Although not mandatory, for some transparent liquid
sample types such as viscous oils that are prone to having
entrained air or gas bubbles present in the sample, the use of an
ultrasonic bath (see 6.6) without the heater turned on (if so
equipped) has been found effective in homogenizing and
dissipating bubbles typically within 5 min prior to taking a test
specimen for analysis, with no material impact on results.
Charge the viscometer in the manner dictated by the design of
the instrument, this operation being in conformity with that
employed when the instrument was calibrated. If the sample is
thought or known to contain fibers or solid particles, filter
through a 75 μm screen, either prior to or during charging (see
Specifications D446).