The Iron Bridge as its name suggests was the first bridge in the World to be made of iron and is the icon for the start of the industrial revolution. During 2017-18, English Heritage, undertook a major £3.6m conservation project.
English Heritage’s clear instruction as the Bridge’s guardians was that nothing could be mounted on, under or through the Bridge, nor would be visually intrusive by day. Telford & Wrekin Council, the client, wanted a scheme which would extend the economic day of Ironbridge, would illuminate the downstream side previously left dark, was resilient to a possible 7m rise in river flood levels, but crucially, celebrated the history of the iconic Bridge.
The original concept was to deliver a white-light scheme for weekdays, a special effect on the weekend and the opportunity to have colour-changing for special occasions. The weekend effect was actually inspired by an unrelated, but co-incidental quote from Morgan Cowles, Head of Conservation & Heritage at English Heritage, in a Sunday Times article: *“Imagine the effect of the bridge lit at night by the fires from the furnaces and forges of Coalbrookdale, the structure glowing a demonic red”* – the weekend effect would thus become ‘furnace’.
This design could be achieved using unobtrusive columns with integrated RGB floodlight heads to deliver both schemes and enable Telford and Wrekin Council to colour-change on special occasions.
During the conservation project, English Heritage discovered patches of the original paint colour a red-brown, mahogany shade and painted the bridge back into this colour; thus mid-way through the lighting design, with budgets outlined and equipment sizes approved, the paint finish changed from a 25% reflective mid-grey tone receptive to most colours, to a 5% reflective red-brown. To maintain the required luminance would now require larger, more powerful projectors, stronger columns and more cost. Instantly the project grew into three years of careful negotiation and the overcoming of numerous challenges.
Among these were the geotechnical issues surrounding installing heavily-weighted columns into unstable gorge sides in a UNESCO world heritage site cut through by the River Severn. With the Bridge shrouded in scaffold and plastic sheeting for the conservation project, site trials were out the question, detailed computer models of the Bridge and gorge were made to determine quantities and aiming angles, to minimise glare and spill light through the filigree structure.
Wooden columns, with bespoke brackets to tightly bunch the projectors were designed to soften the daytime appearance, extended metal bases protected the wooden shaft from flood waters. These were then located in as unobtrusive places as possible. The louvred floodlights are mainly narrow beam, cross aimed horizontally to capture as much light as possible under the deck, or on the solid stone abutments to minimize glare and spill light.
The design delivers a static 3000K white-light scheme during the week. On Fridays and Saturdays, the innovative dynamic ‘furnace mode’ of red and amber overlaying dimmed back white light, creates the movement of the light from the burning skies of Coalbrookdale.
