Liquid sky is a popular lighting

Lighting

Lighting or illumination is the deliberate application of light to achieve some practical or aesthetic effect. Lighting includes the use of both artificial light sources such as lamps and light fixtures, as well as natural illumination by capturing daylight...

 effect used by club

Nightclub

A nightclub is an entertainment venue which usually operates late into the night...

s and similar venues. It consists of a laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 scanning in a flat beam above the head of the crowd; as with most laser displays, for the effect to become apparent the air must be misted by a fog machine

Fog machine

A fog machine or smoke machine is a device which emits a dense vapour that appears similar to fog or smoke. This artificial fog is most commonly used in professional entertainment applications, but smaller, more affordable fog machines are becoming common for personal use. Fog machines can also be...

. The fog makes the beam of the laser visible, creating a luminous translucent ceiling of light. Air currents and the diffusion of fresh denser fog create a "swirly" or "marbled" effect.

Liquid sky has several advantages over other laser scanning patterns. The most notable one is that the effect can be visible for the entire crowd since you do not need to be "inside" as you would with a tunnel effect. It also avoids the controversial problem of crowd scanning, where the laser beam comes into direct contact with the crowd, possibly causing temporary blindness and sight loss.