Any remaining material in the cup needs to be removed by rinsing with a suitable solvent. Light naphtha, heptane, octane, highly aromatic solvents and/or any other petroleum derived hydrocarbon solvents can be used. Varsol® is a commercial solvent that works well for this purpose.
Dry the Viscosity Cup effectively with a lint-free cloth. Use a highly volatile solvent for the second wash, since any remaining hydrocarbon solvent from the first pass evaporates quickly after rinsing the sample from the cup. Hypersolve, MEK and Alcohol are available for aluminum mugs, and Hypersolve and Alcohol for stainless steel mugs. Acetone is often used as the second solvent because of its high volatility and ability to dissolve trace amounts of white spirit and water.
In the third method, a low flow of clean air is sufficient to evaporate any remaining traces of volatile solvents. Be careful to avoid rapid evaporation of these solvents, as this will cool the surface to the point where it may bring the moist air below the dew point, creating a film of water on the cup.
