Full-thickness bleaching of a PP bottle by calcium hypochlorite

I've had this bottle of calcium hypochlorite (Ca(OCl)₂) pool bleach in storage for maybe 4 years, I noticed it today and thought "huh that's weird, where'd I get this single white bottle from, it looks just like all my other ones except.." and you can probably guess the brainwave I had.

I checked the markings on the bottom and, sure enough, the white bottle was the exact same as all the orange ones.

Apparently, given enough time, the chlorine offgas from the decomposition of hypochlorite is able to penetrate polypropylene plastic and completely bleach whatever orange pigment they use in these prescription med bottles.

You can see that even the inking on the side label is faded and discolored, showing that the chlorine really does leak all the way through the plastic.

The exterior of the bottle is odorless, but I opened it and the contents still reek of chlorine, showing that the hypochlorite hasn't fully decomposed in the years since I stored it.

I'm curious how long it takes for the bleaching to become noticeable. Anyway, neat stuff.