Some experiments that test the viscosity of liquids are the marble race experiment and the liquid race experiment. For the marble race experiment, you need a tall graduated cylinder, a marble, a stopwatch and the various liquids to test. For the liquid race experiment, you need a ramp, the liquids to test, and a stopwatch or tape measure.
To conduct the marble race experiment, fill the graduated cylinder with one of the liquids to a level a few centimeters below the top. Once full, simultaneously drop the marble into the liquid as you start the stopwatch. Stop the stopwatch when the marble gets to the bottom of the cylinder. Record the name of the liquid you used and the time it took for the marble to get to the bottom of the cylinder. Repeat two more times, ensuring you fill the cylinder up to the same level each time. Find the average time for the three runs, and repeat the procedure for the other liquids.
For the liquid race experiment, tip each liquid at the top of the ramp, and record the amount of time it takes each to get to the bottom. As with the marble race experiment, repeat the procedure two more times for each liquid, record the results, and find the mean of the three times.