From 1968 to 1969 Bell commissioned the building of a coating device in order to produce work on a more environmental scale. During the plating process, thin metal films are deposited onto another material, mainly glass, resulting in a coating that allows light to be reflected, transmitted and absorbed simultaneously. He began creating sculptural installations with large sheets of glass that were rendered partly mirrored and partly transparent through the vacuum deposition procedure, thereby making the glass surfaces almost disappear and volumes become weightless. The colours which become visible are known as ‘interference colour’; an illusion which results when light hits the sculptures’ surface. Throughout this period, Bell produced interior wall environments, such as The Black Room for both the Museum of Modern Art, New York (1969) and the Tate Gallery (1970).
In 1978 Bell began experimenting with depositing the coatings on paper, finding in the process that the paper did not transmit light but only reflected or absorbed it. This body of work, known as ‘Vapor Drawings’, continues to this day. In the early 1980s Bell began combining different surface qualities as layers within the ‘Vapor Drawing’ oeuvre, such as Mylar and laminating film, to create the so-called ‘Mirage works’ – a mirage being an illusion which results from a combination of heat and light.