View Full Version : How do I calculate alcohol in mead?

DGettere

03-31-2009, 10:54 AM

Hi. I was wondering how I calculate the estimate of alcohol in mead?

Such as if I make a 5 gallon batch, using 15 pounds of honey and

say a yeast like D47 which is est at 14% alcohol.

Using these amounts I would figure the O.G. to be 1.107 and the volume to be 5.00 gallons. But now how do I figure out the estimated alcohol? How is the F.G. calculated?

Thanks

DG

wayneb

03-31-2009, 11:52 AM

Well, strictly speaking you don't calculate the final gravity, you measure it with a hydrometer. It isn't possible to forecast exactly where your mead will finish, since even though you know the nominal ethanol tolerance of the yeast that you use, variations in how you manage your fermentation will sometimes cause the yeast to finish significantly higher, or lower, than that nominal value.

So, measure your final gravity, and based on that along with either an estimate of your initial gravity (based on recipe quantities) or an actual measurement of your starting gravity, you can use the mead calculator (click on the link to the left of this page) to get your final ABV.

akueck

03-31-2009, 12:03 PM

Yup, Wayne is correct. You can "guesstimate" where your ABV will wind up using the OG and the tolerance of your yeast. If you assume you will be able to get exactly the amount of alcohol your yeast will make and no more, an OG of 1.110 will be 14% ABV. A lower OG will produce less alcohol, and a higher OG will produce the same amount (14%) and leave sugar behind. Like Wayne mentioned, a lot of variables will affect the real result, so you'll just have to try it out and see how it goes.

I would suggest making your first several meads with the same yeast strain. This way you can see how different batches, temperatures, etc etc, will affect how much alcohol your yeast produces using your methods. Then you'll have a better estimate going forward. For example, I use D47 a lot and I know I can get 14.5-15% in a traditional and 17% or so in a cyser.

DGettere

03-31-2009, 01:06 PM

Thanks all. Learning lots here!

What I'm trying to wrap my head around is how to figure out how to make a sweet vs dry vs somewhere in between mead. For example if I use 15# in 5 gallons I get X 12# in 5 gallons I get Y and 10 # in 5g I get Z or what would happen if I use 20# in 5g.

I read where a sweet mead is O.G. 1.120-1.130 T.G. 1.005-1.015

a medium mead is O.G. 1.105-1.120 T.G. 1.00-1.005

and a dry mead is O.G. 1.085-1.105 T.G. .990-1.00

So lets see if I can answer my question then: 15# in 5g will be about 1.107 and "should" finish on the border of a medium to sweet. 12# will be about 1.085 and "should" finish on the border of medium to dry. Looks like 10# would be 1.085 and would be too low??? And 20# would be about 1.142 and would most likely have problems due to being too high?

So can I assume that if I hit these O.G.s that I'll have a dry/medium/sweet ?

If that's true, how does yeast type come into play? Because I could make something with a 12% or an 18% yeast, I would just have to understand the yeast then?

ndbrewlady

03-31-2009, 01:26 PM

Your yeast comes into play. If you use a 14% yeast (71 B for example) you will have more sugar left over then a 18% ( 1118 ) yeast.

And of course any yeast can ferment more or less of the sugar, just depending on how the process goes, the amount of nutrients the temp and so on.

DGettere

03-31-2009, 01:43 PM

Your yeast comes into play. If you use a 14% yeast (71 B for example) you will have more sugar left over then a 18% ( 1118 ) yeast.

And of course any yeast can ferment more or less of the sugar, just depending on how the process goes, the amount of nutrients the temp and so on.

OK, so say I was going to make a medium mead which should be S.G. 1.105-1.120 T.G. 1.00-1.005. What happens if I use 71B vs 1118?

Without fully understanding I would say that 1118 will metabolize more sugar into alcohol and it will reduce the T.G. - but how will that change the T.G. vs using 71B? Because if the yeast is different, how will I be able to guess what my T.G. will actually be or won't I be able to estimate it?

Medsen Fey

03-31-2009, 03:31 PM

Welcome to GotMead DGettere!

If I'm understanding correctly, you are trying to understand how the yeasts alcohol tolerance plays into the gravity calculations.

Well, a simple calculation for ABV is Gravity fermented * 131 = ABV.

You can reverse this and say ABV/131 = gravity fermented.

So a yeast with an alcohol tolerance of 18% ABV (like EC-1118 ) could be expected to consume 137 gravity points (dropping the gravity by 0.137) assuming it reaches its tolerance and doesn't get stuck.

A yeast with 14% ABV (like 71B) could be expected to consume 107 gravity points.

Again these are estimates and the yeast sometimes go much farther than you expect (I have had that happen so often it's not funny), or sometimes they may stall out a bit short. This can depend on many factors including starting gravity, pH, temperature, rehydration process, and myriad other unidentified parameters.

So if you start with a recipe that has an initial gravity of 1.120 and you use EC-1118 which can chew up 0.137, you will wind up with a bone dry mead with a gravity below 1.000.

I hope that helps.

