Viscosity
Definition
Viscosity is a fluid property that describes a fluids internal resistance to flow or deformation, and is one of the most important fluid properties to consider when designing a mixer. There are two common measures of viscosity, dynamic viscosity (µ) and kinematic viscosity (ν). The relationship between dynamic viscosity and kinematic viscosity is shown below:
ν – Kinematic viscosity (cSt)
µ – Dynamic viscosity (cP)
ρ – Density (g/cm3)
Dynamic viscosity is the most relevant to mixing applications as this describes the fluid resistance to flow under shear stress, whereas kinematic viscosity describes the resistance to flow under the pull of gravity.
Newtonian Fluids
In Newtonian fluids the dynamic viscosity is described as the ratio of the shear stress to the velocity gradient in a fluid. The viscosity remains constant through varying shear stress and over time, and the relationship is shown in the equation below:
τ – Shear stress
µ – Dynamic viscosity
du/dy – Velocity gradient
The majority of fluids can be modelled as Newtonian fluids and this is the type of fluid that we come across in the majority of mixing applications.
Non-Newtonian Fluids
Other types of fluid can exhibit non-Newtonian behaviour where the viscosity is not a constant value, and changes in response to some other variable.
Some of these are listed below:
- Pseudo-plastic or shear-thinning fluids are the most common type of non-Newtonian fluid that we encounter.
In these fluids the viscosity decreases with an increase in the shear stress applied. - Thixotropic fluids behave like pseudo-plastic fluids, except that the viscosity also decreases with time under shear stress.
- Dilatant and Preoptic fluids are the equivalent of pseudo-plastic and thixotropic fluids respectively,
except that their viscosity increases with shear rate and time respectively. - Viscoelastic fluids exhibit a combination of viscous and elastic properties when stressed.
This means that they behave partially like an elastic solid and have a tendency to revert back to their original shape after deformation. - Bingham plastics have a minimum shear stress required before any flow of the material will take place.
Some common non-Newtonian fluids are water based paints, polymer solutions, and many food and personal care products such as toothpaste and tomato ketchup.
Measuring Viscosity
Viscosity is measured with an instrument known as a viscometer, or rheometer, and there are multiple different types, the most common of which are explained below:

Falling Sphere Viscometer
The falling sphere type viscometers consist of a small sphere and a stationary glass tube filled with the fluid to be tested. The sphere is allowed to fall through the fluid and the time taken to pass between two points is measured. Using Stokes’ law the dynamic viscosity can then be calculated using the density of the fluid and sphere.
Viscosity Cups
Viscosity cups are a type of viscosity measuring device consisting of a cup with a precisely sized aperture in the base. The cup is filled with the liquid to be measured and the time taken for the liquid to drain from the cup through the aperture is taken. From this time value, the kinematic viscosity can be calculated using conversion formulas or tables provided by the manufacturer.
Viscosity cups are commonly used in the paints and coatings industries.

Rotational Viscometer
A more sophisticated type of rheometer is the rotational spindle type viscometer. These instruments work based on the Searle principle, where the torque required to rotate a spindle in each fluid at a certain speed is proportional to the fluid viscosity.
The speed of the rotating spindle can usually be varied which has the effect of varying the shear stress experienced by the fluid. This allows rotational viscometers to be used to measure the viscosity profile of non-Newtonian fluids which exhibit different viscosities at different levels of shear stress.

