how to calculate alcohol percentage?

[Steed]

ok so i made "mead of meath"
original gravity 1.100
current gravity 1.000 after 14 days

i took the ingredients out of the mead by straining through a cheese cloth.
i have the mead in a carboy but the mead level is below the the wide part of the carboy
i have a lot of head space

i plan on making sweet mead out of honey and adding it to the carboy to fill back up to the neck
the current ABV is 13.1% according to my hydrometer and chart.

if i add more mead to this batch how will i recalculate abv
/also should i add a pinch of yeast when adding the honey water to the batch of "mead of meath"

basically how do i calculate alcohol percentage in this circumstance and should i add more yeast when adding more honey water?

 

[SerifSansSerif]

not 100% sure here, but I'd take another measurement right before you add to your mead, then right after. This will allow you to calculate the new potential amount. (it doesn't help to just assume whatever the SG of your new additions are will result in that much more ABV. You're also adding liquid and in doing such, are creating a new solution. The difference between the start and end will give you a new number to work with. You want to take a new starting measurement because typically potential alcohol is calculated with water having an SG of 1. If your brew has since fermented and dropped below 1, then you will have to account for the additional sugar that raises the gravity to 1, and then all the sugars that bring it up over that... Make sense?)

Then you have to calculate the old ABV to get the new ABV based on the amount of liquid added.

This will be the same as calculating a percentage of a percentage....

Hmmmmm...

Lemme think this one out.

If you have 5 gallons of a 13% solution, and you mix it with, say, another 5 gallon solution at 0%, you should get, theoretically, a 6.5% solution.


If you had mixed 5 gallons at 13% with 2 gallons of new fermentables, you'd have an unknown amount at 7 gallons. 5/7ths of that would be at 13%, and 2/7ths would be at 0% to make the whole 7 gallons.

So my guess is you'll have something like x= your % in solution a, and y = the % in solution b

a=number of gallons in the solution a, b=the number of gallons in solution b, z=total gallons

so... x*a/z +y*b/z=resulting % of solution (new starting ABV)

so then you take that new starting ABV, and then ferment the new stuff on top of your old, and based on the new OG and FG, calculate the new ABV gained...

Anyone care to check my math/method?

 

[Steed]

not 100% sure here, but I'd take another measurement right before you add to your mead, then right after. This will allow you to calculate the new potential amount. (it doesn't help to just assume whatever the SG of your new additions are will result in that much more ABV. You're also adding liquid and in doing such, are creating a new solution. The difference between the start and end will give you a new number to work with. You want to take a new starting measurement because typically potential alcohol is calculated with water having an SG of 1. If your brew has since fermented and dropped below 1, then you will have to account for the additional sugar that raises the gravity to 1, and then all the sugars that bring it up over that... Make sense?)

Then you have to calculate the old ABV to get the new ABV based on the amount of liquid added.

This will be the same as calculating a percentage of a percentage....

Hmmmmm...

Lemme think this one out.

If you have 5 gallons of a 13% solution, and you mix it with, say, another 5 gallon solution at 0%, you should get, theoretically, a 6.5% solution.


If you had mixed 5 gallons at 13% with 2 gallons of new fermentables, you'd have an unknown amount at 7 gallons. 5/7ths of that would be at 13%, and 2/7ths would be at 0% to make the whole 7 gallons.

So my guess is you'll have something like x= your % in solution a, and y = the % in solution b

a=number of gallons in the solution a, b=the number of gallons in solution b, z=total gallons

so... x*a/z +y*b/z=resulting % of solution (new starting ABV)

so then you take that new starting ABV, and then ferment the new stuff on top of your old, and based on the new OG and FG, calculate the new ABV gained...

Anyone care to check my math/method?

ok so i am adding approximatly 1/3 a gallon of must to the brew..
if i followed the math correctly i will have 8-9% abv starting after adding the must. then i need to take gravity again and wait for fermentation... and then i add the new final gravity to the new OG and i get a the final abv that has a higher alcohol by volume??

 

[Steed]

ok so

Original gravity of mead of meath was 1.100

Original gravity of my sweet mead is 1.064

gravity of my original brew is 1.000 (mead of meath) currently.

combining the two they create a gravity of 1.020 (combined) currently (this number is irrelevant because fermentation already started)

i added about a third of a gallon of sweet mead to my original brew.


