An Alcometer / Alcoholmeter (as apposed to a Wash, Wine & Beer Hydrometer) is used to test the strength of your spirit. Additives such as flavouring and Liquid Glucose will distort the hydrometer readings. Alcometers should only be used to test spirit before any additives such as flavouring or liquid glucose are mixed. The Alcometer is floated in the spirit to measure the alcohol content. As alcohol is thinner than water, the higher in strength the alcohol is, the further down the hydrometer floats. The reading is taken where the surface of the spirit cuts the scale of the hydrometer.