So I had an empty bag of sencha, and the thought struck me: "are these bags light proof?" I looked inside the bag, and held it up to a light (looking through the inside of the bag), and sure enough, they are not anywhere near completely light proof. I then did the same experiment with the bags my oolong come vacuum sealed in and the results were the same.
So my question is this: Is it ill advised to keep sealed tea in the original packaging out in the light?
(Some of those zip lock mylar bags do seem to be completely light proof. But the bags Japanese sencha and oolong often come in are not completely light proof)