Funnel Viscosity sec/qt
The Marsh Funnel is the field instrument used to measure viscosity. It is graduated so that one quart (946 cc) of water will flow through the funnel in 26 seconds. To run a test, the bottom orifice is covered and drilling fluid is poured over a screen until the funnel is full. When the bottom is uncovered, the time required to fill one quart is recorded (in seconds) along with the temperature.
Funnel viscosity is a rapid, simple test, but because it is a one point measurement it does not provide information as to why the viscosity has changed, only that it has changed.
