How to make it luminous.
( the black backgound means can luminous at night )
1.This backpack needs to absorb light throughout the daytime and shine at darkish.
2.The longer the backpack absorbs light,The longer the backpack at nighttime glow time.
3.You need to carry it throughout the photo voltaic for some time.And then stroll to the darkish place.
4.Then will in all probability be luminous.