Radium stickers do not actually contain radium. The term "radium" is often used colloquially to refer to materials that exhibit a glowing or luminescent effect. These stickers or materials are typically made using a substance called phosphorescent or fluorescent pigment.
Phosphorescent materials absorb and store energy from various light sources, such as natural or artificial light. When the lights are turned off or when the sticker is placed in a dark environment, the stored energy is slowly released in the form of visible light, creating a glowing or luminescent effect. This phenomenon is known as phosphorescence.
The pigments used in radium stickers are often composed of materials like zinc sulfide or strontium aluminate, which have the ability to absorb and emit light. These pigments are mixed with a binder or adhesive and applied to stickers or other objects.
When exposed to light, the phosphorescent pigment in the stickers absorbs energy. Then, in the absence of light, the stored energy is gradually released over time, causing the sticker to emit a glowing or shimmering effect. This effect can last for a certain duration, depending on the specific properties of the phosphorescent material used.
It's important to note that while the glow of radium stickers may resemble the luminescence associated with radioactive radium, the stickers themselves are not radioactive and do not pose any radiation hazard.