Category | Liquid | Specific gravity @ 16°C | Absolute viscosity (cP) | Temperature (°C) | Viscosity Type |
---|---|---|---|---|---|
Industrial Products | Acetate Glue | 1200 - 1400 | 20 | T | |
Industrial Products | Alcohol, sopropyl | 2 | Room Temp | ||
Industrial Products | Alkyd resins | 500 - 3,000 | Room Temp | ||
Industrial Products | Anti - freeze | 15 | Room Temp | ||
Food Products | Baby Food | 1400 | 93 | T | |
Food Products | Batter | 29500 | 30 | T | |
Food Products | Beer | 18 | Room Temp | ||
Food Products | Beet Sauce | 1950 | 76 | T | |
Industrial Products | Benzine | 5 | Room Temp | ||
Food Products | Biscuit Cream Premix | 29200 | 18 | T | |
Pharmaceuticals | Blood | 10 | Room Temp | ||
Fish & Animal Oils | Bone Oil | 0,92 | 48 | 54 | N |
Food Products | Brewers Yeast | 368 | 18 | T | |
Food Products | Broth Mix | 430 | 18 | T | |
Dairy Products | Butter Deodorised | 45 | 50 | N | |
Dairy Products | Butter Fat | 20 | 65 | N | |
Dairy Products | Butter | 30,000 | Room Temp | ||
Dairy Products | Butter cream, sour | 550 | Room Temp | ||
Food Products | Carob Bean Sauce | 1500 | 30 | T | |
Vegetable Oils | Castor Oil | 0,96 | 580 | 27 | N |
Industrial Products | Caulking compound | 5,000,000 - 10,000,000 | Room Temp | ||
Industrial Products | Caustic soda 50% | 45 | Room Temp | ||
Dairy Products | Cheese, soft | 30,000 | Room Temp | ||
Vegetable Oils | Chinawood Oil | 0,94 | 300 | 21 | N |
Food Products | Chocolate | 280 | 49 | T | |
Food Products | Chocolate syrup | 2,250 | Room Temp | ||
Food Products | Citrus Fruit Pulp | 1,27 | 600 | 20 | T |
Industrial Products | Cleaning emulsions | 1,500 | Room Temp | ||
Dairy Products | Cocoa Butter | 0,92 | 50 | 60 | N |
Vegetable Oils | Coconut Oil | 0,93 | 55 | 24 | N |
Fish & Animal Oils | Cod Oil | 0,93 | 32 | 38 | N |
Food Products | Coffee Liquor 30-40 | 10 - 100 | 20 | T | |
Dairy Products | Condensed Milk | 40 - 80 | 40-50 | N | |
Dairy Products | Condensed Milk 75 Solids | 1,3 | 2160 | 20 | T |
Vegetable Oils | Corn Oil | 0,92 | 28 | 57 | N |
Food Products | Corn syrup | 15,000 | Room Temp | ||
Dairy Products | Cottage Cheese | 30000 | 18 | T | |
Vegetable Oils | Cotton Seed Oil | 0,88 | 62 | 24 | N |
Dairy Products | Cream 30 Fat | 1 | 14 | 16 | N |
Dairy Products | Cream 45 Fat | 0,99 | 48 | 16 | N |
Dairy Products | Cream 50 Fat | 0,98 | 112 | 16 | N |
Dairy Products | Cream 50 Fat | 55 | 32 | N | |
Dairy Products | Cream, cheese | 100,000 | Room Temp | ||
Dairy Products | Cream, clotted | 20,000 | Room Temp | ||
Dairy Products | Cream, double | 120 | Room Temp | ||
Dairy Products | Cream, single | 50 | Room Temp | ||
Dairy Products | Cream, sour | 15,200 | Room Temp | ||
Industrial Products | Cresol Crystals | 10 | 18 | T | |
Food Products | Custard | 1,6 | 1500 | 85-90 | T |
Pharmaceuticals | Detergents | 1470 | 70 | T | |
Industrial Products | Diesel | 14 | Room Temp | ||
Glycol Products | Diethylene | 1,12 | 32 | 21 | N |
Industrial Products | Dipropyleneglycol | 107 | Room Temp | ||
Food Products | Edible Oil | 0,9 | 65 | 20 | N |
