If the densities of the polymer solution and the solvent are very close one to the other, then the ratios below are equal:
For an experiment with a capillary viscometer, the viscometer is filled with the solvent (used to dissolve the polymer), and the drain time is measured. The drain time, t0, is the time necessary for the liquid level to move between the upper mark on the tube, and the lower mark on the tube.
The experiment is then repeated, filling the viscometer with the polymer solution, and measuring the drain time, t.
