What is a Hydrometer?

The hydrometer is the most important tool in wine making. It is a long, thin tube with a weight in the tip. When put in a liquid, it will float and is used to measure the density of a liquid. For example, the specific gravity of water is 1.000.

There are several types of hydrometers but the Triple Scale is the one most used for making wine and measures:

  • Specific Gravity..........990 to 1.170
  • Balling.......................0% to 39% Sugar by Weight
  • Potential Alcohol.............0% to 22% by Volume

hydrometer The Specific Gravity scale measures how much sugar in a liquid (in our case, our "must"). As the sugar is dissolved, the specific gravity (SG) will increase because the sugar is increasing the density of the water. The ideal SG of a wine is 1.080-1.095 to produce an alcohol content of 11-12% in a finished wine.

The Balling (or Brix) scale shows how much sugar is present by weight.

The Potential Alcohol scale measures the percentage of alcohol that will be produced when all sugars are converted. In order to calculate the alcohol content, you must take a reading before fermentation occurs and when fermentation is completed. This gives you the numbers to calculate the finished wine's alcohol content.

The last reading is subtracted from the first reading to give you the amount of alcohol in your wine. If your starting reading is 13% and the last reading is 1%, you have a wine with an alcohol content of 12%.

Proper Use

Once you have put together all the ingredients of your "must" and the sugar has been added and stirred, take a hydrometer reading.
Just drop in your must and spin it. Give it a second for the bubbles to dissipate. Make sure it is not hitting anything. Once it stops spinning, it will level off and float. Take a reading at eye level to be accurate.

The specific gravity will tell you what the potential alcohol of your wine will be. Most recipes will give you a preferred starting S.G. If there is not enough sugar in the must to create the amount of desired alcohol content, add more sugar, a little at a time until you have the SG you want.

Do not add too much sugar. The amount of alcohol the yeast can produce is limited. Too much sugar will cause fermentation to stop.


Store your hydrometer in the case it comes in. They are delicate and should be handled with care. Do not shake them like a thermometer. Wash in room temperature water and always sanitize when working with your wine.
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