How to Test Liquor With a Hydrometer

Place the narrow end of a funnel into the mouth of a hydrometer jar or 1,000 ml laboratory graduated cylinder.

Pour liquor into the funnel until the level of the liquor is within 1 inch of the top of the jar or graduated cylinder. Remove the funnel.

Hold a hydrometer by its narrow, scaled end and carefully lower it into the liquor-filled jar or cylinder. Take care not to drop the hydrometer; it may sink rapidly to the bottom and shatter.

Spin the hydrometer several times, still holding its narrow end between your fingers, to dislodge any air bubbles that might be clinging to the sides of the hydrometer. Clinging air bubbles will produce an inaccurate reading.

Gently release the hydrometer and wait for it to stop moving.

Identify the curve, called the meniscus, at the top of the liquor where the liquor rises up against the walls of its container and the neck of the hydrometer. Read the manufacturer instructions for your hydrometer and learn whether your hydrometer is designed to be read at the top or the bottom of the meniscus. Most hydrometers measure from the bottom of the meniscus.

Note where the meniscus of the liquor crosses the numbered scale on the narrow end of the hydrometer. Your eyes should be at the level of the meniscus when you do this. For example, you have a bottom-reading hydrometer and the bottom of the liquor meniscus crosses the scale of your hydrometer at 1.03.

Place a thermometer in the liquor and find the temperature of the liquor. Most hydrometers are calibrated to be accurate at 60 F. If your liquor is a different temperature, follow manufacturer instructions for adjusting your hydrometer reading according to the temperature you measure. For example, the instructions may require that you add 0.001 degree for every 5 degrees your fluid temperature is above 60 F. If your fluid is 70 F, therefore, you must find the difference between that temperature and 60, divide the difference by 5, multiply the result by 0.001 and add the answer to your hydrometer reading: [(70 - 60)/5] x 0.001 = 0.002, and 0.002 + 1.03 = 1.032. Your final reading is 1.032. This is the specific gravity of the liquor you are testing with your hydrometer.