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Glycerin Viscosity Measurement: Impact of Temperature and Concentration on Quality Control

Glycerin is a multifunctional compound used in a wide range of applications, including cosmetics, food, and pharmaceuticals. Among these, viscosity is one of the important properties of glycerin and plays an important role in quality control and product development.

Glycerin type and viscosity

Basic information on glycerol

Formula C3H8O3
Odor Odorless
Density 1.261 g/c㎥
Melting point 18℃
Boiling point 290℃

 There are various types of glycerin, including pure glycerin, aqueous glycerin, and vegetable glycerin, each with a different viscosity.

Picture explaining the formula of glycerin

 We will explain the derivation of the viscosity calculation formula.

Viscosity Definition: 

η = τ / 𝛾˙

  where 𝜂 is the viscosity, 𝜏 is the shear stress, and 𝛾˙ is the shear rate.

The units of viscosity are as follows.

  • ​Pa·s (pascal second)
  • cPs (centipoise)

 

Kinematic Viscosity Definition:

Kinematic viscosity is the viscosity divided by the fluid's density and is defined by the following equation:

 ν = η / 𝜌

where 𝜈 is the kinematic viscosity, 𝜂 is the viscosity, and 𝜌 is the density.

The units of kinematic viscosity are as follows:

  • St (stokes)
  • cSt (centistokes)

 100 cSt is 1 St.

 Related post: What is viscosity? It also introduces the units used in viscometers.|Rion viscometer online shop

 

Viscosity of pure glycerin

Pure glycerin is a colorless, odorless liquid with a viscosity of approximately 870 Pa·s (870,000 cP) at 20°C. As the temperature increases, the viscosity decreases, reaching approximately 450 Pa·s (450,000 cP) at 40°C.

 

Viscosity of glycerin water

Picture of viscosity of glycerin vs water

The viscosity of a glycerin water varies depending on the concentration of glycerin and the temperature. In general, the higher the glycerin concentration and the lower the temperature, the higher the viscosity.

 

Viscosity of vegetable glycerin

Vegetable glycerin is glycerin made from vegetable oils rather than animal fats. It has fewer impurities than pure glycerin, so it has a lower viscosity, about 650 Pa·s (650,000 cP).


[Temperature/Concentration/Purity] Three factors that determine the viscosity of glycerin

The viscosity of glycerin is determined by three factors:

Picture of viscosity of glycerin vs temperature

 
Temperature

As the temperature increases, the thermal motion of the glycerin molecules increases, making it more fluid and therefore less viscous.

The viscosity of glycerin at 20°C, 25°C, 30°C, and 40°C are as follows.

Temperature Viscosity (Pa·s) 
at 20℃ Approx. 870
at 25℃ Approx. 1000
at 30℃ Approx. 1200
at 40℃ Approx. 1700

The viscosity of glycerin at room temperature is 870 to 1700 Pa·s.

 

Concentration

As the glycerin concentration increases, the interactions between the glycerin molecules become stronger, reducing fluidity and therefore increasing viscosity. Below is a table of glycerin viscosities.

Glycerin concentration Viscosity at 20℃ (Pa·s) 
100% Approx. 870
50% Approx. 1200
25% Approx. 1700
10% Approx. 2500

 

Glycerin Viscosity Chart (vs. Temperature, vs. water)

Check out this chart to see how glycerin's viscosity varies with temperature and concentration.

Glycerin viscosity chart

Purity

The viscosity of glycerin is greatly affected by its purity. Below is a table of glycerin viscosities.

Purity  Viscosity at 20℃ (Pa·s) 
High Approx. 870
Medium Approx. 1000~1500
Low Approx. 1500~

  

Glycerin Viscosity FAQs

How to increase the viscosity of glycerin?

1. Lower the temperature
The viscosity of glycerin increases as the temperature decreases, so the easiest way to increase the viscosity of glycerin is to lower the temperature.

2. Increasing the concentration
The viscosity of a glycerin solution increases as the concentration of glycerin increases. Therefore, to increase the viscosity of glycerin, it is necessary to add water to decrease the concentration.

