Context 170 - December 2021

32 C O N T E X T 1 7 0 : D E C E M B E R 2 0 2 1 polymer, with a surface course of rolled asphalt sprayed with a bitumen binder and dressed with around 3-millimetre stone chippings. Our intention was to make the surface look more industrial and honest, rather than the more parkland-monument aesthetic of the former light-tan-coloured, nut-brittle surface. The colour The bridge had been stripped down to bare metal and was to be repainted. This gave the opportunity to research the original colour. A seminar was held at the Ironbridge Museum at which experts discussed the evidence. It was not a straightforward decision, as of the at least 47 known images of the bridge made before 1845 all but four are grey-black engravings. The other four show the bridge as red-brown (WilliamWilliams’ 1780 oil painting of commis- sioned by Abraham Darby and painted before the bridge was finished), dark red (Robertson 1788), reddy-brown (Varley, around 1802) and pinkish (Westwood 1835). These images, it has been argued, could be illustrating low sunlight; they may have been coloured in later; and they may not have copied other images. The other main evidence considered was a specialist report by paint consultant Crick- Smith. This involved the microscopic analysis of paint samples from various parts of the bridge. Crick-Smith concluded that the earliest paint was a lead oil-paint, dark red-brown in colour, as depicted in William Williamson’s painting of 1780. This can be seen applied directly on to the cast-iron substrate, with multiple redecora- tions in a similar colour. With all the available evidence assessed, it was decided to paint the bridge red-brown. Lighting The existing lighting scheme needed to be replaced. It was decided that modern technology offered exciting new options for improved light- ing. LPA lighting was commissioned to design a scheme. Inspired by a quote in a newspaper 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’), it was decided to create a furnace effect so that visitors could imagine the bridge reflecting the fiery glow from the furnaces and forges in the gorge at the height of the industrial revolution. Constraints included the red-brown colour, which is less reflective than lighter colours; no equipment or cabling whatsoever being allowed on the bridge itself; the need to minimise light pollution; and not positioning the lights within a one-in-25-year flood risk zone. It was also impor- tant to minimise the impact within the setting of the bridge itself. The designers, Liz Peck and Bob Bohannon, computer-modelled the scheme so that beam angles and light strength could be carefully assessed. The resulting scheme can be remotely controlled by Telford and Wrekin Council for different events. The scheme produces a warm white light dur- ing the week and a dramatic view of the bridge at the weekend, when the lighting installation goes into furnace mode. This involves dynamic red and amber light overlaying the dimmed-back white light scheme, and generating movement by altering the intensity of the red and amber floodlights at the same time, to recreate the fiery skies of the 18th century. Bill Klemperer is principal inspector of ancient monuments at Historic England. The world’s first large cast-iron bridge spans the narrow Severn Gorge at Ironbridge. Microscopic analysis of paint samples from various parts of the bridge showed that the earliest paint was dark red-brown (Image: Crick-Smith Ltd)