12.3 Two determinations of the kinematic viscosity of the
test material are required. For those viscometers that require a
complete cleaning after each flow time measurement, two
viscometers may be used. A single viscometer in which an
immediate, repeat flow time measurement can be made without
cleaning may also be used for the two measurements of flow
time and calculation of kinematic viscosity. Charge two viscometers
in the manner dictated by the design of the instrument.
For example, for the cross-arm or the BS U-tube
viscometers for opaque liquids, filter the sample through a
75 μm filter into two viscometers previously placed in the bath.
For samples subjected to heat treatment, use a preheated filter
to prevent the sample coagulating during the filtration.