The Dove and TreSemme brand owner has developed a method of assessing hair colour changes which occur in oxidatively coloured hair due to shampoo or rinse-off conditioner application cycles.
The method in question was developed because of the rising popularity of hair colourants and the demand for rinse-off products that would not affect the colour.
The washing process is the most significant factor in the removal of hair colour. Some colouring components are more easily washed out during shampooing or rinse-off conditioner application, and this ‘washing-out’ causes both fading and change of tone.
“In particular this is observed with red shades. Other sensory characteristics such as shine, body, lustrous feel and manageability are also linked to colour retention,” Unilever says in its patent application.
The method developed by Unilever sees a sample of the test formulation to be assessed applied to a model substrate in the form of a hair switch which has been artificially coloured.
The test formulation is then rinsed from the hair switch, and the rinse liquor is collected and analysed for the presence of removed colour
“The method provides improved sensitivity and differentiation, and enables the tester to compare different technologies in terms of effectiveness,” claims Unilever.
Specialized shampoos and conditioners have been designed specifically for hair treated with permanent colourants.
For example, certain families of silicones such as amodimethicone and derivatives have been described as a colour-lock aid in rinse-off hair care products.
A problem associated with hair colour protection technologies is that is difficult to evaluate their effectiveness.
Current methodologies for assessing the hair colour changes which are attributable to ‘washing-out’ tend to give hugely variable results.
“Often they are not sufficiently sensitive or differentiating, which makes it impossible for the tester to compare different technologies in terms of effectiveness. The present invention provides a solution to this problem,” adds Unilever.
WIPO Patent Application WO/2015/032724
Publication Date: 03/12/2015
Filing Date: 09/01/2014
‘Method of assessing hair colour changes’
Inventors: Unilever – Claire Louise Richards, Neil Scott Shaw