As I said, I had the dial directly in front of the LED for about 5 days straight. Every now and then a short break when I didn't realize that the battery was empty. I didn't have the 18650 batteries in it, but a number larger (I think 21700 - but I'm not quite sure of the name) - they last a bit longer....
The process is relatively slow. I saw virtually no effect for the first two days, but from a certain point onwards it went much faster, as if the reaction needed a starting point. The effect then extended from a point around the 7 o'clock marker.
Be interesting to see what it would do to a black Raffles and hand set.