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A Zahn cup is a 
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''.
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inter ...
measurement device widely used in the paint industry. It is commonly a stainless steel cup with a tiny hole drilled in the centre of the bottom of the cup. There is also a long handle attached to the sides. There are five cup specifications, labelled Zahn cup #x, where x is the number from one through five (see table below). Large number cup sizes are used when viscosity is high, while low number cup sizes are used when viscosity is low. They are manufactured in accordance to ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
D 4212, ASTM D1084 and ASTM D816
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 tokinematic viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inter ...
by using an equation for each cup specification number, where ''t'' is the efflux time and ''ν'' is the kinematic viscosity in centistokes
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inter ...
.
*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'' = 23''t''
Note the above equations are for a Brookfield series of Zahn cups.
Gardco signature Zahn cups and Gardco EZ Zahn cups use different conversions.
Ascott Zahn Cups are based on measuring the Flow of liquid in seconds. Results should be reported in Zahn-Seconds at a specified temperature for a particular cup.
To convert Zahn-Seconds to centistokes, refer to ASTM D4212, D816, and D1084
Centistokes ×Specific Gravity= Centipoise
See also
* Stormer viscometer *Ford viscosity cup
The Ford viscosity cup is a simple gravity device that permits the timed flow of a known volume of liquid passing through an orifice located at the bottom. Under ideal conditions, this rate of flow would be proportional to the kinematic visco ...
*Flow cups Flow cups are designed to accurately measure the viscosity of paints, inks, varnishes and similar products.
The process of flow through an orifice can often be used as a relative measurement and classification of viscosity.
This measured kinematic ...
References
*{{cite book , last = Patton , first = Temple C. , year = 1979 , title = Paint Flow and Pigment Dispersion , edition = 2nd , publisher = John Wiley & Sons Inc , isbn = 0-471-03272-7 Viscosity meters