Iron Bridge, UK
The Iron Bridge crosses the River Severn in Shropshire and is located within the Ironbridge Gorge near the town of Telford. Opened in 1781, it was the first bridge in the world to be constructed from iron and is over 100ft in length.
Designed by Thomas Farnolls Pritchard and Abraham Darby III, the bridge’s purpose was to link the neighbouring towns of Broseley (known for industry), Madelely (a smaller mining town) and the village of Coalbrookdale (significant for its iron ore smelting). The river beneath it was crucial for transporting resources between the mining towns that lie along the gorge. All of these factors combined mean the Iron Bridge and the surrounding gorge are icons for the start of the industrial revolution and today form a UNESCO World Heritage Site.
While floodlights have been lighting the bridge since the late 1970s, at 40 years old, they were no longer fit for purpose, illuminating only one side of the bridge and regularly being flooded by the river below. After English Heritage completed a £3.6m conservation project in 2017-18 to repair the bridge’s cracked joints, Telford & Wrekin Council decided that a new lighting scheme would celebrate this restoration and the 50th anniversary of Telford new town. That’s where LPA Lighting Designers come in.
The new lighting project seemed relatively straightforward to begin with. The clients wanted a scheme that would extend the economic days of Ironbridge and Telford and illuminate the bridge from either side, while English Heritage asked that neither luminaires nor cables would be mounted on or under the bridge and the visual impact of the fittings during daylight hours be minimal.
Based on these objectives, LPA’s Liz Peck and Bob Bohannon proposed a scheme using RGB floodlights mounted on columns. White light would be used during the week with special effects and color change at weekends and for special occasions.
All of these plans changed, however, when English Heritage discovered that the mid-grey bridge was originally a red-brown color. The whole bridge was then repainted in a mahogany shade – and as a result – the lighting scheme had be re-imagined. What was a 25% reflective mid-grey color became a 5% reflective brown. To maintain the required luminance with a much lower reflectance, luminaires with greater lumen packages would need to be used. These would require bigger fittings at a higher cost, so what was a simple project then became much more complicated.
Unable to access the real bridge for mock-ups (it was still covered in scaffolding and plastic sheeting for the restoration project), the designers used metal sheets and paint to determine the best color temperatures with RGB no longer an option and to make sure they could still create a ‘furnace’ effect (to represent the flickering fire from the furnaces and forges from nearby Coalbrookdale). The team also created detailed computer models of the bridge and sourced a laser-cut model of it which meant they could demonstrate beam angles and spill light to the various stakeholders including Telford & Wrekin Council, English Heritage, Enterprise Telford, Historic England and the UNESCO World Heritage Site Steering Group.