Viscosity Calculator V 1.04        Copyright © 2021 Henning Umland

It is a frequent task in the lubricant or plasticizer industry to adjust the viscosity of a formulation by blending two base liquids, A and B, with the viscosities ηA and ηB, respectively. Assuming the viscosities of both components are constant, one can do a concentration series and use the results to set up a table or graph showing the mass ratio required to obtain a blend with the desired viscosity. However, things get more complicated if the viscosities of the pure components are subject to variations, e. g., due to poor batch-to-batch uniformity, since viscosities of blends can not be found by linear interpolation.

In many cases, the relationship between the dynamic viscosity, η, of a homogeneous blend of two newtonian liquids and the concentrations of the components can be described fairly accurately by the equation

ηc = a + b · xB

B be the liquid with the higher viscosity. xB is the mass fraction of B in the blend. a, b, and c are material constants for the chosen combination. To find these, the viscosity of a test blend of A and B has to be measured. A concentration of roughly 50 (30...70) mass-% B in the test blend is recommended for best accuracy.

This program calculates the composition of a blend of two liquids as a function of the dynamic or kinematic viscosities of the components, the viscosity of a test blend of both, and a chosen target viscosity (all measured at the same temperature!). Therefore, it is a useful tool for process control in the chemical industry.

All common units for viscosity measurement can be used but remember to use the same unit for every measurement and perform all measurements at the same temperature..

The method requires the components to be completely miscible with each other over the entire concentration range. Phase separation, micelle formation (which often occurs in the presence of surfactants/emulsifiers) or gelation must not occur at any mass ratio.

With some homogeneous mixtures, e.g., the water/ethanol system, the viscosity-concentration curve passes through an extremum which makes predictions with this method impossible. Best results are obtained when the components are chemically similar to each other and show little interaction through hydrogen bonding. If in doubt, check the behavior of a system through a concentration series.

 Input Parameters:

Viscosity of pure component A: 
(liquid with lower viscosity)
    Viscosity of pure component B: 
(liquid with higher viscosity)
    Mass-% of B in test blend:      Viscosity of test blend:      Target viscosity: 

 Composition of Final Product:

Percentage of component A in final product: 
Percentage of component B in final product: 


This is experimental software. Although it has been thoroughly tested, it still may contain errors. The author assumes no responsibility for any damage resulting from the use of this program.