Industrial Products | Epoxy resin | 5,000 - 10,000 | Room Temp | ||
Glycol Products | Ethylene | 1,12 | 18 | 21 | N |
Glycol Products | Ethylene glycol | 16 | Room Temp | ||
Food Products | Fruit Juice | 1,04 | 55-75 | 18 | N |
Fuel & Lubricating Oils | Fuel oil no 4 | 12 | Room Temp | ||
Food Products | Gelatine 37 Solids | 1190 | 43 | T | |
Food Products | Gelatine | 1,200 | Room Temp | ||
Food Products | Glucose | 1,3 | 4300 - 8600 | 25-30 | T |
Industrial Products | Glue, gun grade | 5,000 - 50,000 | Room Temp | ||
Industrial Products | Glue, pourable | 3,000 - 5000 | Room Temp | ||
Industrial Products | Glycerine 100 | 1.26 at 20°C | 648 | 20 | N |
Pharmaceuticals | Glycerine | 1,000 - 2,000 | Room Temp | ||
Glycol Products | Glycol | 20 | Room Temp | ||
Food Products | Gravy Slurry | 1 | 110 | 80 | T |
Pharmaceuticals | Hand cream | 8,000 | Room Temp | ||
Pharmaceuticals | Hand lotion | 5,000 | Room Temp | ||
Food Products | Honey | 1,800 - 3,000 | Room Temp | ||
Fuel & Lubricating Oils | Hydraulic oil | 30 - 120 | Room Temp | ||
Food Products | Icing | 10,000 | Room Temp | ||
Industrial Products | Ink, printing, liquid | 550 - 2,200 | Room Temp | ||
Industrial Products | Isopropyl Alcohol | 1,11 | 1,9 | 85 | N |
Food Products | Jam Garnish | 8440 | 16 | T | |
Food Products | Jam | 8,500 | Room Temp | ||
Industrial Products | Kerosene | 10 | Room Temp | ||
Industrial Products | Lacquer 25 Solids | 3000 | 18 | T | |
Paints & Varnishes | Lacquer, water - based | 900 | Room Temp | ||
Paints & Varnishes | Lacquers 25% pigments | 3,000 | Room Temp | ||
Fish & Animal Oils | Lard | 0,96 | 62 | 38 | N |
Fish & Animal Oils | Lard Oil | 0.91-0.93 | 40 - 47 | 38 | N |
Pharmaceuticals | Latex Emulsion | 1 | 200 | 24 | T |
Paints & Varnishes | Latex neoprene | 5,000 | Room Temp | T | |
Paints & Varnishes | Latex paint | 750 | Room Temp | T | |
Vegetable Oils | Linseed Oil Raw | 0.93-0.94 | 29 | 38 | N |
Vegetable Oils | Linseed oil | 30- 70 | Room Temp | ||
Pharmaceuticals | Liquid soap | 85 | Room Temp | ||
Fuel & Lubricating Oils | Lubricating oil | 60- 200 | Room Temp | ||
Fuel & Lubricating Oils | Machine oil, heavy | 600 | Room Temp | ||
Fuel & Lubricating Oils | Machine oil, light | 150 | Room Temp | ||
Food Products | Malt Extract | 1,4 | 3000 | 60 | T |
Food Products | Malt Extract 80 | 9500 | 18 | T | |
Food Products | Maple syrup | 150 - 300 | Room Temp | ||
Food Products | Mayonnaise | 5,000 - 20,000 | Room Temp | ||
Industrial Products | Methyl ethyl ketone | 4 | Room Temp | ||
Dairy Products | Milk | 1.02-1.05 | 2 | 18 | N |
Dairy Products | Milk Whey 48 Sugar | 800 - 1500 | 40 | T | |
Dairy Products | Milk condensed | 6,000 | Room Temp | ||
Dairy Products | Milk evaporated | 6,100 | Room Temp | ||
Food Products | Mincemeat | 100000 | 30 | T | |
Food Products | Molasses | 5,000 - 10,000 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 10 | 50 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 20 | 125 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 30 | 200 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 40 | 320 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 50 | 540 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 60 | 1,000 | Room Temp | ||
