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 risks
of retinal damage, including eclipse blindness and photo-thermal injury. This study examines
the effectiveness and potential degradation of solar eclipse glasses over time.
A total of 13 solar eclipse glasses of varying ages were analyzed under identical observational
conditions to assess their spectral transmission properties. The evaluation
focused on the visible and infrared ranges, while acknowledging instrumental limitations
in the ultraviolet (UV) spectrum and part of the visible spectrum. The study also considers
the compliance of these glasses with international safety standards, particularly ISO
12312-2:2015.
The results reveal variations in light attenuation among one sample, with some older
glasses exhibiting higher transmission levels than recommended, many other old samples
were as safe as new glasses, but currently impossible to trace which glasses would be
safe and which not. This raises concerns about the long-term reliability of eclipse glasses
and their potential degradation due to environmental exposure and material aging. In
addition, a comparative evaluation was conducted to analyze qualitative factors such as
visual comfort, reflection reduction, and optical clarity.
These findings emphasize the importance of verifying the safety and compliance of
eclipse glasses, especially when reused over extended periods. Although that can be true
for glass nº 10(not safe), in contrast glass nº 8(safe), still today as protective 20 years
later as most of the new glasses. The study contributes valuable information about the
potential obsolescence of these protective filters and highlights the necessity of periodic
testing to ensure their effectiveness in safeguarding vision during solar eclipses.