VonBingen
I don't think the glass has to be a dark color. I, too, put it in a closed cabinet, mostly so the smell doesn't offend my partner.
Some Indian practitioners recommend putting it in the sun to encourage evaporation for a more concentrated brew.
I, too, had a tightly bottled jar that was several weeks old, and I swished with it, as I am used to do with aged urine. OHG! It burned! There was a lot of ammonia in that jar.
I'm sure there's some small amount of ammonia still bound into several days old urine, but not anywhere near that amount.
From what I understood, reading here and there, the older, and the more evaporated, the more concentrated the minerals in the urine.