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Old 10-30-2009, 11:30 PM   #11
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Quote:
Originally Posted by david_42 View Post
If you have a precision scale, weight out 25 gm of brew. Place it in a water bath and heat to 180F. After 15 minutes, remove from heat and re-weight. That will give you water by weight. ABW is the difference.
Nice. 79C is the boiling point of ethanol. To convert ABW to ABV (more common),

ABV = ABW * 1.27
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Old 10-30-2009, 11:33 PM   #12
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Originally Posted by menschmaschine View Post
Well, off the top of my head, if you have an accurate scale, you could take a sample of the end product, weigh it, boil off the alcohol at 173F, weigh it again to find out the alcohol by weight. Then multiply that number by 1.25 to get the ABV.
Your head and my head sure work differently

 
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Old 10-31-2009, 01:15 AM   #13
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I took a shot at this and apparently my Holiday Brew is 20%. Who knew!

Actually, I am pretty sure it is 8% and somewhere my measurements got f'ed. Likely I evaporated some water with the alcohol. Geez, I wish this actually worked!
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Old 10-31-2009, 01:46 AM   #14
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If you put away the car keys...it really doesn't matter

 
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Old 10-31-2009, 02:56 AM   #15
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A better way to do this is to take a beer sample of a known volume. test gravity. Boil it a bit and don't worry if you boil off water as well. Then let cool and top off with water to the initial volume. Test gravity again. With these two readings (apparent FG and real FG) you can determine OG, alcohol and all the other parameters.

I'd have to dig up the formula.

You can also determine OG and alcohol from a hydrometer and a refractometer reading. That's what's done in in-line monitoring systems in breweries. But they use oscillating U-tubes and sound velocity AFAIK.

Kai

 
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Old 10-31-2009, 04:21 AM   #16
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If you put away the car keys...it really doesn't matter
Truth that, but I like to track the numbers, just because. There's a lot of art to this, but the science side is fun too.
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Old 10-31-2009, 05:54 AM   #17
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Originally Posted by noblesquirrel View Post
that will only measure sugar in solution, you can't use it after fermentation for a reliable number, though it will give you a great OG.
This device is supposed to be use post fermentation to give the % alcohol by volume. Though the amount of sugar in the liquid will affect the reading, so it is meant for dry wines but it will give you a close estimate.

http://www.monashscientific.com.au/Vinometer.htm
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Old 10-31-2009, 05:20 PM   #18
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Interesting approach, Kaiser. I suspect one would need a precision hydrometer to get useful data.

passedpawn - try doing it with a good thermometer in the beer and stop the process as soon as the temperature goes above 173F.
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Old 10-31-2009, 05:36 PM   #19
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Quote:
Originally Posted by david_42 View Post
Interesting approach, Kaiser. I suspect one would need a precision hydrometer to get useful data.

passedpawn - try doing it with a good thermometer in the beer and stop the process as soon as the temperature goes above 173F.
I do use a Fluke 54 II Thermometer, so I trust the numbers (to the nearest 0.1C). I think the oven would be a better place to do this than the microwave, though, which is where I heated the water.

On a side note, my Holday Brew tastes very poor when hot and alcohol-less.

I just bottled some apfelwien... I think I'll go again with that stuff.
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Old 10-31-2009, 06:17 PM   #20
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Quote:
Originally Posted by Kaiser View Post
A better way to do this is to take a beer sample of a known volume. test gravity. Boil it a bit and don't worry if you boil off water as well. Then let cool and top off with water to the initial volume. Test gravity again. With these two readings (apparent FG and real FG) you can determine OG, alcohol and all the other parameters.

I'd have to dig up the formula.

You can also determine OG and alcohol from a hydrometer and a refractometer reading. That's what's done in in-line monitoring systems in breweries. But they use oscillating U-tubes and sound velocity AFAIK.

Kai
You can do with with real FG and real OG

A = (OE-RE)/(2.0665-.010665*OE)

A := alcohol % weight
OE := original extract
RE := real extract

The problem is that boiling beer for a bit will evaporate all of the ethanol about as well as boiling a sugar and water solution for a bit will evaporate all of the water, which is to say poorly enough that you would be better off using apparent extract to estimate the alcohol content.

 
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