Bristol is a city built on the rise and fall of the tides. Historically, the tides would make their presence felt, right in the heart of the city, lifting boats up to the quaysides at high water and stranding them in the mud below at low tide. From the beginning of the 19th century, however, with the creation of the Floating Harbour, the water level was kept constant and that connection was lost. ‘Tidelight’ symbolically re-established that dynamic connection between the city and the sea.

The interior of Bristol’s glass-fronted M Shed museum was filled with light that changed colour in direct response to the rise and fall of the tides. At night the whole building became a giant ‘lantern’ on the waterfront, responding to the sea beyond. 

To make Tidelight happen, continuous, real-time water level data from tide gauges out in the Bristol Channel was sent back to a computer inside the building. A piece of software converted this data, on-the-fly, in to a form that directly controlled the colour value of RGB lighting, already installed throughout the building as well as additional temporary lighting in the glass fronted foyer. 

Very low water was translated in to red light. As the water rose on the turn of the tide, the sensor data gradually caused the hue to transition through shades of orange, yellow, green and blue, all the way to violet at very high tide. The full tidal range out in the Bristol Channel corresponded to the full colour spectrum. 

As the tidal ranges vary over time, so more or less of the spectrum was reproduced accordingly. During a neap tide, the tidal range is low. The high tides are less high and the lows less low. 

On these occasions the coloured lights in M Shed may only ranged between orange and green. On a very high spring tide, though, the building was lit in a particularly intense violet, and during particularly low spring tides, the ‘lantern’ glowed a deep, blood red.