A hydrometer measures the specific gravity (SG) or weight of liquid compared to water. It is a glass instrument with a long thin neck and a bulbous bottom that is used to measure the amount of sugar in the working wine mixture, which is called "must." The instrument floats in liquid and is read by a scale inside the thin glass tube. Typically, hydrometer readings are taken through out the fermentation process, and are recorded in order to monitor the amount of sugar converted into alcohol.
Instructions
1. Pour off enough wine or must into the sanitized quart jar so it is approximately 80 percent full. Be sure the liquid is clear and does not contain any solids, otherwise this will give a false reading. Hydrometers are calibrated to be used in liquids that range between 59 to 60 degrees Fahrenheit.
2. Set the glass hydrometer into the wine and spin the bulb gently between fingers. This will remove any air bubbles that are clinging to the bottom. Air bubbles also will give a false reading.
3. Let the hydrometer to come to rest on its own. Read the scale at the intersection point of the liquids surface to the interior scale. Observe the scale head on and not an angle. The surface tension of the liquid can give a false reading if the scale is read at any angle other than a straight line reading. Record this measurement.
4. Test the wine in small quantities every week until it reaches the correct fermentation level.
5. Pure water will have a reading of 1.000. Begin reading the records as the first scale will be in the neighborhood of 1.046. This corresponds to 1 lb. of sugar dissolved in 1 gallon of water. Over time, the specific gravity will change as the alcohol begins to develop. The final reading will be in the area of 1.090. This is the "magic" number for winemakers as wine is preserved best at this percent of alcohol content.
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