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Old 01-19-2013, 12:23 PM   #11
Hedley
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Nov 2011
Bristol, n/a
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Thanks. Ah I think I see.

So if I start with a reading of say 1.090, giving me a potential 12 per cent alcohol volume in the gallon, as long as I maintain that volume, by topping up with water to account for loses during racking, it shoud end up at 12 per cent still?

As I have NOT been topping up during my wine making so far, does that mean that my finished wines, being less than a gallon by a bottle or two, have actually been higher in alcohol than my starting potential?

 
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Old 01-19-2013, 01:12 PM   #12
TedLarsen
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May 2012
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Still, though, please don't miss the larger point: regardless of ABV, why would you water down your wine? Topping off with water is going to give you watered down wine, literally.

Most -- if not virtually all -- winemakers here top off their wines, and I daresay virtually of all of them top off with wine. Either top off with a commercial wine that is very similar to the wine you've made, or size the batch so that you have an extra half gallon or so that you ferment in a second carboy/bottle, and use that extra for topping off.

 
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Old 01-19-2013, 01:35 PM   #13
Hedley
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Nov 2011
Bristol, n/a
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What about if I took an SG reading at racking, and then made up a water/sugar mix to match that SG, which I used to top up? Would that keep everything constant, the sugar converting into alcohol?

 
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Old 01-19-2013, 01:41 PM   #14
novalou
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Jun 2012
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Quote:
Originally Posted by TedLarsen
Still, though, please don't miss the larger point: regardless of ABV, why would you water down your wine? Topping off with water is going to give you watered down wine, literally.

Most -- if not virtually all -- winemakers here top off their wines, and I daresay virtually of all of them top off with wine. Either top off with a commercial wine that is very similar to the wine you've made, or size the batch so that you have an extra half gallon or so that you ferment in a second carboy/bottle, and use that extra for topping off.
Yes, I agree. Top off with wine, juice with same SG, or rack into a smaller container.

If you do top up with water, it will lower you ABV.

 
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Old 12-06-2016, 07:01 PM   #15
PersephonesHell
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Dec 2016
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Quote:
Originally Posted by Hedley View Post
Hi all,

I have just started using the hydrometer and think I understand it.

However, in another thread someone mentioned that I should always top up my demijohn after racking so that it is nearly full (to stop oxidisation). That is all well and good, but I am now confused how this will affect the hydrometer reading.

I usually end up with about four and a half bottle's worth of wine at the end of the process. So I lose a bottle and a half through racking.

Is there a bit of maths I could do to adjust the SG reading depending on how much I have to top up with water? For example, say after the first racking I have lost half a bottle's worth. I add same amount of water to top up. Now I take an SG reading. Can I apply some formula to that to get an accurate reading based on the volume of wine I have effectively replaced with water?

Any help most appreciated.

Ross
So, I had to delve into my chemistry roots to get this formula, but so long as you use the same unit of measure throughout the whole thing, it works like a charm!

To start off, you need to measure 4 things:
1. The Specific Gravity of what you already have in your fermentor, we'll call it G1
2. The Volume of what you already have in your fermentor, V1
3. The Specific Gravity of what you are topping off with, G2
4. The Volume of what you are topping off with, V2

What ever you measure your volume with (gallons, liters, quarts, etc.) needs to be the same for both your V1 and V2 for this to work. You can't say your V1 is 3 gallons and your V2 is 1 quart. You would instead use 3 gallons and 0.25 gallons. Same goes for metric volume.

So here is the magic formula, keeping in mind that * is multiply and / is divide and anything in () you do first before going on to the next portion!

Final Gravity= ((G1*V1)+(G2*V2))/(V1+V2)

Might be confusing but let's try an example before you give up!

Say you have a must that, after you rack, is only 4 gallons. It's in a 5 gallon carboy, so naturally you need to top up with 1 more gallon. The S.G of your 4 gallon must is 1.07, and you're topping up with 1 gallon of 1.02 must from a previous batch.

Your measurements would then be:
G1= 1.07 and V1= 4
G2= 1.02 and V2= 1

Now plug it all in!

FG= ((1.07*4)+(1.02*1))/(4+1)

Then we start simplifying: Multiply 1.07 and 4, then 1.02 and 1

FG= (4.28+1.02)/(4+1)

Do it again: 4.28 plus 1.02, then 4 plus 1

FG= 5.30/5

Finish it off by dividing 5.30 by 5 and....

Your Final Gravity= 1.06!

I love this formula because even if you don't use water to top up, it still works! I like making cysers (love child of mead and cider) so I always top up with more apple juice, which does not have the same specific gravity as water (which is 1.000).

If anybody needs anymore clarification, or just wants help with their particular batch they are topping up, feel free to drop me a message!

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Old 12-06-2016, 07:20 PM   #16
bernardsmith
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Jul 2012
Saratoga Springs, NY
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One thing you might do that would remove all the issues of dilution or concentration (and so the need to use the Pearson's Square (see PersephonesHell post , above) would be to begin fermenting in a bucket and if you are planning on making 5 L of wine start with 6 or 7 liters all at the starting gravity you are aiming for (say 1.090). When you rack the first time you will rack into your 5 gallon carboy - and that will be full and the liter or liter and a half you have left over after racking you should rack into wine bottles and store these in your fridge. The cold will prevent them from actively fermenting. The next time you rack and lose an inch or two of wine you top up from the bottles you have had stored in your fridge. As that topping up wine reaches the ambient temperature of your fermenting room it will then start to ferment so the length of the fermentation of your wine will increase BUT you are neither diluting your wine nor adding anything "artificial" or anything you have not yourself made.

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Old 12-06-2016, 09:26 PM   #17
DoctorCAD
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Don't confuse SG with the ability to make alcohol. Every liquid has a Specific Gravity, and it is compared to pure water (which is 1.000). We assume that anything over 1.000 is sugar, just to make it easier to figure.

So, lets say that you have very hard water and its SG is 1.04, now what do you do?

I say don't worry about it. Keep the starting SG around 1.092 to 1.100 and let it ferment and you will end up with wine. Who cares if it is 14.1% or 13.5%, as long as it is over 11% it will be just fine.
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