Use a hydrometer to calculate the ABV, Alcohol by Volume, of wine. ABV is the standard way of expressing the amount of alcohol in wines expressed as a percentage.
A hydrometer measures the specific gravity of a liquid. If you know the specific gravity both before and after fermentation it is possible to calculate the per cent ABV.
- Skill level:
- Moderately Easy
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Things you need
- Clear flask
Pour enough unfermented liquid into the clear flask to allow the hydrometer to float freely. Measure the specific gravity by reading the figure against the scale on the hydrometer at the level of the top of the liquid. This figure is the original gravity (OG). Measure the temperature of the liquid too and take a note of both figures.
Ferment your wine for the period of time indicated in the recipe you are following.
Repeat step one to measure the specific gravity again once fermentation has finished. This figure is the final gravity (FG). Measure the temperature of the liquid again too and note both figures.
Standardise your figures for original gravity and final gravity to take account of differences in temperature as all hydrometers are calibrated to a specific temperature, typically 59 Fahrenheit. Use the Hydrometer Temperature Corrections table found at the link in the resources section below to compensate for differences in temperature. There are also online calculator tools to help correct your figures.
Calculate the per cent ABV by subtracting your adjusted final gravity from your original gravity, multiplying by 1000, then dividing by 7.36.
For example, if original gravity is 1.095 and final gravity is 1.008, multiply the difference (0.087) by 1000 (870) then divide by 7.36 to get an ABV of 11.8 per cent.
Tips and warnings
- Use the same hydrometer and thermometer for both the original gravity reading and the final gravity reading to ensure you get an accurate figure for per cent ABV.
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