hydrometer

[murray123]

newb question...my hydrometer has the % alchohol listed next tot he specific gravity reading.....1.0 SG matches up with 0% alchohol...i understand how that works but if you ferment to below 1.0 sg say .990 does that add additional alcohol content?

 

[jamesngalveston]

lets see if i can explain.
if you look at your hydrometer and it says 0 percent alcohol at 1.000, rhen that means....if you add sugar to get to the 1.000 and it ferments to .990 you will have 0 percent alcohol in the juice.

now if you say....start at 1.040 and it goes to .990 you will have 5 percent alcohol.
if you add sugar and it reads 1.080 and it
goes to .990 your will have 10 percent alcohol.
its to find the potential alcohol based on starting specific gravity
and the ending specific gravity. (.990) considered a dry finished wine.


I start my wine at the sg of 1.120 and I finish at .990 giving me about 15 percent alcohol , on average give are take.

a handy abv chart here:

http://www.davesdreaded.com/homebrew-calculator/

 

[BernardSmith]

Short answer, Murray, is yes.
But I am not sure how useful the % alcohol reading is on the hydrometer since your interest is in the actual rather than potential ABV and the actual ABV is not knowable unless you know the starting gravity and not simply what the specific gravity reading is right now. Here's why: if your must started off with a gravity of 1.090 and three days later the gravity had fallen to 1.030 the reading would suggest that the ABV is about 3.9 but in fact it would be closer to 7.9 (The ABV would be the difference between 1.090 and 1.030, ie 1.060, and 1.060 converts to an ABV of about 7.9 %. That said, I think the best way to calculate ABV is to take your starting gravity subtract the final gravity (whatever it is, even below 1.000) and multiply that number by 131.

 

[DoctorCAD]

James, you're a bit off.

If the hydrometer reads 1.000 and you ferment down to .990, in theory there would be 1.31% alcohol (1.000-.990 * 131 = 1.31) Theory, since at 1.000 there would not be any sugar to ferment.

If you start at 1.040 and ferment to .990 you should have 6.55% (1.040 - .990 * 131 = 6.55)

If you start at 1.080 and ferment to .990 you should have 11.79% (1.080 - .990 * 131 = 11.79)

If you start at 1.120 and ferment to .990 you should have 17.03% (1.120 - .990 * 131 = 17.03)

Thats why kits start out around 1.092. Gives around 13% which is enough to keep nasties out and still not too strong that you can't drink it for two years.

 

[GreginND]

The alcohol scale on the hydrometer is a potential alcohol that could be produced at that point when starting the wine. If you have water with no sugar the SG will be 1.000. No sugar, no fermentation possible. Thus, 0 potential alcohol. If there is no alcohol there is no way to go below 1.000.

If you start from a higher SG and start fermenting, you are producing alcohol the more alcohol you produce, the more the potential alcohol scale is not correct. For example, if you start at 1.090 and ferment down to 1.000 all the alcohol makes the wine less dense. Thus the SG measurement is no longer reflecting pure water and sugar and there is still sugar present. And the SG can keep,going down as it ferments. We know about this error in the measurement and know to look for the end of fermentation to be lower.

Does that make sense? Bottom line, your triple scale hydrometer is only exactly accurate before any fermentation begins. So you always have to calculate the change in SG from the beginning.

 

[BernardSmith]

If the hydrometer reads 1.000 and you ferment down to .990, in theory there would be 1.31% alcohol (1.000-.990 * 131 = 1.31) Theory, since at 1.000 there would not be any sugar to ferment.

.

Don't intend to hijack this thread about how to read a hydrometer but I really think theory and reality are identical but your "theory" is slightly off.

To nit pick: True, water with no sugar will have a reading of 1.000 at the temperature at which the hydrometer was calibrated but if your liquid contains a significant quantity of alcohol together with water it ought to read below zero even if there was still some fermentable sugar in the mixture because alcohol has less buoyancy than water so the hydrometer would float lower in the cylinder. If the liquid contained only alcohol and no water - which I think is not possible but that is another story - the hydrometer would be WAY below 1.000.

A reading of 1.000 really only tells you that the liquid has the same buoyancy as water. It does not in fact truly tell you how much sugar is in the liquid or what else may be in the liquid or what the liquid is. We use an hydrometer as a rough and ready tool to estimate the sugar content but in fact we are measuring buoyancy and treating the buoyancy as a reasonable indication of the sugar content. That may be "good enough for our purposes" but we are not really measuring sugar content.

To sum up - a reading of 1.000 does not really tell you that there is NO sugar in a liquid. That is why wines can continue to ferment in a bottle if that was the assumption someone makes and then proceeds to bottle. A reading of 1.000 simply tells you that the mixture you have is similar to the "gravity" of water: mix in a specific quantity of sugar and add a specific quantity of alcohol to that liquid and the hydrometer will still show 1.000.

 

[seth8530]

Don't intend to hijack this thread about how to read a hydrometer but I really think theory and reality are identical but your "theory" is slightly off.

To nit pick: True, water with no sugar will have a reading of 1.000 at the temperature at which the hydrometer was calibrated but if your liquid contains a significant quantity of alcohol together with water it ought to read below zero even if there was still some fermentable sugar in the mixture because alcohol has less buoyancy than water so the hydrometer would float lower in the cylinder. If the liquid contained only alcohol and no water - which I think is not possible but that is another story - the hydrometer would be WAY below 1.000.

