HYDROMETER SCALES AND WHAT THEY MEAN

There always seems to be a little confusion going on about the
different scales you will find on various hydrometers for making
wine. So, I thought I would take a little time here to give some
background and explain what is really going on when we take a
hydrometer reading.


The Basic Idea Behind the Hydrometer

The whole premise behind the hydrometer is: "the heavier the
liquid being tested, the higher the hydrometer will float" - in
other words, the buoyancy of the liquid increases with the weight
of the liquid. For example, if you float a hydrometer in water,
it will float much lower than if you put the same hydrometer in
maple syrup. This is because the maple syrup weighs much more
than water.

Some people have a problem thinking in terms of a liquid having a
weight. For some it is easier to think in terms of thickness. The
same can be applied by saying, "the hydrometer floats higher in
maple syrup because it is 'thicker' than water". This is okay
too.


Why do we even care how high or low a hydrometer floats?

During a fermentation, basically thick sugars are being turned
into thin alcohol. In other words, the juice is going from heavy
to light. This also means that throughout a fermentation the
hydrometer will float at different heights, giving different
readings.

At the beginning of fermentation the hydrometer will float at its
highest. At the end of fermentation the hydrometer will float at
its lowest. And, throughout the fermentation it will float
everywhere in between those two readings. It is with these
various readings that we are able to monitor the progress of the
fermentation and track the alcohol that has been produced.


The Hydrometer Scales

* Specific Gravity.
This particular scale is the most commonly used among home wine
makers and is referred to in most home wine making books. It
should be thought of only as a way of keeping in step with any
recipes you may be using that make references to this particular
scale.

The Specific Gravity scale is based on the weight of water. If
you float a hydrometer in water it will read 1.000 on the
Specific Gravity scale. At the beginning of fermentation a
typical reading might be 1.090. This means, for example, that the
juice at that point weighs 9 percent more than water, or the
juice is 9 percent thicker than water.

When all the sugar is turned into alcohol you will have a reading
on the Specific Gravity scale that is less than water - typically
around .995. This means that the juice weighs less than water, or
it is thinner than water by a half of a percent.

Again, simply think of the Specific Gravity scale as just a very
common scale that allows you to follow the progress of your
wine's fermentation, and to stay on track with books and recipes
that mention it.


* Potential Alcohol.
This scale tells the winemaker how much alcohol can be made from
the sugars that are currently in the juice. A single reading on
the Potential Alcohol scale can NOT tell the winemaker how much
alcohol is already in the wine. It can only tell the winemaker
how much MORE alcohol can be made, based on the liquid's current
weight or thickness, or in other words, how much sugar still
remains in the juice.

The Potential Alcohol scale on most hydrometers usually ranges
from 0 to 20 percent alcohol. So, for example if you mixed a
recipe together and took a reading of 13 percent on the Potential
Alcohol scale before the fermentation began, this means that
there is enough sugars in that juice at that point in time to
potentially produce 13 percent worth of alcohol.

Now, not all fermentations use up every bit of sugar, so when the
fermentation has finished, you can take a second reading to see
how much "potential alcohol sugar" has been left over, if any. By
comparing these two readings, you can then determine the current
alcohol level of your wine.

Let's say for example, that a juice started out with a reading of
13 percent before the fermentation started, and had a reading of
1 percent after the fermentation stopped. By comparing the two
readings you can determine that the juice now contains 12 percent
alcohol. Another way to look at it is that the fermentation moved
12 points across the scale, resulting in 12% alcohol.


*Brix Scale (Also known as Balling).
This hydrometer scale is used mostly by grape growers and
commercial wineries. It is also referred to in more advanced home
wine making books.

The Brix scale is based on percentage of sugar that is in the
liquid by weight. Typically the scale will go from 0 to 30 on
most wine making hydrometers. If you have a grape juice that
reads 24 on the Brix scale, that means that the juice is made up
of 24% sugar by weight.

Vineyards use this scale to determine if the sugar level of the
grape is sufficient for harvest. Wineries use this scale to
determine if the juice has sufficient sugar to produce the
alcohol level they desire.

*Sugar Scale.
This scale tells the winemaker how much sugar is in the juice at
a given time. The readings are given in ounces per gallon. For
example, you might have a reading at the start of fermentation of
35. This means that you have 35 ounces of sugar per each gallon
of juice.

Now, this does not necessarily mean that you added 35 ounces of
sugar for each gallon of juice. Some of the sugar comes naturally
from the fruit as well. For example in the case of grape juice,
you can have a reading of 35 without adding any sugar at all; the
sugar comes completely from the grape itself.

Why is this important? This information in itself is not really
important. But, when used in conjunction with other scales on the
hydrometer it can be very, very valuable.

Let's say that you have a recipe that says to add sugar to the
juice until the Specific Gravity reading is 1.072. So, you mix
all the ingredients together as the recipe calls for, except for
the sugar. You take a reading and find that your Specific Gravity
reading is 1.046, but you need to be at 1.072.

This is where the sugar scale comes into play. By determining how
many ounces of sugar is represented in each gallon of juice now,
at a reading of 1.046, and determining how many ounces of sugar
will be represented in the juice at a reading of 1.072, you can
then determine how much sugar you need to add to a juice to take
your from a reading of 1.046 to 1.072.

When looking at a hydrometer that has both the Specific Gravity
scale and the Sugar Scale, you will see that a Specific Gravity
reading of 1.046 also equals 20 ounces of sugar per gallon.
Likewise, a reading of 1.072 equals 30 ounces of sugar per
gallon. Armed with this information you can see by comparing
these two readings that to raise the hydrometer reading from
1.046 to 1.072, you need to add 10 ounces of sugar for each
gallon in the batch - this is the difference between 20 and 30.

The Sugar Scale can also be used in conjunction with the
Potential Alcohol scale. For example, if you have a Potential
Alcohol reading of 8 percent and you want it to be 12 percent,
just look up the corresponding ounces on the Sugar Scale to
determine the amount of sugar to add.

In this example, a potential alcohol of 8 equals 26 ounces of
sugar per gallon, and a potential alcohol of 12 is equal to 38
ounces of sugar per gallon. The difference is 12 ounces of sugar
per gallon. This is the amount of sugar to add for each gallon to
increase your potential alcohol from 8 to 12.

For more information about the hydrometers we offer, go to:

Wine Making Hydrometer

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E. C. Kraus

Home Wine & Beer Making Supplies

Address: 733 S. Northern Blvd. - P. O. Box 7850 - Independence, MO  64053

Phone:(816) 254-7448  Fax:(816) 254-7051  Toll Free: (800) 353-1906

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