Ever wondered what a hydrometer is, or how you use it? Richard shows you just how straight forward it really is to use this essential piece of equipment.
Download your copy of our hydrometer instruction guide here:
A hydrometer is a truly essential piece of equipment when making wine, beer, cider or spirits. It’s purpose is to measure the Specific Gravity (SG) of the liquid.
Measuring Specific Gravity is crucial as this tells you how much sugar is in your fermentation. Why is this useful? This information will help you set the right sugar level at the start (to ensure a good fermentation. It will also tell you when the fermentation is finished, and best of all, with a start reading and an end reading, you can calculate the Alcohol by Volume (ABV) percentage.
For example the start gravity in a typical wine will be 1.075 to 1.090 (a lot of instructions will leave out the point and just say 1090 for example). This will change on a daily basis by about 10 points but this does depend on temperature and nutrition. After a few days the gravity will have typically dropped to 1.040 and will finish in the region of 1.000 to 0.990.
How does it work?
It will measure the amount of sugar in the liquid. The more sugar in the liquid, the higher the reading. The more alcohol there is in the liquid the lower the reading (that is after fermentation as the sugar has now been converted into alcohol). For example, if the hydrometer is placed water at 20°C, it will read 1.000. This is always useful to know as you can test your hydrometer. In essence, the denser the liquid (the more sugars in it); the higher gravity reading.
How do I calculate ABV?
If you’ve noted down your starting specific gravity, and your final specific gravity then you can calculate your ABV, which is the figure we’re all interested in! Simply take the difference between the two values and divide by 7.362.
For example, when making a wine if our starting point is 1.080 and our finishing point is 0.990, the difference would be 90 points. Dividing this by 7.362 gives us 12.22% ABV. This would be right in the region we’re looking to achieve.