Using a Hydrometer in Winemaking

Using a Hydrometer in Winemaking

Using a Hydrometer in Winemaking

A hydrometer is an instrument used to measure liquid density. It is a sealed glass tube with a weighted bulb at one end, winemakers use this instrument to measure density of juice, fermenting wine and completed wine in relation to pure water. This ratio is called specific gravity (SG).

Five good reasons to use a Hydrometer:
1) Measure the sugar content of your must.
2) Calculate the potential alcohol content of the must, before it begins to ferment.
3) To see how fermentation is progressing.
4) Find out how much alcohol is in the finished wine.
5) Determine if fermentation is complete.

Start by measuring and recording Specific Gravity

Wine Thief and Hydrometer

Take a sample of your must or wine with a sterilized wine thief and transfer some to your hydrometer testing flask. Read the hydrometer and write the reading, date and temperature. Note that when you take the reading, you read the lowest portion on the meniscus.

This figure will tell you how much sugar is in your must and the potential alcohol content.

TIPS: Use a spray bottle with a sulfite solution to sanitize any test equipment.

Always spin the hydrometer to dislodge bubbles that may be attached to the hydrometer ,this could give you an inaccurate reading.

Important: Do not return a sample to the fermenter unless all your test equipment has been sanitized.

Having this data not only gives you a second reference to completed fermentation, but it will also help you in sharing and duplicating your recipes.


Most Hydrometers are calibrated at 60*F to correct for temperature changes use the following table.

Temperature in degrees F* Specific Gravity Correction Example

Subtract .0005
Add .001
Add .002
Add .003
Add .005
Add .007
Temperature of must is 84*F.


Specific Gravity is 1.100

Corrective Figure (+) .003


Corrected Specific Gravity 1.103

Using a Hydrometer


To test your hydrometer, fill your hydrometer flask with distilled water at 60°F (most hydrometers are calibrated at this temperature). Float your hydrometer and spin it to free any clinging bubbles. Read the value on the hydrometer, record it, then check the temperature again (to ensure it is still at 60°F). Do this a few times and average the readings. This is your "offset", the amount above or below your hydrometer reading.

To take it even further, you can determine your own correction factor by heating the water sample by five or ten degrees at a time, taking gravity measurements, and then fitting a curve to your data.

To measure potential alcohol of your wine, two readings will be required. The first will be before fermentation commences, the second when fermentation stops. the second figure is to be subtracted from the first, the result is your alcohol percentage by volume.

1st. Reading 14%
2nd. Reading -1%
Alcohol Content 13%

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