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Viscosity Standards for Zahn, Shell, and Ford Cups

Equations for conversion of kinematic viscosity or viscosity into other viscometric units are given here. All data must be at 25°C. Note that the equations apply only between the minimum and maximum drain times shown.

While the equations in the table below are widely used, the equation v = at - b/t is often more applicable, especially at low flow times and low kinematic viscosity.





Viscosity Standard
Kin Vis mm2/s (cSt/s)
Zahn Cup
Shell Cup
Ford Cup
Size
Drain time, sec
Size
Drain time, sec
Size
Drain time, sec
C6

9727-W10

Qty
8.9
-
-
1
52
-
-
C10

9727-W12

Qty
17
1
45
2
35
1
70
C20

9727-W15

Qty
34
1
60
2

64

40

2

-

42

-

C35

9727-W20

Qty
66
2
33

3

74

46

32

2

3

-

64

35

-

C60

9727-W25

Qty
120
2
48

4

57

36

3

4

58

36

C100

9727-W30

Qty
230
3

4

27

21

4

5

68

36

4

-

64

-

C200

9727-W35

Qty
460
3

4

47

36

5

6

72

29

5

-

40

-

C350

9727-W40

Qty
850
4

5

62

37

6

-

53

-

5

-

70

-

C600

9727-W45

Qty
1600
5
70
-
-
-
-



Ranges of Viscosity Cups


Cup Number

Equations* where
t = Time of flow, seconds
v = kinematic viscosity, mm2/s
Drain time seconds
Kinematic viscosity centistokes
min
max
min
max
Zahn Cups (See ASTM D 4212)
1
v = 1.1 (t – 29)
35
80
5
60
2
v = 3.5 (t – 14)
20
80
20
250
3
v = 11.7 (t – 7.5)
20
80
100
800
4
v = 14.8 (t – 5)
20
80
200
1200
5
v = 23t
20
80
400
1800
Shell Cups (See ASTM D 4212)
1
v = 0.226 (t – 13)
20
80
2
20
2
v = 0.576 (t – 5)
20
80
10
50
v = 0.925 (t – 3)
20
80
20
80
3
v = 1.51 (t – 2)
20
80
30
120
v = 2.17 (t – 1.5)
20
80
40
170
4
v = 3.45 (t – 1)
20
80
70
270
5
v = 6.5 (t – 1)
20
80
125
520
6
v= 16.2 (t – 0.5)
20
80
320
1300
Ford Cups (See ASTM D 1200)
1
v = 0.49 (t – 35.0)
55
100
10
35
2
v = 1.44 (t – 18.0)
40
100
25
120
3
v = 2.31 (t – 6.58)
20
100
49
220
4
v = 3.85 (t – 4.49)
20
100
70
370
5
v = 12.1 (t – 2.00)
20
100
200
1200
* While the equations in this table are widely used, the equation v = at - b/t is often more applicable, especially at low flow times and low kinematic viscosity.