Medsen

DGettere

03-31-2009, 05:29 PM

So a yeast with an alcohol tolerance of 18% ABV (like EC-1118 ) could be expected to consume 137 gravity points (dropping the gravity by 0.137) assuming it reaches its tolerance and doesn't get stuck.

A yeast with 14% ABV (like 71B) could be expected to consume 107 gravity points.

So if you start with a recipe that has an initial gravity of 1.120 and you use EC-1118 which can chew up 0.137, you will wind up with a bone dry mead with a gravity below 1.000.

Medsen

Thanks for the welcome and the reply! I think I'm getting closer to the answer I'm searching for now. You said that a yeast with an 18% ABV could be expected to consume 137 gravity points and a 14% ABV yeast could be expected to consume 107 gravity points. Where did you get those numbers, and is that accurate if you different O.G.s?

Medsen Fey

03-31-2009, 05:49 PM

Well, a simple calculation for ABV is Gravity fermented * 131 = ABV.

You can reverse this and say ABV/131 = gravity fermented.

So a yeast with an alcohol tolerance of 18% ABV (like EC-1118 ) could be expected to consume 137 gravity points (dropping the gravity by 0.137) assuming it reaches its tolerance and doesn't get stuck.

I'm sorry, I should have been a little more clear.

If the ABV/131 = gravity fermented (the difference between Starting Grav and Final Grav)

then with a yeast with a tolerance of 18%, you divide 18/131=0.137

with a yeast that has 14%, you divide 14/131=0.107

So if you start the same mead with a gravity of 1.120, and use the yeast with 14% ABV tolerance, you will consume about 0.107 (107 gravity points) leaving an expected final gravity somewhere in the neighborhood of 1.013 which would be a little sweet.

That would be the difference in using the two yeasts starting at the gravity of 1.120. One will finish bone dry with around 16% ABV and the other will finish sweet with about 14% ABV.

I hope that is more clear.

Medsen

Oh, as for the original gravity having an effect - the answer is yes it can, but not usually in the normal range we make meads with. As you start with higher gravities, the osmotic stress tends to reduce the final alcohol tolerance of the yeast so they will produce less alcohol (and reduce the gravity by less) than if you started at a more reasonable level of sugar. This generally doesn't become a significant issue with the gravities below 1.140-1.150.

akueck

03-31-2009, 05:59 PM

The "gravity points" are directly related to the gravity readings. An OG of 1.137 is the same as saying that you start with 137 gravity points of sugar--just take whatever comes after the decimal point. More accurately, gravity points = (SG-1)*1000, so 1.050 is also "50 gravity points". You'll see beer recipes give readings in this style with OG/FG readings like 57/12.

What Medsen is saying is that each yeast will be able to consume different (maximum) amounts of sugar. Put into the same must with an OG of 1.140, EC-1118 "could" achieve a FG of 1.003 but 71B would only get down to 1.037. 1.000 (or zero gravity points) is roughly the lower bound, however, so if you started with an OG of 1.100, both yeasts "should" give you a FG of 1.000 or roughly 13% alcohol.

In practice you don't want to have an OG above about 1.125-30 because that's a lot of sugar and yeast health is compromised quickly at high gravity without lots of work on your part. This is another factor that will influence alcohol tolerance/attenuation achieved. So to answer your question about the accuracy of the "gravity points consumable" vs. OG--yes it does depend on OG if it's high enough.

Argh, Medsen you beat me to it. Well, ditto then. ;)

Medsen Fey

03-31-2009, 06:05 PM

Argh, Medsen you beat me to it. Well, ditto then. ;)

Yeah, but I think your explanation is more understandable, so like everything else in meadmaking, being in a hurry is no help.

DGettere

03-31-2009, 08:19 PM

By George, I think I've got it! I appreciate everyone's willingness to help! I hope to be able to pass off some of my knowledge some day!

So while the calculations are accurate, the yeast are the variable in the equation as they may or may not reach (or possibly even exceed) the listed alcohol percentage. So that being said, these are more theoretical than actual because of the variability of the yeast?

akueck

03-31-2009, 08:34 PM

Yup. The yeast are the big variable. Experience will help you figure out where things tend to land for you. That is to say, make lots of mead! ;D

GeorgiaMead

03-31-2009, 08:39 PM

i'm a cheater i use this.....

http://www.realbeer.com/hops/kcalc_js.html

;D

DGettere

04-02-2009, 10:31 PM

What happens if I don't get the O.G., is there a way to calculate the alcohol, or do I just have to guess?

Medsen Fey

04-02-2009, 10:42 PM

You can calculate the original gravity if you take a hydrometer reading and a refractometer reading. You plug them into a calculator like THIS (http://brew.stderr.net/refractometer.html). I'd say measure the OG at the beginning - it makes life easier.

DGettere

04-03-2009, 10:14 AM

What I did was made a 1 gallon batch of a cinnamon vanilla mead and when I racked that to a secondary I used that yeast to make another batch. I had an initial gravity of 1.084 and wanted to get a little more out of it so I added an unknown amount of honey that was left in the bottom of a container a day or two later. I'm thinking maybe 2 cups but dummy me didn't measure it first before I added it. Its not the end of the world, but since I'm starting to understand this, I was just wondering.

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