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This work evaluates the impact of a plasma treatment on test substrates to modify their surface energy, to more closely correlate in vitro SPF measurements with in vivo measurements—without chemically altering the test products. The authors chose the level of plasma modification to use on a substrate based on in vivo values; they explain how to choose it regarding specific formulas in a further paper.
Cosmetics & Toiletries is pleased to welcome Marc Pissavini, PhD, to its prestigious Scientific Advisory Board. Pissavini began his career as an analytical chemist and in 1998, joined the sun research department of Coty-Lancaster in Monaco. Since 2008, he has served as the director of Basic and Applied Research for the company.
After 25 years in the industry, Gavin Greenoak, managing and scientific director of the Australian Photobiology Testing Facility Pty., Ltd. (APTF), continues to strive for a better understanding of the interaction of light and the human body. Greenoak’s career began in cancer research, which has afforded him unique insight of skin biology and the effects of sun exposure.
The present article describes a reproducible method for determining the photostability of sunscreen products. This method is based in part on the in vitro determination of the UVA protection factor as proposed by Colipa for the irradiation aspect, and on the spectroscopy of a sunscreen in dilute solution for the absorbance measurement aspect.
“Science Exposed” is a new column aimed at digging into industry controversies to strip them down to the scientific facts. Here, sun protection expert Brian Diffey, PhD DSc, critiques the current SPF test method.
In order to prepare the industry for the upcoming Sunscreen Symposium, organized by the Florida chapter of the Society of Cosmetic Chemists, industry expert Tony O’Lenick asks Dennis Lott to explain the difference between SPF and calculated SPF. This is the first of two columns on sun protection.
Methods for determining SPF in vivo are based on a biological response by human skin. To overcome intrinsic variation in these methods, large numbers of volunteers and statistics are required; however, these concepts are often poorly understood or worse, misinterpreted. This article discusses how these values should be interpreted and explains what they mean to formulators.
A sunscreen layer’s thickness is critical to its SPF. However, current regulations specify a mass application rate for testing, rather than a volumetric application rate. This significantly underrates the SPF values of mineral sunscreens due to their higher densities since, compared with their relative organic counterparts, thinner films are being tested, as will be shown here.
Here, the authors describe a variable that affects the results of SPF testing in vitro—the roughness parameter—and investigate this variable using standard and molded poly(methyl methacrylate) (PMMA) substrates. They conclude that use of a molded substrate, along with the described control chart, improves the reproducibility of in vitro SPF test results.
Cutest Systems Ltd has installed a Labsphere UV-2000S sunscreen analyzer at the companies laboratories in Cardiff, Wales.