The definition of "Viscosity" is the resistance to flow of a liquid (normally).A high viscosity means that the liquid will not flow easily - imagine treacle.
A low viscosity means that the liquid flows very easily - imagine water or gasoline.A viscometer is a device for testing the viscosity.
Viscosity is a fundamental property and has units of mm2/s, or mPa.s, depending on the measurement tactic employed. Temperature has a big influence on the viscosity of a liquid. When the temperature is lowered the viscosity increases. That is why your car engine labours and doesn't start as well in the cold winter months - the oil is more viscous when it is cold.
Viscosity is measured in so many different places - the obvious one is in the petroleum industry where lubricating oil, fuel oil, diesel, jet fuel and bitumen are routinely tested. This is just the tip of the ice berg - think about paints, coatings, sauces, soups etc -really the list is endless.
To measure viscosity you can use a glass capillary viscometer - like the one shown.
If you want more information about how to use a glass capillary viscometer then consult ASTM D 445 or ISO 3104.
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