I remember as a kid 25 or 30 years ago, my brother Wayne or his father-in-law Bob had a device that was able to measure alcohol content after fermemtation. You put the liquid into it and blew air into it. I remember seeing them test it using rye or vodka or something.
Dan
I have just started brewing my own beer and wine. I have made so rather
>odd concoctions the process. Some of the wine tastes good, some bad, and
>some like there is no alcohol at all. I want to know how I can figure the
>alcohol content of a drink. Does anyone know a home method of measuring
>alcohol content?
>
>
I don't know about testing something =that= high in alcohol, but a Vinometer is a glass funnel with a long tube on the bottom; you pour in DRY wine and wait for it to drip out of the bottom, then invert it and wait to see how far back down the tube the wine goes. You read it just like a thermometer.
They're not really different - 105 x 1.25 = 131.25, you're multiplying by that. The other is gravity divided by 7.49 and gravity is 1000 x specific gravity, so in specific gravity, you first multiply by 1000 and then divide by 7.49: 1000/7.49 = 133.5. So the first formula multiplies sg by 131.25, second by 133.5.
These all seem to be variations on the formula/approach from Duncan and Ainslie's Progressive Winemaking.
The only thing I find are "pre-pitch" (original gravity) tables. These cannot be used in the manner stated above because it fails to consider the effect that alcohol has on the "post ferment" reading. So far, I have not seen a single answer in this thread that considers this, so the answers thus obtained are wrong.
I am hoping that Jack or someone else here has a "post ferment/end alcohol" table that they could share with us. Tables, after all, are nothing more than a simple listing of all of the answers that a formula can provide. They have the advantage that folks that can't even _spell_the word algebra can look up the answers they need without having to understand the math. So - if someone has a suitable formula, it should be no problem converting it to a table.
Of course. No such table exists. And those who attempted to make one soon discovered that their formula/method doesn't work. Let me try (yet again) to explain this.
Example: Start a wine at 1.090. It finishes dry at 0.990. This is 100 points of SG drop. 90 of those points are due to the consumption and conversion of sugar, and the other 10 points are attributable to the fact that alcohol is less dense than water and therefore has an effect on our
*post ferment* reading (that was not present when we took our original gravity reading). This 10 point drop contributed *nothing* toward the amount of alcohol in the wine !!
Anyone who owns a triple scale hydrometer can do the following to prove this to themselves:
Assemble the following materials:
Distilled water
Table sugar (pure cane)
Pure alcohol (Everclear will do)
Mix up the following solutions, measure and record the SG for each:
Plain water.
A 12% solution of alcohol and water.
A 22% solution of sugar and water.
A solution which contains BOTH 22% sugar AND 12% alcohol with the remainder being water.
The first solution (plain water) is the reference point when we take our original gravity readings.
The second solution is the reference point when we take our post ferment (end gravity) readings.
The third solution is what we get when NO alcohol is influencing our SG readings.
The fourth solution is what we_would_get if alcohol was influencing our original gravity readings.
It will be seen that even though the 3rd and 4th solutions contain the same amount of sugar, we get *very* different SG readings. The only way to determine how much sugar is in solution 4 is to subtract the influence that alcohol is having on that reading.
It should then be easy enough to understand that trying to compare one reading that contains *no* alcohol to a second reading that *does* contain alcohol is like comparing apples and oranges !! HTMS
It seems to me that there is always an anomoly between final SG and what you might predict anyway. This may due to SS and/or dissolved substances in wine, which may vary from wine to wine.
To illustrate my point: Assume you have a bone dry wine of 12% abv. The density of ethanol is
789 kg/m^3, that of water is 1000. Thus, the SG of this solution should be:
No, I don't agree. Just to be on the safe side, I actually made up a 12% alcohol solution using Everclear and water from the tap. I am sitting here now, watching my hydrometer float in that solution. It reads
0.990 !! Yup - I just checked it again and it is_still_reading 0.990.
Do the exercise that I outlined above. It will be_very_ revealing !!
That was essentially the po> No, I don't agree. Just to be on the safe side, I actually made up a 12%
I just did it (not Everclear, but similar product) and got pretty close to 0.990. Perhaps the Everclear (or equivalent product) has dissolved substances that contribute just like those in wine might? Otherwise it simply doesn't make sense.
I just looked up Table B-3, page 394 of "Commercial Winemaking" by Richard Vine. For a solution of 12 % by volume, the table gives a specific gravity of
0.98238. For a solution of 12.09 % by weight, the table gives a specific gravity of
0.97897. Now I'm even more confused.
Lum, I am reluctant to chime in when you guys get going on the Chemistry, but aren't most spirits such as Everclear distilled? Wouldn't that esentially mean that it is alcohol only going into the bottle due to the process thereby eliminating any solids? Just pondering I guess.... John Dixon
John, My only experience with Everclear was many, many years ago when I was in college. I really don't know what Everclear puts in the bottles, but as I remember, a good time was had by all.
