ABV Calculation Question

[Mim]

I had an original starting gravity of 1.074 and then added another 5 lbs of honey after a few days. The final s.g. after fermentation is over is 1.123. So how do I figure out what my final alcohol content is?

 

[WRATHWILDE]

Was this a 5 gallon batch, and if so how much honey did you add originally?

If it was a 5 gallon batch you can estimate 1% alcohol per pound of honey... minus the alcohol potential measurement on your hydrometer. Also you might have misread your Hydrometer, or you never had any fermentation take place. To start with 1.074 you probably added about 10 to 12 pounds of honey, I'm thinking 12 if the additional 5 pushed it to 1.123. In which case all your honey is accounted for and no fermentation ever took place.

Some things that might help us figure out where you stand...

What was the Original Recipe?

What type of yeast did you use?

How did you rehydrate the yeast?

What was the Temperature of the must when you pitched the yeast?

Exactly what steps did you take while making the batch?

Did you aerate/oxygenate the must during the first 3 days?

Did you use any nutrients?

What was your airlock activity like?

What is the temperature of the room you ferment in?

Let us know and we'll help the best we can... right now it looks like your yeast were not viable and fermentation never began.

Wrathwilde

 

[Mim]

I don't have the recipie right in front of me, so I'll have to fill in more acurate details later. It was originally a 5 gallon batch with 12 lbs honey. The other ingredients were yeast, water, and yeast nutrient. The room the fermentation was in is about 80F, and there was definetly fermentation as there was alot of airlock activity for about 2 weeks,and then it progressed slowly for about another week. I added the additional 5 lbs after about the first week. The yeast was White labs liquid yeast for sweet wine/mead and I had made a 2qt. starter to pitch the 5 gallons with.

This may turn out to be a moot point, however, because after letting a sample settle its really super sweet and I'm considering repitching the whole thing with a different yeast. The only concern then remaining would be the alcohol tolerance of the next yeast to use.

Thanks for the help.

 

[WRATHWILDE]

For the batch you have if your looking to end with a sweet mead you'll be wanting a yeast with about a 15% Alcohol Tolerance, For a semisweet 16%, for a dry mead anything 18% will do. You might try adding Lalvin K1V-1116, DV10 or EC-1118 and two or three more pounds of honey... All three are good strains for restarting stuck fermentations but they all have a tolerance of 18 to 20% if given ideal conditions. I listed them by preference (IMHO). You will only find DV10 in small quantities at morebeer.com however... they have the equipment to repackage Lalvin's commercial wine yeasts in homebrew friendly sizes.

DV10 can be found here...
http://morewinemaking.com/product.html?product_id=6281

A full range of yeasts here...
http://morewinemaking.com/browse.ht...7eaf792e2eb7e65ae61bbfdfd8ffc2&page=1#results

Hope this helps.

Wrathwilde

 

[Mim]

Thanks!

 

[Dan McFeeley]

I had an original starting gravity of 1.074 and then added another 5 lbs of honey after a few days. The final s.g. after fermentation is over is 1.123. So how do I figure out what my final alcohol content is?

Looks like this will take some complicated steps!

Are you sure the final gravity reading is right? That's awful high, even for a starting gravity prior to fermentation. For a five gallon batch starting at 1.074 with 12 lb.s of honey, adding a 2 quart starter and a few days later, five more lb.s of honey, given a final gravity reading of 1.123 after fermentations sounds like it stalled out and didn't finish.

Here's a few hints at calculating alcohol content. First, take a look at this article here:

http://science.howstuffworks.com/question532.htm

and you'll get an idea of the basic math involved in calculating alcohol content.

Here's a couple of formulas that are simple and easy to use.

Take your starting specific gravity, subtract your finished specific gravity and divide by 7.36. For example, 1080 - 995 = 85/7.36 = 11.55 % alcohol by volume. In winemaking circles, this is known at the Tritton formula.

This is one generally used by homebrewers.

Original Gravity minus Ending Gravity times 105 times 1.26 equals % Alcohol By Volume

Either one will get you there, although both are rough approximations.