Alcohol Content

ciderchic

Member
My hubby and I want to brew our own wine. We're looking into kits and such and plan to get started soon. Now, once we've made the wine, how will we know how strong it is? How will we know the alcohol content by volume?
 

wild

Moderator
Calculating the alcohol content of wine is done the same way as with beer or mead. You will need a hydrometer. If you didn't get one with the kit, your LHBS will have them available. They're inexpensive but fragile.

1. Drop the hydrometer into your wine before fermentation. Once the hydrometer has settled and is floating, record where the surface of the liquid crosses the gravity scale.
2. Place the hydrometer in your wine at the end of fermentation and record the specific gravity. The reading will be different, because as yeast metabolizes sugar, it produces ethanol and carbon dioxide. The carbon dioxide is released and the liquid that is left behind become less heavy.
3. Calculate the amount of alcohol in the wine by using this formula.

Percentage of alcohol = ((1.05 x (OG - TG)) / TG) / 0.79

OG is the original gravity reading that you took. TG stands for terminal gravity or the reading you took at the end of fermentation.

For example, if the original gravity was 1.06 and the terminal gravity 1.01, the equation would read:

Percent alcohol = ((1.05 x (1.06 - 1.01))/1.01) / 0.79

Therefore, the wine's alcohol percentage is 6.6.

There's also a calculator found on this page.
 

ciderchic

Member
Wow! I had no idea there was so much science/math involved in figuring alcohol content. Thanks for sharing the formula. Now that I know what we need to figure the alcohol percentage, I can make sure to buy a kit with a hydrometer in it.
 

wild

Moderator
Glad to help. Here's a link to Northern Brewery's page showing hydrometers so you'll know what you're looking at.
 

clarkdart

Active Member
I have caught the tools needed for this before but I have heard of people who can taste test or eyeball it, come to think of it that show Moonshiners does it quite a good bit. Is that really possible though? I would guess you need a few years under your belt before it is possible to be that accurate.
 

ciderchic

Member
If it were strong enough, you might could ballpark it through taste, but I doubt it would be highly accurate. I just want to be able to figure alcohol content so I can brag to all my friends about the strong wine I made. ;)
 
This is some really interesting information! I don't exactly know too much about alcohol content except for when I need a specific percentage for an herbal remedy I am making, but is there a way to figure out how alcoholic wine is without having to take the initial measurement? My grandmother made some wine for my brother and I, and I am a bit curious as to how alcoholic it really is.
 

wild

Moderator
Well there is one way...

Alcohol Content by the Boiling (Spirit-Indication) Method
This method was first proposed by M. E. Tabarié in 1830 as a simplified alternative to the distillation procedure. It is based on the principle that alcohol causes the same depression in specific gravity in wine as it does in pure water.
The method involves evaporating (boiling off) a portion of the wine sample until all of the alcohol is evaporated, and then replacing the evaporated volume with distilled water. The difference between the specific gravities of the wine and the volume-corrected residue are then used to estimate the specific gravity of the distillate, which represents the specific gravity of a pure water/ethanol mixture, from which the alcohol content can be estimated. The experimental procedure is summarized below.
  1. Measure the specific gravity (sgw) of the wine to be tested.
  2. Take a sample of about 250-500 mL (1-2 cups) of the wine and boil the sample down to approximately half of its original volume to drive off all of the alcohol.
  3. Allow the boiled residue to cool to room temperature.
  4. Add distilled water to the residue until the total volume is restored to the original sample volume.
  5. Measure the specific gravity of this volume-corrected residue sgr, which will be greater than sgw because the alcohol has been replaced by water.
It is recommended that a narrow-range hydrometer be used for the specific gravity measurements since small errors in these measurements can result in large errors in the results.
In addition to estimating the alcohol content, we can also calculate the solids content (true Brix) of the wine from the specific gravity of the volume-corrected residue. First we just need to convert the residue specific gravity measurement to a Brix value by using the Brix conversion equation. This conversion yields the solids content in % by weight of the residue. We then need to convert this value to the solids content in % by weight of the wine by multiplying by the ratio of specific gravities, or:

Bt= Btr·sgr/sgw

where
Bt = true Brix (solids content) of wine, % by weight
Btr = true Brix (solids content) of the volume-corrected residue, % by weight
sgw = specific gravity of wine
sgr = specific gravity of the volume-corrected residue
 
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