This topic is really important to me and today I just found a great video on youtube about melting glass and soda flare and lampworking glasses and how they work to block out specific bands of light.
The guy has a spectrum analyzer with a computer display showing the way the glasses filter out the soda flare.
I think it well worth watching.
https://www.youtube.com/watch?v=Mwbd1qGvTeQ
This guy has a doctorate in physics I believe and although some of his other videos have some controversy due to his personality and his low tolerance for bullpuckey, his science is fact based and this video has none of the other stuff.