The pycnometer (from the Greek πυκνός (piknos), "dense") is a tool used to define the density of a material. Density is the ratio of the mass to the volume of the sample.

It is a small metal cylinder of known volume (about 100 cm3) that is filled with the suspension sample (grit, glaze, engobe, ceramic slip, etc) and that determines the relationship between mass and volume. The study of density values returns a fundamental data being one of the key parameters to be checked along the production line. The higher the density, the higher the solid content of the ceramic suspension.

The empty pycnometer is weighed first and the weight is recorded.

The volume of the pycnometer (which is known) is filled with the liquid whose density value is unknown. It will be easy to get the density of the fluid by dividing the weight of the liquid that is in the pycnometer by its volume.