
10182013, 08:29 PM

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Working out ABV with multiple sugar additions


I really suck at this maths stuff (I normally just get ballpark figures using online calculators), so can someone help here?
Making this year's batch of ginger wine (about 20L). I used about half actual white grape must this time, bought from the local vineyards for a bargain price, rather than using raisins or whatever  figured it CAN'T do any harm! The rest of the bill is sugar. But my calculations are off because of this little experiment  I have gone from 1082 OG all the way to dry, or as near 1000 as makes no odds, which I didn't think would happen. Fermentation is still going strong, so I am happy to keep adding sugar until the yeasties give up, not bothered about a high ABV, and if I go overboard a bit with the sugar it doesn't matter as I plan to "backsweeten" anyway.
But how do I work out my ABV from multiple additions of sugar like this?
E.g. I have gone from
1082 > 1000
I then add, say 1kg of sugar to take it back up to around 1012. Then, (for example), it ferments back down to 1002 (or maybe it ferments dry again and I add MORE sugar).
How do I work out ABV from that, and is it even possible without getting a bit more involved with the volume, specific gravity of water/sugar etc?
I wouldn't even care that much about ABV, but I part of the batch is for friends, and they will want to know what they are drinking
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10192013, 03:08 AM

#2

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Tell them its 14.5%. They will never know otherwise.
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10192013, 03:29 AM

#3

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The math is pretty straight forward.
Sugar adds 46 points per pound per gallon. If we convert to your vastly superior metric units, that's:
(3.78541 L/gal) => 46 * 3.78541 = 174.13 points per pound per liter, and then
(20L batch) => 174.13 / 20 = 8.71 points per pound per 20L, and then
(2.20462 lb/kilo) => 8.71 * 2.20462 = 19.19 points per kilo per 20L.
So, for every kilo of sugar you add, figure you can add ~19 points to your effective starting gravity. Then, figure out your final gravity, and calculate your ABV by whatever formula you usually use.
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10192013, 04:40 PM

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Quote:
Originally Posted by MalFet
The math is pretty straight forward.
Sugar adds 46 points per pound per gallon. If we convert to your vastly superior metric units, that's:
(3.78541 L/gal) => 46 * 3.78541 = 174.13 points per pound per liter, and then
(20L batch) => 174.13 / 20 = 8.71 points per pound per 20L, and then
(2.20462 lb/kilo) => 8.71 * 2.20462 = 19.19 points per kilo per 20L.
So, for every kilo of sugar you add, figure you can add ~19 points to your effective starting gravity. Then, figure out your final gravity, and calculate your ABV by whatever formula you usually use.

THANKS! OK, so there was a bit of math(s), especially due to my reckless use of metric units . But that makes sense  I guess my main problem is I don't have an exact volume measurement, but I'll guesstimate, like I said, a ballpark figure is fine. Your calculation tallies with the hydrometer  I added 1kg sugar, and although it is hard to get it all dissolved, the hydro is indeed showing about 1.0161.018, presumably another 0.002 can be added for undissolved sugar, and that's perfect  thanks!
(I still hate maths though... My mind just goes a blank when I see any kind of formulas!)
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