3. Use additives
Certain additives can increase the viscosity of glycerin. For example, the viscosity of glycerin can be adjusted by adding high molecular weight polymers or thickeners.

 

How to reduce the viscosity of glycerin?

1. Increase the temperature
The viscosity of glycerin increases as the temperature decreases, so the easiest way to increase the viscosity of glycerin is to lower the temperature.

2. Reduce the concentration
The viscosity of a glycerin solution increases as the concentration of glycerin increases. Therefore, to increase the viscosity of glycerin, it is necessary to add water to decrease the concentration.

3. Adding water
Certain additives can increase the viscosity of glycerin. For example, the viscosity of glycerin can be adjusted by adding high molecular weight polymers or thickeners.

 

Importance of glycerin viscosity measurement

Glycerin viscosity measurement plays an important role in quality control and manufacturing processes.

The role of viscosity measurement in production and quality control

The viscosity measurement of glycerin can grasp the following quality indicators.

  • Purity
  • Deterioration level
  • Moisture content
  • Amount of additives
  • Viscosity value
  • Dynamic viscosity
  • Viscosity coefficient

These indicators go a long way in stabilizing product quality.

 

Examples of quality control based on viscosity measurement

Measurement of glycerin viscosity contributes to quality control and efficient manufacturing processes in a variety of fields.
 

Cosmetics

The viscosity of cosmetics affects the feel when used, the finish, and storage stability. By adjusting the viscosity based on viscosity measurements, it is possible to produce high-quality cosmetics.

 

Food additives

The viscosity of food additives affects the texture and storage stability of food. By adjusting the amount and type of additive based on viscosity measurements, it is possible to produce high-quality food additives.

 

Pharmaceuticals

The viscosity of pharmaceuticals affects the dissolution rate and absorption rate of drugs. By adjusting the viscosity based on viscosity measurements, it is possible to produce safe and effective pharmaceuticals.

 
How to measure the viscosity of glycerin

Measuring the viscosity of glycerin plays an important role in quality control and manufacturing processes. 

 

Types of viscometer

The following viscometers are suitable for measuring the viscosity of glycerin.

Rotational viscometer

Rotational viscometer is the most common viscometer. It measure the resistance of a rotating rotor.

Advantages  High accuracy, wide range of viscosity measurements possible
Disadvantages Expensive, complicated operation

 

Falling Viscometer

Falling viscometer is a simple and inexpensive viscometer. It measures the time it takes for a certain amount of capsules to fall.

Advantages  Inexpensive, easy to operate
Disadvantages Low accuracy, not suitable for high viscosity measurement

The best way to measure the viscosity of glycerin is with a rotational viscometer.

 

For more information on the types of viscometers, see the following article:

 Related article:Introducing 8 types of viscometers|RION viscometer online shop

 

Glycerin viscosity measurement procedure

The viscosity of glycerin is measured by the following procedure.

  1. Place glycerin in a clean, dry container
  2. Place the sample in the viscometer
  3. Set measurement conditions
  4. Press the measurement button

 When measuring the viscosity of glycerin, the following points should be taken into consideration.

  • Keep the measurement temperature constant.
  • Avoid introducing air bubbles.
  • Interpret the results taking into account the measurement temperature and concentration.  

 

RION's viscometer is recommended for measuring viscosity!

RION logo

RION's viscometer is recommended for the following three reasons.

1.Confidence in accuracy

RION has a long history of manufacturing and developing viscometers. Utilizing our many years of knowledge and experience, we are able to achieve accurate viscosity measurements that are competitive with our competitors.

2.Portable type that can be measured anywhere

Most common viscometers are large and heavy. However, RION's VT-06 is compact and lightweight while maintaining measurement accuracy. The structure is simple, so even people with no knowledge or experience of viscosity measurement can easily measure it.

3.Loved by many customers around the world

RION is a Japanese manufacturer, but the viscometer VT-06 is used not only by customers in Japan but also by customers in countries around the world. VT-06 may be used for quality control in the things you usually use and eat.

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