The density of a coating should remain constant from batch to batch. Also known as Density Cups or Specific Gravity Cups, Picnometers are used to determine the specific weight per unit volume of a liquid at a given temperature.

The Elcometer 1800 Specific Gravity Cup is a simple but effective instrument used to determine the density of paints and similar low or medium viscosity fluids. The instrument is sometimes known as a Densimeter, Picnometer or Pyknometer.

The instrument consists of a cylindrical container and a lid. The lid has a small hole at its centre through which excess air and liquid can escape.

The instrument allows the mass of a known volume of liquid to be measured and its density (or specific gravity) to be calculated.