It's not technically a salt in the strictest chemical sense, but it's often referred to as such. Zinc sulfide is a compound that emits light when exposed to radiation like ultraviolet (UV) light. This is the reason why luminous paint glows in the dark after being exposed to a light source.

Here's how it works:

* Excitation: When zinc sulfide absorbs energy from UV light, its electrons get excited to a higher energy level.

* Emission: As the excited electrons return to their ground state, they release the absorbed energy as light, making the paint glow.

While zinc sulfide is the primary component, luminous paints often contain other additives for better performance, like:

* Copper: To improve the brightness and duration of the glow.

* Manganese: To change the color of the emitted light.

* Binders: To hold the ingredients together and allow the paint to be applied.