Viscosity is a measure of how hard it is to force a substance into flow. How well a substance flows depends on the ability of the molecular layers of the substance to move in relation to one another. The speed at which the layers move is called shear rate.

Several factors affect the viscosity of a product. Temperature, type and amount of force, and time in flow are perhaps the three most important of these factors.

#### Temperature

Viscosity always changes with changes in a product's temperature. For some products, this variability can be more drastic (i.e. small changes in temperature equal big changes in viscosity). For others, the variability can be minimal. It is, however, always important to note the temperature of a product in relation to the viscosity measurement.

#### Force

In a discussion about viscosity, this concept is also known as shear stress. Sheer stress is the amount of force required to physically move or distribute molecular layers of a fluid in relation to one another. In a kinematic viscosity measurement, this force is gravity. In a dynamic viscosity measurement, the force is generated by something external (i.e. a spindle).

#### Time

Kinematic viscometers measure the time it takes for gravity to work on a substance. For instance, some kinematic viscometers test how long it takes for a fluid in one capillary to flow into another capillary. Others measure how long it takes for an object to fall a certain, defined distance within the substance. These viscometers are generally used for measuring Newtonian fluids, which only change viscosity with changes in temperature.

When dealing with dynamic viscosity one is usually testing non-Newtonian fluids, which are affected by more than changes in temperature. The amount of force exerted on the substance to induce flow and the amount of time for which that force is exerted can both affect the viscosity of the substance.

## Viscometers

### How it works

At Scientific Gear we offer two types of viscometers that are used to measure dynamic viscosity.

Rotational Viscometers measure the torque required to turn a spindle in a sample at a set speed. Electro Magnetic Spinning Viscometers generate a magnetic field that moves a small sphere within the sample.

### Choose the right Viscometer instrument for you

Our rotational viscometers are capable of measuring a wide viscosity range in one instrument with a variety of spindles. These sturdy, touch-screen instruments are easy to use and can be adapted to measure the viscosity of almost any product. They are capable of measuring Newtonian products, but are the more obvious choice for those with non-Newtonian products.

The electro magnetic spinning viscometer is an excellent choice for those who need to test with an extremely small sample size, ensure sterility during testing, or prevent cross-contamination. It can also be a good choice for those who need to test volatile, toxic, or air-sensitive products.