Fuel & Lubricating Oils | Motor oil SAE 70 | 1,600 | Room Temp | ||
Food Products | Mousse Mix | 1200 | 5 | T | |
Industrial Products | NaOH 20 | 1,22 | 1 | 18 | N |
Industrial Products | NaOH 30 | 1,33 | 1 | 18 | N |
Industrial Products | NaOH 40 | 1,43 | 20 | 18 | N |
Vegetable Oils | Oleic acid | 40 | Room Temp | ||
Vegetable Oils | Olive Oil | 0,91 | 40 | 38 | N |
Food Products | Orange Juice Concentrate | 30 Brix | 630 | 20 | N |
Paints & Varnishes | Paint, water based | 2,400 | Room Temp | ||
Vegetable Oils | Palm Oil | 0,92 | 43 | 38 | N |
Food Products | Pancake batter | 2,200 | Room Temp | ||
Pharmaceuticals | Paraffin Emulsion | 1,2 | 3000 | 18 | T |
Industrial Products | Paraffin | 10 | Room Temp | ||
Vegetable Oils | Peanut Oil | 0,92 | 38 | 38 | N |
Food Products | Peanut butter | 150,000 - 250,000 | Room Temp | ||
Vegetable Oils | Peanut oil | 100 | Room Temp | ||
Food Products | Pectin | 300 | 38 | N | |
Industrial Products | Petrol, gasoline | 8 | Room Temp | ||
Pharmaceuticals | Petroleum jelly | 64,000 | Room Temp | ||
Industrial Products | Plastisol | 2,5 | 28000 | 18 | T |
Industrial Products | Polyester | 1.1 at 30 | 3000 | 30 | T |
Industrial Products | Polyester resin | 3,000 | Room Temp | ||
Industrial Products | Polyglycerine caprinate | 6,000 - 7,000 | Room Temp | ||
Industrial Products | Polyisobutylene | 1.09 at 85° | 12500 | 85 | T |
Industrial Products | Polymer solution | 20,000 | Room Temp | T | |
Industrial Products | Polyol, non - pigmented | 500 - 5,000 | Room Temp | ||
Industrial Products | Polypropylene | 240000 | 50 | T | |
Industrial Products | Potassium hydroxide | 67 | Room Temp | ||
Industrial Products | Printers Ink | 550 -2200 | 38 | T | |
Dairy Products | Process Cheese | 30000 | 18 | T | |
Glycol Products | Propylene | 1,04 | 52 | 21 | N |
Industrial Products | Putty | 100,000,000 | Room Temp | ||
Industrial Products | PVA resin | 65,000 | Room Temp | ||
Industrial Products | Resin Solution | 880 | 24 | T | |
Industrial Products | Resin pourable | 880 - 975 | Room Temp | ||
Industrial Products | Resin solution | 7,100 | Room Temp | ||
Food Products | Rice Pudding | 10000 | 100 | T | |
Food Products | Salad Cream | 1300 -2600 | 18 | T | |
Food Products | Sauce - Apple | 1,1 | 500 | 80 | T |
Vegetable Oils | Sesame oil | 94 | Room Temp | ||
Pharmaceuticals | Shampoo | 3,000 - 5,000 | Room Temp | ||
Pharmaceuticals | Soap Arylan | 1.0 at 40°C | 630 | 60 | T |
Pharmaceuticals | Soap Solution | 1.03 at 60°C | 82 | 60 | T |
Food Products | Sorbitol | 1,29 | 200 | 20 | N |
Vegetable Oils | Soya Bean Oil | 0,93 | 60 | 24 | N |
Food Products | Soya Bean Slurry | 5000 -10,000 | 50-90 | T | |
Food Products | Spaghetti sauce | 1,000 | Room Temp | ||
Fish & Animal Oils | Sperm Oil | 0,88 | 24 | 38 | N |
Food Products | Starch solution 25% | 300 | Room Temp | ||
