One can easily and quickly determine the active ingredient concentration using a refractometer. Adherence to a specific active ingredient concentration significantly influences the operating behaviour of the cold lubricant.

As a rule, conventional or electronic hand refractometers are used for this. 

After adding 1-2 drops of sample and waiting for about 20 seconds (for temperature equalisation), one can see in a conventional hand refractometer a bright-dark boundary which is shown against a scale. One can read a refractometer value on this scale (as a rule, expressed as % Brix or refractive index). This refractometer value must be adjusted for temperature, as refractometric readings are strongly dependent on temperature. The temperature correction values must be calculated against the results. Then the measurement prism as well as the prism cover must be cleaned.

For an electronic, automatically processing hand refractometer, one needs only 1-2 drops of sample on the measurement prism and to press a button. About 3 seconds later, the already temperature-compensated results are digitally displayed. Thus one cannot incorrectly read a scale. In addition, refractometers are very reproducible, even for difficult samples such as emulsions. Commercial hand refractometers are difficult to read when testing emulsions, because there is seldom a sharp bright-dark boundary; rather, it is a border which can easily be misread. There is a frequent linear relationship between the refractometer value and concentration. Using a standards curve and correction factors for the various liquids being tested, one can determine a concentration value in volume-% (see Figure to the left). One can either create relevant standards curve oneself, or they are produced by the material’s supplier. Other industrial liquids can be tested with refractometers, such as liquids which are used for washing, etching and hardening.