Ben wrote "Assume you have a bone dry wine of 12% abv. The density of ethanol is
789 kg/m^3, that of water is 1000. Thus, the SG of this solution should be: SG = (0.12*789 + 0.88*1000)/1000 = 0.975.
This would be true if the water and alcohol mixed without (for lack of a better term this early in the morning) dissolving into each other. The two liquids would have to remain separate at the molecular level even tho. mixed together.
However, water and alcohol do form a solution where molecules of each liquid intermingle and thus the specific gravity is different from the 0.975 value. The rest of the differences seen are due to different hydrometers, different temperatures at which measurements are made and other constituents in wine.
Lum's Commercial Winemaker reference gives the SG for 12% v/v alcohol as
0.98238. My Handbook of Chemistry and Physics gives the SG for this solution as 0.98435 [at 15.56C]. This reference also says the SG at 4C is
0.98344. I'm sure both of these references took great care in their measurements, yet there are differences.
Going back to the original question about how to calculate alcohol in dry wine. I totally agree with Frederick (Nov.30 post) that you can only consider the starting SG and a finished SG of 1.000 when you calculate alcohol. Beyond this simple calculation you will need a Ebulliometer ($663 at piwine) for more accurate alcohol determinations.
BTW Lum, my college fraternity held Purple Passion parties and sold tickets. Ten gallon crocks, grain alcohol (perhaps Everclear) and Welch's grape juice with a large block of ice. Those were interesting evenings because the mixture tasted just like grape juice. Creeped up on the guests real fast.
I certainly agree with you that alcohol will affect the final sg reading, but I disagree with your conclusions in this thread. As you say, a table just reflects an underlying formula. There are formulas out there that use final sg reading to calculate the PA, so tables based on these formulas then reflect both the starting and final sg.
To take one example, Duncan and Acton's Progressive Winemaking mentions a simple formula PA = (Gs - Gf)/7.4, where G is the gravity, defined as SG*1000. The constant 7.4 is actually an approximation - they also give a more complicated formula, where the constant depends on the starting gravity, but for simplicity, we can stick with the one value 7.4 here.
The point is that this does not falsely increase the amount of sugar in the must. Instead, the formula describes PA in terms of the total drop in gravity during fermentation (which directly depends on the sugar content of the must). As such, it's not better or worse by itself than formulas that describe the PA only in terms of the initial sg (sugar content). Which formula is better is an empirical question - any formula gives only a rough estimate of the final alcohol, so the quality of any formula would have to be measured against decent amount of real data.
To continue with the above formula - since it's linear in terms of the total gravity drop, we can use the method that Jack described and shift the final gravity to 1000 (sg to 1.000) if we shift the initial gravity by the same amount. And then a table that is based on this formula will show the PA reading for the adjusted Gs - the adjustment is needed because it allows us to start tabulating from sg 1.000.
One advantage of this approach is that it works equally well for all wines - dry or sweet. Only the Gf reading is needed for all cases. Formulas that work only with initial sg assume fermentation to dryness. If there is significant residual sugar left, the PA has to be adjusted, in which case one has to find out the RS amount and manipulate the table accordingly. So in this case, the final sg value becomes significant again.
The simple formula above also automatically corrects for presence of solids because of the subtraction. In terms of precision, the book claims the estimated PA is within +-0.5% of the actual value measured by an ebullioscope, for the alcohol range 10-14%. That's about as good as one could expect from any PA formula. The sample size is not mentioned.
I personally don't use this formula, but I can see the value of this approach. Mainly, I am hoping to make it clear here that approaches like this don't really compare apples with oranges, as there is nothing methodologically wrong in calculating PA in terms of total gravity drop vs in terms of initial gravity only. What matters is which formula makes a better prediction. In the absence of a decent comparative study, the choice is up to individual winemakers' preferences.
Sorry about the milligrams per liter typo. Factors of 1000 are usually significant, so thanks for pointing out my error.
Here is what I meant to say.
About 1.7 Brix of sugar has the potential for producing 1% (v/v) of alcohol (see "Concepts in Wine Chemistry," page 57).
1 gram of sugar in 99 grams of water = 1 percent by weight = 1 Brix.
10 grams of dissolved solids in 990 grams of water = 1 percent by weight = 1 Brix. Six to eight grams of dissolved solids (acids) per liter is equivalent to
0.6 to
0.8 Brix.. If 1.7 Brix = about 1% alcohol, then 0.8 percent of dissolved solids would be roughly equivalent to 0.47% alcohol (0.8/1.7 x 1% alcohol).
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