A band viscometer is shown in Figure 2. It consists of two blocks with flat surfaces held apart by shims. There is a small well in the top in which the fluid or paste to be tested is placed. A tape of cellulose acetate is pulled between the blocks and the tape pulls the fluid or paste with it between the parallel faces of the blocks. In normal use weights are hung on the end of the tape and allowed to pull the tape and the material to be tested between the blocks. After it has reached terminal velocity, the time for the tape to travel a known distance is recorded. By the use of various weights, data for a force rate of shear graph can be obtained. The instrument used for this work was a slight modification of that previously described.

In this test a ** f tape was pulled between the blocks with a motor and pulley at a rate of ** f with a clearance of 0.002'' on each side of the tape. This gives a rate of shear of ** f. This, however, can only be considered approximate, as the diameter of the pulley was increased by the build-up of tape and the tape was occasionally removed from the pulley during the runs. The face of one block contained a hole 1 16'' in diameter which led to a manometer for the measurement of the normal pressure.

Although there were only four fluids tested, it was apparent that there were two distinct types. Two of the fluids showed a high positive normal pressure when undergoing shear, and two showed small negative pressures which were negligible in comparison with the amount of the positive pressures generated by the other two.