Properly measuring the alcohol content of homemade wine or beer requires the use of a device called a hydrometer. The hydrometer is a thin, glass tube filled with mercury or lead and has a scale imprinted on the side of it called the "potential alcohol" scale. To accurately determine the amount of alcohol a solution contains, you must take hydrometer measurements both before the fermentation process as well as after the fermentation process.
Fill a sink with 5 gallons of cold water and 2 ounces of bleach. Place the hydrometer, test tube and turkey baster into the water and let them soak for 10 minutes. Drain the sink and rinse the items with clean water. This process sanitizes the items and prevents potential contamination of the wine.
Insert a turkey baster into the juice solution before fermentation. Squeeze the bulb on the end of the turkey baster and then release it to suck up some of the juice. Do not allow any of the sediment to enter the turkey baster.
Squeeze the bulb on the turkey baster and release the liquid into a test tube, filling it 3/4 full of juice.
Place the hydrometer into the test tube and gently twist it between your fingers. This will remove any air bubbles trapped in the device.
Let go of the hydrometer and allow it to float. Move to the side of the glass and look at the hydrometer marker that is level with the surface of the water. This is the potential alcohol level. Write down the number for future reference.
Remove the hydrometer and discard the juice in the test tube. Allow the remainder of the wine mixture to ferment. This can take anywhere from two weeks to a month or more depending on the ingredients used.
Re-sanitize all of the equipment and then insert the turkey baster into the fermented solution. Squeeze the bulb and suck up the fermented solution.
Place the liquid into the test tube and then insert the hydrometer.
Twist the hydrometer to remove the air bubbles and then let it go. The hydrometer should sink lower than it did during the first reading.
Read the potential alcohol level, which is where the surface of the liquid meets the hydrometer.
Subtract the second potential alcohol reading from the reading measured before the fermentation process. The result is the actual alcohol content of the beverage.