Bubble light

It is generally sealed in a glass vial or capsule to prevent its release; if it is broken, the area should be evacuated until the fumes have dissipated.

Some early bubble lights instead used a lightweight oil or camphor (a white substance used in some moth balls) to create the low boiling point.

Bubble lights of all kinds operate best when the top of the tube is significantly cooler than the bottom, thus increasing the temperature gradient.

The clear light bulb is enclosed in a plastic base made up of a "bowl" and a "cap", usually of different colors.

Bases are now often made to look like figures such as Santa Clauses or snowmen, or decorative objects and symbols, rather than the plain ribbed plastic.

Other bubbling lights are much larger and sit on a table or floor, occasionally with fake fish which "swim" up and down as they change buoyancy.