GETTING TO KNOW YOUR HYDROMETER

From time to time we receive calls regarding the use of the
hydrometer: about how a reading is actually taken; what the
readings actually mean and so on. Let's face it, unless you've
used a hydrometer before it is somewhat of a foreign concept.
I will attempt to clear up some of the confusion here.

What the hydrometer can do for you is two-fold. First, it allows
you to track the progress of your fermentation by taking
readings throughout the fermentation. Secondly, it can tell you
what the alcohol percentage of your finished product is by
taking a reading before fermentation and one after
fermentation and comparing the two.

How To Take A Hydrometer Reading

To take a reading with the hydrometer it is required that you
get the hydrometer to float in the juice to be tested. Whether it
is floating in the plastic tube it came in, in a test jar you
purchased, or floating in the entire batch makes no difference,
as long as it is floating you will be able to take a reading.

Once the hydrometer is floating, you take the actual reading
by seeing where the surface of the liquid crosses the scale on
the hydrometer.

Different Scales On The Hydrometer

Typically, there are two scales on the hydrometer that you are
concerned with: the "Specific Gravity" scale (normally labeled
as S.G. or SP GR) and the "Potential Alcohol" scale.

Specific Gravity is referred to by most books and recipes. It is
simply a scale based on the weight of water. The "Potential
Alcohol" scale is used to easily determine how much alcohol
was made or can be made.

Learning About The "Specific Gravity" Scale

Just for fun, if you float the hydrometer in water and read the
Specific Gravity scale, the surface of the liquid would cut across
the hydrometer at the 1.000 mark, towards the top of the scale.
Most hydrometers are calibrated to be most accurate at 60
degrees Fahrenheit. So, if the water is warmer or cooler, the
reading may be off just a hair.

When you take a reading in fruit juice or water that has had
sugars added to it, the hydrometer will float higher than before.
This is because the liquid is now heavier than water which in
turn increases the buoyancy of that liquid.

For example, it you completely dissolve 2 pounds of cane sugar
into 1 gallon of water, you will have a Specific Gravity reading of
1.068. You will find this on the Specific Gravity scale by going
down from the 1.000 to the 60. The 60 represents 1.060. In
between the 60 and 70 you will see several tick marks. Each
one represents two points. So, the fourth tick would be the 8.
This is the point on the hydrometer that represents 1.068.

Learning About The "Potential Alcohol" Scale

If you put your thumbnail at the 1.068 mark mentioned above
and roll the hydrometer around to the Potential Alcohol scale
you will see it matches a reading of 9%. What this means is that
if you were somehow able to get this liquid to ferment all of the
sugars it contained into alcohol, the result would be a liquid with
9% alcohol by volume.

As the wine ferments you will see the Potential Alcohol reading
becoming lower and lower. What this means is that as the
sugars in the juice are turned into alcohol the potential for more
alcohol is reduced.

To find out what the actual alcohol percentage of a finished
wine is, you would subtract the ending fermentation reading
from the beginning fermentation reading.
 

Typical Example Of Hydrometer Use

For example, lets say you have 5 gallons of freshly pressed
grape juice. You take a beginning reading of 12 percent on the
Potential Alcohol scale of your hydrometer. When the
fermentation is complete, you take another reading with the
hydrometer that indicates a Potential Alcohol of 1 percent. You
then take the 1 and subtract it from the 12, giving you a total of
11 percent alcohol. This means that the fermented juice now
has 11 percent alcohol by volume.

In Conclusion

If you are not currently using a hydrometer, I would suggest that
you might consider using one in the future. While it may be a
little intimidating at first, once you use one you'll soon discover
that there is not much to it. The benefit is the hydrometer allows
you to have much more control over your batches. With the
hydrometer you can control the alcohol content of your wines,
monitor the fermentation's progress, as well as determine when
the wine is actually done fermenting.

* To view the hydrometers we have right now on our
website go to:

Wine Making Hydrometers