Testing of Application and Dyeing Results
Hair dyes are tested directly on test subjects or in laboratory tests on hair strands. Trained hairdressers use the products to be tested in the salon and assess this directly following application as well as following several washings for important technical hairdressing parameters such as fragrance, consistency, spreadability, color depth, shade/color, coloration of scalp, coverage of gray hair, and evenness.
If hair coloring results of two products are to be compared directly in test subjects (half-head test), comparable tests must be performed previously on hair tresses. If these in vitro tests reveal no significant differences in color, the products can then be used in a half-head test.
In addition to hair dyes, eyebrow and eyelash dyes can also be tested. For this, comparative assessments are performed during half-head tests to determine the application properties and dyeing results of the products in our in-house climate-controlled salon.
To determine the lightening performance of bleaching agents, hair tresses are examined spectrophotometrically before and after a standardized bleaching.
The color permeation of hair dyes is measured by taking cross sections and subsequent image analysis.
- Nerenz, H, Huppmann, P, Schrader, K (2001). Computer-Supported Formulation of Oxidative Hair Dyes. Cosmet Toil 116(3), 55-59.