Food Products | Sugar syrup, sucrose | 1,210 | Room Temp | ||
Industrial Products | Sulphonic Acid | 1,04 | 125 | 30 | T |
Industrial Products | Titanium dioxide | 5,000 | Room Temp | ||
Industrial Products | Toluol | 6 | Room Temp | ||
Food Products | Tomato Ketchup | 1000 | 30 | T | |
Food Products | Tomato Paste 30 | 195 | 18 | T | |
Food Products | Tomato juice | 180 | Room Temp | ||
Food Products | Tomato ketchup | 1,000 | Room Temp | ||
Food Products | Tomato puree | 50,000 | Room Temp | ||
Food Products | Tomato sauce | 2,600 | Room Temp | ||
Pharmaceuticals | Toothpaste | 70,000 - 100,000 | 18 | T | |
Industrial Products | Triacetate Dope | 48,000 / 60,000 | 40 | T | |
Glycol Products | Triethylene | 1,12 | 40 | 21 | N |
Vegetable Oils | Turpentine | 0,86 | 2 | 16 | N |
Paints & Varnishes | Varnish | 320 | Room Temp | ||
Vegetable Oils | Vegetable oil | 40 | Room Temp | ||
Food Products | Vinegar | 12 - 15 | 20 | N | |
Pharmaceuticals | Wax | 0,9 | 500 | 93 | T |
Fish & Animal Oils | Whale Oil | 0,93 | 25 - 39 | 38 | N |
Dairy Products | Whey | 800 - 1,500 | Room Temp | ||
Dairy Products | Whole Egg | 150 | 4,5 | T | |
Food Products | Yeast Surry | 20 | 18 | T | |
Dairy Products | Yoghurt | 3,000 - 8,000 | Room Temp |
Kinematic Viscosity (cSt) Cup Type | 1 | 2 | 3 | 4 | 7.5 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 | 300 | 325 | 350 | 375 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 | 1250 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
‘Ultra Low’ Cup | 53 | 68 | 84 | |||||||||||||||||||||||||||||||||
Shell Cup #1 | 17 | 21.5 | 26 | 35 | 46 | 57 | ||||||||||||||||||||||||||||||
Shell Cup #2 | 18.3 | 22 | 30.4 | 39 | 47 | 56 | ||||||||||||||||||||||||||||||
Shell Cup #2.5 | 19 | 25 | 30 | 35.6 | 46.6 | 57 | ||||||||||||||||||||||||||||||
Shell Cup #3 | 18.6 | 22 | 28.6 | 35 | 42 | 48 | 55 | |||||||||||||||||||||||||||||
Shell Cup #3.5 | 17.5 | 20 | 24.6 | 29.2 | 34 | 38.4 | 43 | 47.8 | 59.4 | |||||||||||||||||||||||||||
Shell Cup #4 | 18 | 21 | 24 | 27 | 30 | 37 | 45 | 52 | 60 | |||||||||||||||||||||||||||
Shell Cup #5 | 16 | 20 | 24 | 28 | 32 | 36 | 40 | 44 | 48 | 52 | 56 | 60 | 64 | |||||||||||||||||||||||
Shell Cup #6 | 17.5 | 19 | 20.5 | 22.5 | 24 | 25 | 31.5 | 37.5 | 44 | 50 | 56.5 | 63 | 78 | |||||||||||||||||||||||
Zahn Cup #1 | 30.5 | 32 | 35 | 38 | 42 | 45 | 52 | 60 | 68 | |||||||||||||||||||||||||||
Zahn Cup #2 | 18 | 19 | 20 | 22.5 | 25 | 28 | 30 | 34 | 38 | 43 | 53 | 63 | 72 | |||||||||||||||||||||||
Zahn Cup #3 | 17 | 19.5 | 22 | 24.5 | 27 | 30 | 32 | 35.5 | 38 | 41 | 43 | 45 | 48.5 | 58 | 70 | |||||||||||||||||||||
Zahn Cup #4 | 17 | 18 | 19.5 | 21 | 22.5 | 24 | 26 | 28 | 30 | 32 | 38 | 45 | 51 | 54 | 65 | 70 | ||||||||||||||||||||
Zahn Cup #5 | 17 | 18.5 | 20 | 21 | 22.5 | 27 | 31 | 35 | 40 | 45 | 49 | 60 | ||||||||||||||||||||||||
Ford Cup #3 | 32 | 37 | 40 | 43 | 53 | 63 | 73 | 83 | 93 | 103 | 113 | 120 | 130 | |||||||||||||||||||||||
Ford Cup #4 | 20 | 22 | 25 | 28 | 35 | 40 | 48 | 55 | 62 | 70 | 76 | 82 | 90 | 98 | 103 | |||||||||||||||||||||
