Solar Eclipse Glasses Degradation

Solar eclipses provide a unique opportunity for both professional and amateur astronomers;however, direct observation of the Sun without proper eye protection poses serious risksof retinal damage, including eclipse blindness and photo-thermal injury. This study examinesthe effectiveness and potential degradation of solar eclipse glasses over time.A total of 13 solar eclipse glasses of varying ages were analyzed under identical observationalconditions to assess their spectral transmission properties. The evaluationfocused on the visible and infrared ranges, while acknowledging instrumental limitationsin the ultraviolet (UV) spectrum and part of the visible spectrum. The study also considersthe compliance of these glasses with international safety standards, particularly ISO12312-2:2015.The results reveal variations in light attenuation among one sample, with some olderglasses exhibiting higher transmission levels than recommended, many other old sampleswere as safe as new glasses, but currently impossible to trace which glasses would besafe and which not. This raises concerns about the long-term reliability of eclipse glassesand their potential degradation due to environmental exposure and material aging. Inaddition, a comparative evaluation was conducted to analyze qualitative factors such asvisual comfort, reflection reduction, and optical clarity.These findings emphasize the importance of verifying the safety and compliance ofeclipse glasses, especially when reused over extended periods. Although that can be truefor glass nº 10(not safe), in contrast glass nº 8(safe), still today as protective 20 yearslater as most of the new glasses. The study contributes valuable information about thepotential obsolescence of these protective filters and highlights the necessity of periodictesting to ensure their effectiveness in safeguarding vision during solar eclipses.