According to an online survey performed in 2006 by the personal care giant, over 50 percent of respondents said they had experienced problems with foundations that gave too pasty or ashy a color.
Different spectral curves
Although a foundation can nominally be designed to match the skin color, the way it transmits and reflects light will differ.
A material’s reflection (or transmission) of light at different wavelengths can be plotted in graph form and is referred to as a spectral curve. And when the skin’s spectral curve is different from that of the foundation, undesirable effects may occur, explained the scientists.
When a foundation provides too much reflection in the 400-470nm wavelength range (the blue end of the spectrum) it can often look pale and pasty.
Similarly, if the foundation provides too little reflection in the blue to green wavelengths (400-550nm) it may appear too orange and dark.
Improving the model for predictions
One of the ways manufacturers can make formulations match target colours is to use the Kubelka Munk model which relates reflection and transmission to the absorption and scattering coefficients of materials.
However, P&G claims to have improved the Kubelka Munk model making what was originally designed for paint manufacturers more applicable to the skin.
As the skin is several millimetres thick light at the lower end of the spectrum will not penetrate as deeply as other wavelengths. Factoring this into the model improves the accuracy of the predicted spectral curves, explained the company’s researchers.
The scientists, who presented their findings at the recent AAAS (American Association for the Advancement of Science) annual meeting, say that these advances in understanding have allowed them to identify a new material to use in foundations which will provide coverage whilst better matching the skin’s spectral curve.
The Cincinnati-based company claims this will ultimately lead to new foundations that will not have the pasty or ashy effect identified by consumers.