Skin Mattifying, Oil Control and Sebum Efficacy Assessment

This test method relates to the evaluation of the ability of a skin care product to leave the skin matte and oil free, and to reduce the rate of sebum production on the facial skin.

The measurement of sebum is based on grease spot photometry. The mat tape of the instrument is brought into contact with skin or hair. It becomes transparent according to the sebum on the surface of the measurement area. The tape is then inserted into the aperture of the device and the transparency is measured by a photocell. The light transmission represents the sebum content.

The measurement of gloss is very important in the efficacy testing of skin care, hair care and decorative cosmetics (lipsticks, make-up, etc.). Skin and hair are supposed to show a natural, luminous gloss without appearing oily. Further, for nail cosmetics, gloss is an important parameter.

The measurement of gloss is based upon reflection. Parallel white light is created by LEDs in the probe head. To be able to emit light at 60° in a relatively small and uniquely designed measurement head, light is sent out at 0° and reflected by mirrors to 60°. Two separate measurement channels measure the direct reflected light (also guided by a mirror at the same angle into the reflection channel) and the diffuse reflected (scattered) light. The scattered/diffuse reflected light is measured at 0° (completely vertically above the measured surface) under the assumption that light is scattered in the same way over all degrees (diffuse channel). Therefore, the instrument expresses both, the portion of directly reflected light (gloss) as well as the diffuse scattered portion from the skin surface.

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