ISO Cup #4 | 26 | 33 | 39 | 46 | 53 | 60 | ||||||||||||||||||||||||||||||
DIN Cup #4 | 20 | 22 | 24 | 26 | 28 | 30 | 35 | 40 | 46 | 50 | 56 | 61 | 71 | |||||||||||||||||||||||
AFNOR Cup #4 | 20 | 22 | 24 | 26 | 28 | 30 | 35 | 40 | 46 | 50 | 56 | 61 | 71 | |||||||||||||||||||||||
Norcross Cup #1 | 31 | 36 | 40 | 53 | 70 | 87 | ||||||||||||||||||||||||||||||
Norcross Cup #2 | 19 | 23 | 28 | 34 | 45 | 55 | 67 | 76 | ||||||||||||||||||||||||||||
Norcross Cup #3 | 17 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 68 | 79 | |||||||||||||||||||||||||
Norcross Cup #4 | 18 | 22 | 27 | 32 | 36 | 40 | 44 | 48 | 53 | 57 | 61 | 65 | 68 | 85 | ||||||||||||||||||||||
Norcross Cup #5 | 20 | 22 | 26 | 31 | 36 | 41 | 45 | 50 | 62 |
Kinematic Viscosity (cSt) Cup Type | 1 | 2 | 3 | 4 | 7.5 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 | 300 | 325 | 350 | 375 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 | 1250 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
‘Ultra Low’ Cup | 53 | 68 | 84 | |||||||||||||||||||||||||||||||||
Shell Cup #1 | 17 | 21.5 | 26 | 35 | 46 | 57 | ||||||||||||||||||||||||||||||
Shell Cup #2 | 18.3 | 22 | 30.4 | 39 | 47 | 56 | ||||||||||||||||||||||||||||||
Shell Cup #2.5 | 19 | 25 | 30 | 35.6 | 46.6 | 57 | ||||||||||||||||||||||||||||||
Shell Cup #3 | 18.6 | 22 | 28.6 | 35 | 42 | 48 | 55 | |||||||||||||||||||||||||||||
Shell Cup #3.5 | 17.5 | 20 | 24.6 | 29.2 | 34 | 38.4 | 43 | 47.8 | 59.4 | |||||||||||||||||||||||||||
Shell Cup #4 | 18 | 21 | 24 | 27 | 30 | 37 | 45 | 52 | 60 | |||||||||||||||||||||||||||
Shell Cup #5 | 16 | 20 | 24 | 28 | 32 | 36 | 40 | 44 | 48 | 52 | 56 | 60 | 64 | |||||||||||||||||||||||
Shell Cup #6 | 17.5 | 19 | 20.5 | 22.5 | 24 | 25 | 31.5 | 37.5 | 44 | 50 | 56.5 | 63 | 78 | |||||||||||||||||||||||
Zahn Cup #1 | 30.5 | 32 | 35 | 38 | 42 | 45 | 52 | 60 | 68 | |||||||||||||||||||||||||||
Zahn Cup #2 | 18 | 19 | 20 | 22.5 | 25 | 28 | 30 | 34 | 38 | 43 | 53 | 63 | 72 | |||||||||||||||||||||||
Zahn Cup #3 | 17 | 19.5 | 22 | 24.5 | 27 | 30 | 32 | 35.5 | 38 | 41 | 43 | 45 | 48.5 | 58 | 70 | |||||||||||||||||||||
Zahn Cup #4 | 17 | 18 | 19.5 | 21 | 22.5 | 24 | 26 | 28 | 30 | 32 | 38 | 45 | 51 | 54 | 65 | 70 | ||||||||||||||||||||
Zahn Cup #5 | 17 | 18.5 | 20 | 21 | 22.5 | 27 | 31 | 35 | 40 | 45 | 49 | 60 | ||||||||||||||||||||||||
Ford Cup #3 | 32 | 37 | 40 | 43 | 53 | 63 | 73 | 83 | 93 | 103 | 113 | 120 | 130 | |||||||||||||||||||||||
Ford Cup #4 | 20 | 22 | 25 | 28 | 35 | 40 | 48 | 55 | 62 | 70 | 76 | 82 | 90 | 98 | 103 | |||||||||||||||||||||
ISO Cup #4 | 26 | 33 | 39 | 46 | 53 | 60 | ||||||||||||||||||||||||||||||
DIN Cup #4 | 20 | 22 | 24 | 26 | 28 | 30 | 35 | 40 | 46 | 50 | 56 | 61 | 71 | |||||||||||||||||||||||
AFNOR Cup #4 | 20 | 22 | 24 | 26 | 28 | 30 | 35 | 40 | 46 | 50 | 56 | 61 | 71 | |||||||||||||||||||||||
Norcross Cup #1 | 31 | 36 | 40 | 53 | 70 | 87 | ||||||||||||||||||||||||||||||
Norcross Cup #2 | 19 | 23 | 28 | 34 | 45 | 55 | 67 | 76 | ||||||||||||||||||||||||||||
Norcross Cup #3 | 17 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 68 | 79 | |||||||||||||||||||||||||
