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Wettability of hair

Contact angle as a measure for the effect of hair-care products

Hair-care products are made for specific applications and adapted for different hair types. At every application step, the care product encounters a certain surface character of the hair and leaves the surface changed. Our measuring instruments enable the surface of bunches of hair or even individual hairs to be analyzed. They therefore help to match the product specifically to the particular nature of the hair or application.

Measuring wettability using the single fiber method

Human hair is enclosed by a hydrophobic protective layer. The expectation when washing their hair is to remove contamination, which is also hydrophobic, but to leave the hair protected and durable again. Hair conditioners in turn change the surface by enclosing it in a smoothing coating.

The success of a hair-care application and the change to the surface are measured by means of the wettability of the hair before and after the application with the help of single-fiber contact angle technology. Our single-fiber Force Tensiometer – K100SF is fitted with a highly sensitive force sensor which is capable of detecting the small changes in the wetting forces before and after the application of a care product.

Optical contact angle measurements on hair

Optical contact angle measurements with drops in the picoliter range using our Drop Shape Analyzer – DSA100M instrument provide an alternative method for investigating wettability. These droplets are applied to the approximately 0.1 mm thick hair and subjected to drop shape analysis. At the same time, the microscope lens also makes rough and inhomogeneous regions of the hair visible.

KRÜSS Application Reports

AR206: Contact angle determination by the 'straw' method and packed cell method

An alternative to single fiber contact angle measurement on hair is the measurement of fiber bundles. Possible measurement errors due to very low wetting forces, irregular fiber diameters or curling at the surface are minimized here.

AR101: Evaluating Silicone Hair Treatment

Single fiber contact angle measurements are carried out with different silicones on dry, bleached hair. A comparison of several immersion cycles shows the different adsorption of the silicones onto the hair.

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