After completing a batch of home-brewed beer, you probably are interested in finding out how much alcohol it contains. This can be done using a simple tool, called a hydrometer, that measures the density of water in relation to other ingredients in the beer. Home tools are not available to measure the alcohol content directly. But by doing some simple calculations, the alcohol content can be measured and you can feel safe consuming your homemade beer.
Take an initial reading with your hydrometer before the fermentation process begins. Sanitise the hydrometer and place it on a flat surface. Draw a sample of clean beer from the brewing container. Do not take any solid particles. Fill the test jar on the hydrometer 80 per cent full. The test jar should be slightly larger in diameter than your hydrometer.
Lower the hydrometer into the jar and spin it to release any bubbles that may be clinging to the sides of the jar or to the bottom of the hydrometer. When the hydrometer is floating in the jar without touching the edges of the container, take the reading. This is done by looking at the surface level of the liquid and reading the potential alcohol scale on the hydrometer. Record this measurement.
Take another reading after your beer is done fermenting. Follow the same procedure as before to take the reading. Subtract the potential alcohol reading after fermentation from the potential alcohol reading before fermentation. This number is the percentage of alcohol in your beer. For example, if the reading was 13 per cent before fermentation and 2 per cent after, your beer has an 11 per cent alcohol content.