raden wrote:

White material especially after having been washed should fluoresce when
exposed to the light

It really needs to phosphoresce though (e.g. zinc sulphide), not
fluoresce (e.g. washing powders). Fluoresecence is immediate,
phosphorescence has a time delay.

If you could see something in the act of fluorescing you'd probably be
able to see the blue glow. Phosphorescence allows you to open it, close
it, put the power back on, open it up and then see afterwards if it had
illuminated.