Friday, 23 April 2021, 6:41 PM
Site: IMI eLearning
Course: IMI eLearning (IMI eLearning)
Glossary: Automotive Glossary


The flow rate of a liquid. The addition of solvents and/or diluents will reduce the viscosity or fluidity of the paint. Paint viscosity must be carefully adjusted and controlled to allow proper atomisation and flow-out.

Viscosity cup

A precision device used to measure the viscosity of a liquid by timing how long it takes the liquid to drain out of the cup in a continuous stream. The standard Viscosity cup in use in the UK paint industry is known as a BS B4 or DIN 4 cup, which has a 4mm orifice for the paint to flow through.

Viscosity Index

A measure of the change in the flow rate (viscosity) of a liquid with temperature rise. The higher the viscosity index the smaller is the change in viscosity.

Viscous Coupling

A drive coupling that uses a fluid to transmit drive. Also sometimes a fluid coupling.

VOC Content

The measure of volatile organic compounds (VOC's) in solvent-borne paints. Usually measured as the weight in kilos of non-exempt solvent per tonne of paint.


Readily changes to vapour or gas at ambient temperatures.


The tendency of a liquid to evaporate. Liquids with high boiling points have low volatility and vice-versa. Volatility affects flash-off time and fire hazard consideration.


Electromotive force expressed in volts. Potential difference.

Voltage Drop

The voltage that is lost when an electrical current passes through a resistance.

Voltage Regulator

An electrical or electronic device to maintain a generator output within a narrow voltage range.