Some like it dark and I'm one of them.
I bought a pair of sort of cool looking trifocal transition lenses sun glasses last summer, with the idea of having to only deal with one pair of glasses that I need for both close and far while touring. After riding a few times, I was disappointed, to say the least when I discovered that behind a helmet shield, or for that matter inside a car, they would not turn completely dark. Since I mostly ride with the face shield up in order to inject the smells and surroundings into my helmet, it wasn’t a big deal.

But then today's ride happened, and what a surprise! Any chemists in the crowd?

Minnesota temp today is in the teens today, and I just got back from a great 80+ mile ride on the hidden twisties along the Mississippi. I went down to see the bald eagles that start to line the shores each year in wait for the fish near Redwing and Wabasha, MN.

The lenses are dark! The cold temperature apparently for some reason, results in the glasses getting pitch dark inside the shield, where in nice termps, they get sort of pissy gray.

Any ideas of why this occurs?