I am carrying an experiment where I will be measuring the viscosity of honey using Zahn cup but I don't know what is the optimal and efficient size and the size of the opening to purchase if you can please help me? Thank you for your co-operation.
It depends on the viscosity of your honey, many honeys are too high viscosity for a typical Zahn test.
average honey has a viscosity of about 2000 centistokes and the biggest zahn cup, number 5 goes up to 1800 centistokes @ 80 seconds, if you buy cup number 5, you may find a few will go through it, so you have to find a higher viscosity method.
quote: When measured at 25 deg C viscosity of honey samples came within the range from 18169 to 2560 cP
there are lists of viscosity tests like dropping a sphere of a specific weight & density and see the time it takes the sphere to reach designated junctures or something.