Norcross Cup #4 | 18 | 22 | 27 | 32 | 36 | 40 | 44 | 48 | 53 | 57 | 61 | 65 | 68 | 85 | ||||||||||||||||||||||
Norcross Cup #5 | 20 | 22 | 26 | 31 | 36 | 41 | 45 | 50 | 62 |
Effect on Mixing
A fluids viscosity is one of the most important considerations when designing a mixer for a given application.
The greater a fluids viscosity, the more energy input is required to mix the fluid, and this means larger impellers, and more powerful motors to turn them. For highly viscous materials it may be necessary to use a close clearance type impeller, such as a gate or spiral type impeller, to achieve adequate mixing across the full tank volume.
Laminar & Turbulent Mixing
Mixing at low viscosity almost always takes place under turbulent conditions.
This means that mixing is controlled by inertial forces rather than by molecular diffusion, and mixing is achieved by the many eddies and vortices created by the mixer impeller.
Impellers such as the hydrofoil and pitched blade turbine type impellers are used for low viscosity mixing as they provide large pumping capacities and create large amounts of turbulence in the mixing vessel.
On the other hand, mixing at high viscosities takes place mainly in the laminar flow regime where the viscous forces dominate, damping down any turbulence, and molecular diffusion is the main source of mixing. To aid the molecular diffusion the aim of mixing in the laminar regime is to “cut and fold” the fluid so that there is greater interfacial area between the different fluids for the diffusion to take place.
Here, gate or screw type impellers are used as the large surface area
presented to the fluid helps to increase the “cutting and folding” action
across the entire tank volume.
The below plot shows the suitable viscosity ranges for various types of standard impellers.
Plot of Impeller Types vs Their Suitable Operating Viscosities

Non-Newtonian Mixing
Achieving adequate mixing in non-Newtonian fluids can be challenging. If you have a non-Newtonian mixing application and you require assistance in selecting a suitable agitator, please get in touch and one of our application engineers will be happy to help.
Static Mixers

The effect of viscosity on mixing in an inline static mixer is like the effects on stirred tank mixers. For lower viscosity applications the mixing is dominated by turbulent eddies, whereas higher viscosity applications are still dominated by molecular diffusion and rely on the same “cut and fold” method of mixing as stirred tank mixers described above.

Different types of mixing element are used for low and high viscosity fluids and generally follow the same principles as stirred tank impellers. The higher the viscosity, the larger and more complex the mixer elements placed in the pipe to ensure mixing across the entire pipe diameter, and this increases the pressure drop across the mixer. This increases the power required from the pump so, as in stirred tank mixers, more power is required for mixing high viscosity fluids.

John Whittle MEng (Hons)