by Charlotte Mellis on December 26, 2021

This is a brief and general outline of the method that is recommended to obtain accurate results from your hydrometer.

More detailed information is available from one of the standards that the hydrometers are made to, eg. AS2026, ISO650 etc.
Ensure that the hydrometer, the vessel, and the liquid are clean, and that the liquid is at a stable temperature. Insert the hydrometer into the liquid by holding the top of the stem, and releasing it when it is judged to be in equilibrium with the liquid. Press the hydrometer down a few millimeters and let it rise to the equilibrium point. Ensure that a good meniscus is formed.

For hydrometers calibrated at the bottom of the meniscus.

The scale should be viewed from below the surface of the liquid, and the observers eye raised until it is as close as possible to the plane of the liquid surface. You should see an ellipse reducing to a line as the eye is raised. Note reading. Apply appropriate corrections.

For hydrometers calibrated at the top of the meniscus.

Take the reading at the top of the meniscus formed on the stem of the hydrometer. Note reading. Apply corrections.

Note: Hydrometers calibrated to be read at the top of the meniscus usually have this noted on the hydrometer.