Sun assessment
SP Equation's sun evaluation division supports brands in scientifically validating the effectiveness of their sunscreen products. Using rigorous in vitro methods, we evaluate UVA and UVB protection according to current regulatory requirements (ISO 23675:2024, ISO 24443:2021, FDA, Boots Star Rating System).
We also offer screenings, formula comparisons, photostability and water resistance analyses.
Our goal: to guarantee our clients reliable, reproducible, and usable results for regulatory submissions or marketing purposes.
Methods
IN VITRO SUN PROTECTION FACTOR - ISO23675:2024 STANDARD
The principle consists of measuring UV transmission (from 290 to 400 nm) through a thin layer of a sunscreen applied to the rough side of PMMA sheets, before and after exposure, under standardized application and measurement conditions.
The mathematical formula for in vitro SPF is described in ISO23675:2024.
The procedure complies with the application, measurement, and calculation guidelines.
IN VITRO UVA PROTECTION FACTOR CRITICAL WAVELENGTH - ISO24443:2021 STANDARD
The principle consists of measuring UV transmission through a thin film of a cosmetic product applied to the rough side of PMMA sheets, before and after exposure to a specific dose of UV, in order to take photostability into account. The UV spectrum measured before exposure is adjusted in amplitude to correspond to the SPF measured in vivo or in vitro. Similarly, after exposure, the same adjustment coefficient is used to obtain an in vitro UVA-PF factor correlated with the in vivo UVA-PF factor. The procedure complies with the guidelines of ISO24443:2021.
CRITICAL WAVELENGTH ACCORDING TO THE FDA2011 FINAL RULE - 21 CFR 201.327
This method demonstrates that a sunscreen product offers broad-spectrum protection, i.e., against both UVB and UVA rays, according to the criteria defined by the FDA.
The analysis is based on measuring UV transmission through a layer of product applied to sandblasted or molded PMMA sheets after exposure.
UVA/UVB ABSORBENCE RATIOS ACCORDING TO THE BOOTS IN VITRO METHOD (2008) AND "BOOTS STARS" RATING
The Boots method assesses the level of UVA protection versus UVB protection of a sunscreen product according to UK requirements. It assigns a number of stars (from 1 to 5) based on the UVA/UVB ratio, allowing the balance of protection to be assessed.
EQUIVALENCE OF 2 FORMULAS / COMPARISON OR STABILITY
This method aims to compare the photoprotective profile of two sunscreen products: a test formula and a reference formula (old formula, market product, or stabilized formula).
After application to sandblasted or molded PMMA sheets, a series of 5 UV transmission measurements between 290 and 400 nm are taken on each sheet, and a statistical comparison is conducted.
