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Aug 25, 2014
In any sun protection evaluation method, an irradiation step is required to determine the photostability of the UV filters in a product. The aim of this study was to identify key parameters involved to improve this UV exposure. Here, the authors consider temperature at the substrate surface, air flow influence and beam uniformity during UV exposition.
Mar 20, 2014
SPF test results from substrates treated using a traditional sandblasting technique are compared with those from substrates treated using a new process. Based on the topographic control of 10 batches and 34 sunscreen evaluations, the authors concluded the new process had better topographic reproducibility, consequently improving the SPF repeatability and reproducibility in vitro.
Nov 1, 2013
This work evaluates the impact of applied pressure during sample spreading on the in vitro measurement of UV transmission. The authors work in a range of pressures between 50–200 g and demonstrate that pressure control is a key parameter that should be strictly controlled to ensure the reliability of test results.
Oct 1, 2013
Repeatability and reproducibility are crucial to validate any test method. In order to master these criteria, the authors developed an automated spreading device and compared it with human spreading. Application of the device in eight laboratories and using 36 sunscreens revealed great improvements via automated spreading, ensuring good intra- and inter-laboratory variability.
Sep 1, 2013
This work evaluates the impact of three different substrates on in vitro SPF measurements, and defines experimental conditions to improve their correlation with in vivo values. Evaluations of 32 products, shown here, led the authors to conclude that molded substrates improved repeatability and correlation with in vivo SPF values.
Sep 1, 2013
If like me, you’re just daydreaming of the beach, this collection of articles will enlighten you with its focus on sun protection, SPF testing, damage repair and more.
Jul 1, 2013
This work evaluates the impact of temperature on test substrate surfaces during the application, spreading and drying steps of the in vitro method to measure ultraviolet (UV) transmission. The authors work in a range of temperatures, between 20°C to 35°C, and demonstrate that controlling temperature is a key parameter and should be strictly controlled to ensure reliability.
Mar 1, 2013
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.
Mar 1, 2011
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.
Mar 1, 2011
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.
Sep 1, 2009
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.