Painted in 1983, Midi belongs to a group of works that were inspired by a trip to Egypt that Riley made in the winter of 1979–80. This excursion was to have a lasting effect on the artist, inspiring her work for over a decade. Paul Moorhouse explains, ‘During that trip she visited the Nile Valley and the museum at Cairo, and was able to study, at first hand, the tombs of the later Pharoahs in the Valley of the Kings. Riley was astonished by the art she found in these ancient burial sites carved out of rock and located deep in the earth. These sacred places were dedicated to the dead, yet the tomb decoration was a vivid evocation of life and light. Though their creators had used only a limited number of colours - red, blue, yellow, turquoise, green, black and white - the walls of the chambers receded behind images in which could be seen a bustling affirmation of everyday existence. In looking at the art and craft of Ancient Egypt in the Cairo Museum, Riley recognised that the same colours had been used in all aspects of the Egyptians’ material lives, from the decorative to the purely functional’ (see exhibition catalogue, Bridget Riley, London, Tate Britain, 2003, p. 22).
On her return to London, Riley found that these colours continued to exercise a fascination. Anxious to avoid appropriation, Riley chose to recreate the colours from memory, avoiding copying the hues from reproductions in books. This not only served to assuage her misgivings but imbued a personal resonance within the works, which explored her sensory reaction to the brilliance of tone she witnessed on her travels. As she began to explore this new, so-called ‘Egyptian palette’, it was clear that radical structural changes to her work would be required. Although limited in number, the diverse range of these intense colours needed a formal vehicle that was simpler than the curve she had been using for the last six years. For this reason she now returned to the more neutral stripe, which had occupied her work in the mid-1970s. This new structural reorganisation allowed for tones to be experienced individually, while simultaneously playing off those adjacent, to create a dynamic and visually arresting aesthetic and an increased generation of light. She also began to work in oil paint, rather than acrylic, which allowed for a greater saturation and density of colour.
The stripe paintings between 1980 and 1985 mark a pivotal moment in Riley’s career. Moorhouse explains, ‘They form a passage from the perceptual – optically mediated – character of her art before 1980, to her work from the early 1980s onwards which addresses pure sensation directly: visual experience as a direct response to its source’ (ibid., p. 22). This new perception is reiterated by Riley who commented, ‘Right up to, and in some ways including, the stripe paintings I used to build up to sensation, accumulating tension until it released a perceptual experience that flooded the whole as it were. Now I try to take sensation and build, with the relationships it demands, a plastic fabric that has no other raison d’être except to accommodate the sensation it solicits’ (see exhibition catalogue, Bridget Riley: Paintings and drawings 1961-2004, Sydney, Museum of Contemporary Art, 2005, p. 21).