Solar Eclipse Glasses Degradation II

This report presents the results of a systematic study on the potential long-term degradation of solar eclipse glasses. A total of 70 models, manufactured between 1999 and 2025, were analyzed at the Advanced Scientific Instrumentation Laboratory (LICA) of the Complutense University of Madrid. The findings show that while many glasses retain their protective properties even after more than two decades, some manufacturers exhibit clear signs of optical or transmission degradation. This raises concerns for users reusing old eclipse glasses, as there is no simple way to determine which models remain safe. The study recommends purchasing only glasses with CE marking, full compliance with ISO 12312-2:2015, and approval by a notified body, and discourages the use of glasses older than 15 years or those lacking manufacturer information, which may indicate counterfeit products. Importantly, glasses purchased and manufactured in 2025 are expected to remain safe for the upcoming eclipses of 2026, 2027, and 2028, provided they are certified and free from visible defects. This work provides a crucial reference for manufacturers, regulators, educators, and the general public in preparing for the major eclipses visible in Europe in the coming years. It emphasizes the importance of traceability, standardization, and public education to ensure safe solar observations