HYPOTHETICAL!!-:
1.064 OG of the sweet mead fermented to 1.000 = 8% ABV

1/3 of a gallon of sweet mead 1.064 fermented to 1.000 FG = 8% ABV
2/3 of a gallon mead of meath 1.100 fermented to 1.000 was 13% ABV

13+13+8=34
34/3= 11.3% total ABV for the original brew if final gravity is 1.000


and lastly if i get a full ferment of the batch of mead of meath + Sweet mead down to .990 final gravity the math is as follows.

1.100 fermented to .990 is 14.14% ABV
1.064 fermented to .990 is 9.71% ABV

1/3 1/3 1/3 3/3
14.14 + 14.14 + 9.71 = 37.99

37.99/3= 12.66% ABV

11.3% to 12.66% ABV is what i can expect based on my math.

i am going to take gravity again tomorrow

 

[SerifSansSerif]

ok so

Original gravity of mead of meath was 1.100

Original gravity of my sweet mead is 1.064

gravity of my original brew is 1.000 (mead of meath) currently.

combining the two they create a gravity of 1.020 (combined) currently (this number is irrelevant because fermentation already started)

i added about a third of a gallon of sweet mead to my original brew.


HYPOTHETICAL!!-:
1.064 OG of the sweet mead fermented to 1.000 = 8% ABV

1/3 of a gallon of sweet mead 1.064 fermented to 1.000 FG = 8% ABV
2/3 of a gallon mead of meath 1.100 fermented to 1.000 was 13% ABV

13+13+8=34
34/3= 11.3% total ABV for the original brew if final gravity is 1.000


and lastly if i get a full ferment of the batch of mead of meath + Sweet mead down to .990 final gravity the math is as follows.

1.100 fermented to .990 is 14.14% ABV
1.064 fermented to .990 is 9.71% ABV

1/3 1/3 1/3 3/3
14.14 + 14.14 + 9.71 = 37.99

37.99/3= 12.66% ABV

11.3% to 12.66% ABV is what i can expect based on my math.

i am going to take gravity again tomorrow

The math looks sensible, unless you already have a gallon, and are adding a third more. Then you have 3 thirds of a gallon at 13%, and 1 third at the hypothetical 8%, and altogether, you have 4 thirds... (which means you should divide by 4, and also add another 13%)

 

[HB_in_Subic]

Here is a calculator on Jack Keller's wine page http://winemaking.jackkeller.net/blending.asp

 

[Steed]

Here is a calculator on Jack Keller's wine page http://winemaking.jackkeller.net/blending.asp

Link doesn't lead to calculator

 

[SerifSansSerif]

Link doesn't lead to calculator

it did for me...

you have to scroll down a bit. It's the second calculator where it says:

Solving Adjusted Alcohol of a Blend

When:

the base wine has lower alcohol than the desired blend,
the fortifier (wine or spirit) has higher alcohol than the desired blend,
the % alcohol by volume of the base wine and fortifier are known,
the quantity of base wine and fortifier are known, and
you want to know the percent of alcohol by volume of the final blend....
Stated another way, if you have two similar wines of different percentages of alcohol by volume (abv) -- say 2 gallons of cherry wine with 11.6% alcohol by volume (abv) and 3 gallons of cherry wine with 15.3% abv -- and you decide to blend them together, what would the alcoholic content of the blend be? The calculator below will give you the answer. Simply enter the lower % abv of the base wine, the higher % abv of the fortifier wine, and the numberical units (bottles, liters, gallons, etc.) of both the base wine and fortifier as indicated. The only rule is that the numerical units of quantity must be of the same volumetric measure (bottles, liters, gallons, etc.).

Alcohol Quantity Adjusted
Base Fortifier Base Fortifier Alcohol

 

[Steed]

it did for me...

you have to scroll down a bit. It's the second calculator where it says:

I'm getting redirected to the homepage of that site and cannot find the calculator. Il search the site more later. It's not working right now

 

[SerifSansSerif]

I'm getting redirected to the homepage of that site and cannot find the calculator. Il search the site more later. It's not working right now

odd... :S