Square Forms (two sequences) is one of the cast bronze sculptures that characterize Hepworth's late oeuvre. The sculptor started producing works in bronze in the late 1950s and quickly discovered that the elasticity and strength of this medium considerably broadened both the range and scale of her work. Taking inspiration from her longtime friend Henry Moore, Hepworth also adopted bronze as a means to facilitate the dispersal of her work around the world. The present work demonstrates Hepworth's masterful ability to achieve equilibrium between the demands of this new material and its expressive possibilities. Commenting on her recent production in 1962, the artist stated: "Certain forms, I find, re-occur during one's lifetime and I have found some considerable pleasure in reinterpreting forms originally carved, and which in bronze, by greater attenuation, can give a new aspect to certain themes" (quoted in Barbara Hepworth, exh. cat., IVAM, Valencia, 2004, p. 137). The poet and art critic Herbert Read, initially skeptical of Hepworth's use of this new material, remarked: "I have now come to realize that what I previously discerned as the artist's fundamental purpose, 'to infuse the formal perfection of geometry with the vital grace of nature' is as fully realized in bronze as in carved wood or stone" (quoted in ibid., p. 67).
Although cast in 1966, the present sculpture was first conceived in 1963, shortly after the unveiling of Hepworth's monumental Single Form outside the United Nations Secretariat in New York. The sculptor made all of her bronzes by constructing an aluminum mesh armature and covering it in plaster with a spatula, but whereas the sculptor carved out the surface of Single Form using axes and other tools, she constructed the present sculpture out of eight individual square units and left the smears of plaster largely unaltered. Her evident exploration of surface within this open and linear composition underscores her preference for natural light. The rugged topography of the squares, which includes a recessed half sphere, catches the movement of the sun; the changing light and shadow lend vitality to the forms through the interplay of void and volume. The green and gray patina both underscores this textural vivacity and reflects Hepworth's experimentation with and appreciation for the finishing work that is the crowning process in bronze casting.
The geometric structure of the present work, which is a marked departure from Hepworth's customary organic curves, recalls Constantin Brancusi's stacked primitive forms in his totemic wooden pedestals and works such as Endless Column (1938; Târgu Jiu, Romania). Like Brancusi, Hepworth also created bronze versions of her carved sculptures. However, the two "sequences" of squares may also reference the double-helix molecular model of DNA, in which two chains of polynucleotides coil around the same axis. Indeed, James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize for discovering the double helix in 1962, just before Hepworth began work on Square Forms. Nature's diversity was an inexhaustible source of inspiration for the sculptor, as she noted: "In the contemplation of nature we are perpetually renewed, our sense of mystery and our imagination is kept alive, [...] it gives us the power to project into a plastic medium some universal or abstract vision of beauty" (quoted in ibid., p. 131).