Zahn cup
Encyclopedia
A Zahn cup is a viscosity
measurement device widely used in the paint industry. It is commonly a stainless steel cup with a tiny hole drilled in the center of the bottom of the cup. There is also a long handle attached to the sides. There are five cup specifications, labeled Zahn cup #x, where x is the number from one through five. Use large number cup sizes when viscosity is high, use low number cup sizes when viscosity is low.
To determine the viscosity of a liquid, the cup is dipped and completely filled with the substance. After lifting the cup out of the substance the user measures the time until the liquid streaming out of it breaks up, this is the corresponding "efflux time".
On paint standard specifications, one denotes viscosity in this manner: efflux time, Zahn cup number.
Conversion
One can convert efflux time to kinematic viscosity by using an equation for each cup specification number, where t is the efflux time and ν is the kinematic viscosity in centistokes.
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
measurement device widely used in the paint industry. It is commonly a stainless steel cup with a tiny hole drilled in the center of the bottom of the cup. There is also a long handle attached to the sides. There are five cup specifications, labeled Zahn cup #x, where x is the number from one through five. Use large number cup sizes when viscosity is high, use low number cup sizes when viscosity is low.
To determine the viscosity of a liquid, the cup is dipped and completely filled with the substance. After lifting the cup out of the substance the user measures the time until the liquid streaming out of it breaks up, this is the corresponding "efflux time".
On paint standard specifications, one denotes viscosity in this manner: efflux time, Zahn cup number.
Conversion
One can convert efflux time to kinematic viscosity by using an equation for each cup specification number, where t is the efflux time and ν is the kinematic viscosity in centistokes.
- Zahn Cup #1: ν = 1.1(t - 29)
- Zahn Cup #2: ν = 3.5(t - 14)
- Zahn Cup #3: ν = 11.7(t - 7.5)
- Zahn Cup #4: ν = 14.8(t - 5)
- Zahn Cup #5: ν = 23t