A reading of 1.000 really only tells you that the liquid has the same buoyancy as water. It does not in fact truly tell you how much sugar is in the liquid or what else may be in the liquid or what the liquid is. We use an hydrometer as a rough and ready tool to estimate the sugar content but in fact we are measuring buoyancy and treating the buoyancy as a reasonable indication of the sugar content. That may be "good enough for our purposes" but we are not really measuring sugar content.

To sum up - a reading of 1.000 does not really tell you that there is NO sugar in a liquid. That is why wines can continue to ferment in a bottle if that was the assumption someone makes and then proceeds to bottle. A reading of 1.000 simply tells you that the mixture you have is similar to the "gravity" of water: mix in a specific quantity of sugar and add a specific quantity of alcohol to that liquid and the hydrometer will still show 1.000.

Just to add to this, I would like to state that their are many ABV equations out there. All of them attempt to create a more accurate ABV formula. However, they all have their weaknesses. So keep in mind that the hydrometer is a tool for estimating abv. However, the more important purpose, in my mind, is estimating initial sugar concentration and much more importantly to monitor the progress of your fermentation.

Ie, the change in gravity is an extremely important metric to watch if you want an idea of how healthy your fermentation is and what exactly is going on with the yeast.

 

[jamesngalveston]

doctorcad..i was using my hydrometer scale that is printed on the side of it.
for his reference, since that is what he was doing....

the actual sg is variable...with calibration, and the temp of the wine.
all plays in...its a close guess...
if you want to know the true alcohol...you will have to get a liquor hydrometer, its a little more accurate

 

[murray123]

So if my triple scale hydrometer reads 1.09 and the % potential reads (i think) about 12% potential alcohol does that mean it would be 12% if fermented to 1.0 SG or a .990 SG......not a big deal to me just want to know what is right

 

[Kraffty]

Based on 1.0 but if you end up at .990 you'll be at 13.1% approx.

 

[sour_grapes]

To SG = 1.000.

 

[michael-s]

The container my hydrometer came in has this information printed on an included paper which was printed front and back and that is the reason for both pics. Anyway, it explains quite clearly , where I marked with brackets, how to calculate your alcohol content.

 

[jamesngalveston]

ok, lets see if this makes sense to you.
.990 is at the very end of fermetation, not the start.
when reaches the sg of .990 It is finished....

look down to you see 1.140, that is the start of your wine with sugar added.
as it ferments, your hydrometer will show less and less of the physical hydrometer and will go up the scale.
so if you start at 1.140, and finish at .990 you have the potential of 18 percent.

if you start at 1.020 and finish at .990 it has a potential of 15 percent.

 

[michael-s]

Jamesngalveston using info that came with my hydrometer this is what I end up with......
Start fermentation SG 1.140 = 18.6 % alcohol
End of fermentation SG 0.990 = (-1.3 %) alcohol

Those 2 numbers give you a final alcohol content of 19.9 %

 

[jamesngalveston]

no
if you start at 1.140
and end at 0.090 then its an estimate of 18 percent.

you do not add them together.

.990 is a mean reference number...means your wine is dry, no more sugar.

 

[jamesngalveston]

it could be anywhere from 17.5 to 20. percent, depending on hydrometer calibration, what temp you fermented at, etc.

if you want to know the exact alcohol contend you will have to buy a Proof & Tralles hydrometer

 

[jamesngalveston]

copy and pasted wrong, sorry...Proof /Tralles doesnt work on wine.

 

[Julie]

Here is a good formula you can use to calculate what your ABV would be. Beginning hydrometer reading (sg) - ending hydrometer reading (fg) x 131. And understand your wine will not always end at .990. Wine is considered done fermenting at 1.000. It will normally go beyond that but I did not want you to think it has to go to .990 before it is considered finished. Once it gets below 1.000, check it for the next week or two and if you can get the same reading three times, then that reading is your final reading.

 

[michael-s]

Julie....... using the formula you suggest you end up with the same % alcohol that I said I got ( 19.65% so very close) following tables included with my hydrometer..... thank you.

those instructions I posted with my first message say in example 1, if your finished sg is greater than 1.0 then you subtract the numbers you get from the table from each other to get your finished alcohol %

the 2nd example they give is when your finished sg is less than 1.0 (example .990) then you add the 2 numbers together you get off of the table to get your final alcohol %.

Sorry about those 2 pics have low resolution making it difficult to read. If someone would like to see higher resolution of those instructions let me know and I will post them.

 

[Julie]

Julie....... using the formula you suggest you end up with the same % alcohol that I said I got ( 19.65% so very close) following tables included with my hydrometer..... thank you.

those instructions I posted with my first message say in example 1, if your finished sg is greater than 1.0 then you subtract the numbers you get from the table from each other to get your finished alcohol %

the 2nd example they give is when your finished sg is less than 1.0 (example .990) then you add the 2 numbers together you get off of the table to get your final alcohol %.

Sorry about those 2 pics have low resolution making it difficult to read. If someone would like to see higher resolution of those instructions let me know and I will post them.

If you are getting the same ABV with my calculations, then you are getting to the same place as I am but by a different route.