Like most things that have a glowing pigment in them, you will have to get some light on them.
Because of some issues with UV, we wouldn’t recommend leaving these guys out on a windowsill for too long but if you have a high lumen light/torch this is a great way to get your glow on!
Simply hold your toy to/under the light for a couple of minutes and this should set it a-glowing, these will dim over time but just hit it with the touch again and it’ll recoup its brightness. If you happen to have a black light this makes them glow even brighter much quicker.
Pics: Our Glow in the Dark Blue Can both before and after