How do you measure the viscosity of a non-Newtonian fluid?
Since Non-Newtonian fluids have a viscosity that changes with shear rate [as well as temperature like everything else], you have to specify that it is a viscosity measured at a given shear rate. You can specify something other than shear rate if it corresponds to a given shear rate. One type of viscometer uses a weight which is lowered on a string driving a paddle wheel. You time how long it takes the weight to drop a standard amount, ie, the time for the paddle wheel to make a certain number of rotations. Torque is proportional to the weight. If instead of a paddle wheel it has a cylinder, it is called a couette, but those are used for polymer melts and really viscous stuff like resins. Another approach is to put the fluid in a test tube but do not fill it all the way, cork it, then invert it and see how long the bubble takes to rise. Usually this method is used with several tubes having fluids of standard viscosity, so it is simply a question of which bubble in the standards rises as
