That was my experience too. I tried the Rustoleum one on a rock and a stepping stone. It was so faint as to be worthless and I did multiple coats too.
There is glow in the dark ceramic tile. I used it on my husbands Astronomical Observatory sign. I made a Kokopelli and a comet in the glow tile. It works very well, and stays bright most of the night. It has been up a few years now and is still going strong. This tile would be wonderful to use in a bathroom. You'd never need to turn on a light!
