Bridget Riley’s Cosmos is a large abstract artwork painted directly onto the gallery wall. Purchased in 2017 by the Christchurch Art Gallery Te Puna o Waiwhetū Foundation, it is the fourth of five significant works purchased to mark the Gallery’s time of closure following the 2010–11 Canterbury earthquakes.

Occupying an expansive white wall measuring five by nearly eight metres, Cosmos is 1.5 metres high, about the height of a tall bookshelf, and 4.6 metres wide. It begins at approximately adult thigh height from the floor. A total of 561 perfect discs, each the size of a generous cookie, have been meticulously painted in colours of pale mushroom, matt green and dull purple. Riley has toyed with these colours for years, inspired by the pointillist paintings of Georges Seurat. Spaced with absolute precision, the work consists of eight horizontal rows of 26 discs to form a stretched rectangle. The discs follow a shifting grid, like bricks laid in a wall, allowing for diagonal patterning reminiscent of trellis.

Born in South London in 1931, Bridget Riley was a founder of the op – short for optical – art movement. Works by op artists manipulate the eye to create an impression of movement – swelling, undulating, vibrating and even flashing – despite being static. They rely on the way our brains perceive visual information, creating effects that are not actually there, which can sometimes produce unsteadiness or disorientation in the viewer.

Riley’s work is careful and calculated, demanding active participation from the observer, even if it is not intentional. The colours are sequenced intuitively, without any pattern or rhythm in their placement. As she explains, they are “organised so that the eye can travel over the surface [as it] moves over nature. It should feel caressed and soothed, experience frictions and ruptures, glide and drift. Vision can be arrested, tripped up or pulled back, in order to float free again.” The careful spacing and geometric alignment of the discs create subtle, unexpected and sometimes fleeting effects unique to each viewer.

Since the late 1960s, Riley has employed professional painters or conservation professionals to execute her artworks. Cosmos was painted by a team of four people. The discs were carefully plotted and painted over several days. With up to four coats of paint used on each, and no visible brush marks, the discs are opaque, crisp and accurate. The Gallery purchased Riley’s ‘recipe’ for colour-matching and instructions for installing Cosmos, so it can be painted again in the future. The work cannot, however, be shown in more than two places at once.

The title Cosmos alludes to the work’s gravitational pull and sense of space and depth. It suggests an ordered, harmonious and systematic universe that could perhaps, in our challenging times, be a vision of calm and order.