James Newton

Commuters dashing through the pedestrian tunnel connecting London’s Kings Cross Station and Pancras Square now have cause to pause—or at least slow down—thanks to a new installation by lighting designers Speirs + Major. On view since March 6, “Halflife” is part light-source, part art-scape inspired by British physicist Ernest Rutherford’s duly named principal of decay. Taking the form of a gently curved light wall, the dynamic installation offers a white and RGB gradient that references the space’s transient nature.

“We wanted the rhythm of the piece to have a mathematical rigor and to create a sense of calm through repetition,” says Clementine Fletcher-Smith, an associate partner at Speirs + Major. “It feels like the space slows as the halving steps become smaller. As the sequence rebuilds, the light feels almost tangible as you become suddenly immersed in a newly illuminated space.”

"Halflife" comprises a single luminaire containing more than 350, five-pixel LED strips that measure 2.4 meters (7.9 feet) in length and are concealed behind semi-translucent glass diffusers to soften their glow and provide continuous light. The installation spans 98 meters (321 feet) horizontally and is 2.5 meters tall (8.2 feet); the tunnel's wall is 3.5 meters (11.5 feet) in height. Speirs + Major developed the lighting concept while The Light Lab, in London, designed and specified the installation using LED strips from NJO Technology, in Kendal, U.K.

Each LED strip utilizes RGB as well as white diodes set to 3000K and 6000K with a CRI of 80-plus, mixed to create a variety of colored hues, tones, and saturations. Over the course of the installation’s life, it will display 92,160 hues across the full color spectrum (shown below). Fletcher-Smith says that the mathematical sequence on which the design of the luminous gradient is based is also a nod to the UNESCO Year of Light in 2015. “[I]t shows how design, science, and technology can create something exciting and engaging,” she says.

The installation is permanent, but Speirs + Major anticipates that Halflife’s programming will last up to 20 weeks.

Speirs + Major

Among the biggest challenges, says Fletcher-Smith, is maintaining enough ambient light in the space so that pedestrians feel safe without overpowering the installation’s intended luminous effect. The project team achieved this by using other light sources—including LED downlights and LED linear uplights that backlight louvered grills on the wall opposite the installation—in the tunnel to maintain a low level of functional light. Another consideration was how to impress one-time visitors without boring commuters who traverse the tunnel daily. “The challenge was to make the piece interesting for a single journey, but for there to be a wider story that only the regular commuters would see,” she says.

James Newton

James Newton

Project: HALFLIFE, King’s Cross Tunnel, London
Client: King’s Cross Central Partnership, London
Lighting Designer: Speirs + Major, London and Edinburgh, Scotland
Project Team Members: Keith Bradshaw, Clementine Fletcher-Smith, and Iain Ruxton
Consultants: Control Lighting, Oxfordshire, U.K.  
Photographer: James Newton
Project/Installation Size: 90m tunnel
Manufacturers: The Light Lab and NJO Technology