efficiency" if you have a rough idea of your efficiency you can estimate the o.g. But the only way to actually know your efficiency is to actually measure your o.g. and compare to the the potential maximum PPG of the grains.
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mmm, yeah. But if your measure was 2% then 2% corresponds to 1.015. (Either look directly on your hydrometer and see that they both are on the same space, or divide by 131 to get .015267....) So your f.g. was probably 1.015... give or take a few points.
So.... your ABV was (1.062 - 1.15)*131 = .047*131 = 6.157 = 6.2%.
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Nobody does this but it's the same thing:
Your o.g. was 1.062. Take the .062 and multiply by 131 = 8.122. (Note: 1.062 and 8.2% are physically the same level on your hydrometer.) This means when you started you had the potential (if you were to convert *all* the sugar) to get 8.1% ABV. When you were done you had a potential alcohol reading of 2% meaning you had enough sugar *left* for a 2% ABV beverage. So the actual sugar converted made a 6.1% ABV!
Neat, huh?
