Home Wine Making - How To Use A Hydrometer

For wine makers who are just getting started, you will often stumble upon wine-making instructions or guides which will require the use of a hydrometer. This unique device will likely confuse you as there is a high chance that no one has been aware of such device before - let alone understanding how to use it!

First off, we should explore the role. Why do you need a hydrometer in wine-making? The hydrometer will allow the wine maker to check the alcohol level of the wine. It measures the specific gravity of a fluid and by subtracting this reading pre and post fermentation, wine makers will be able to calculate the alcohol level of the wine they're making.

Before we move to reading the hydrometer, there's another fundamental concept to clear up - the specific gravity. Specific gravity is the ratio of the density of the compound to that of water. Hence, the specific gravity of water is going to be equal to 1.00 and specific gravity of fruit juice used in wine making are usually above 1.00 (approximately 1.07 to 1.09). The explanation for the larger specific gravity is because fruit juice contains sugar along with other substance added to it which makes it much denser than pure water. The specific gravity of alcohol is 0.787 which means it's less dense than water.

Keeping in mind the above mentioned concept, it becomes crystal clear how wine makers estimate the alcohol level. In the course of fermentation, sugar in the fruit juice is converted by yeast into alcohol. Since alcohol is significantly less dense than sugar and water the specific gravity of fruit juice will drop in the course of fermentation, and once this specific gravity stop decreasing, you know that fermentation has ended and all the sugar has been converted into alcohol.

We shall now look at how you will use and read a hydrometer. To start with, you will need to pour some of the fruit juice into the hydrometer and ensure that the bulb is floating without touching the base. Read off the scale. The reading probably will be around 1.07 to 1.09. Moreover, the hydrometer ought to come with its very own temperature correction chart and thus, you need to measure the temperature of the fruit juice and apply the correction value to the reading.

After 2-3 weeks of fermentation, take another reading by repeating the above procedure. If fermentation proceeded smoothly, the specific gravity ought to be below 1.00. Otherwise, you need to allow the wine some more time to continue fermenting.

To calculate the alcohol level, subtract the final reading from the initial reading and multiply it by 125. For example, the original reading of the fruit juice is 1.08 and the final reading of the wine (previously fruit juice) is 0.98. Subtracting 0.98 from 1.08 will give you 0.1 and multiplying that by 125 gives you 12.5% - which is the approximate alcohol level. For wine, the approximate range of alcohol level is 12.5% to 14.5%.