Minimalism and Conceptual Art were primary movements in the 1960s and 1970s. Artists reduced art to its bare essentials, producing works that are remarkable for their apparent lack of content. Many painters created works using line and broad areas of colour, while sculptors began to focus on the nature of their materials. They aimed for a viewing experience unaffected by anything but the work of art itself.

Minimalism describes radical developments within the New York art scene of the 1960s, and is identified with the work of sculptors Donald Judd, Robert Morris and Sol LeWitt, and painters such as Jo Baer and Robert Ryman. It is characterised by an aesthetic of austerity. Sculptures consist of reductive or primary forms in modular and serial arrangements, fabricated using industrial materials and methods. Paintings are simple, geometric, often monochromatic. Artists such as Bridget Riley and Frank Stella represent a parallel current in art: their experiments with periodic structures, colour combinations and surface modulation show a similar concern to make work within particular strictures or with an economy of means.

Source: National Gallery of Australia

Many Minimalist artists reacted against the emotive Abstract Expressionist movement and sought to create an art devoid of emotional gestures. They wished to strip art to its barest and most simplified elements.

These artists questioned the need for a subject in art. The materials became the subject. Emotion was unimportant. They wished to remove the artist's unique mark, preferring impersonal mass-produced materials available commercially. Artists Dan Flavin and Donald Judd challenged traditional sculpture by defying the need for frame or pedestal, placing their art directly on the floor or between walls.

One Minimalist artist, Ad Reinhardt defined the style in the following terms:

"The more stuff in it, the busier the work of art, the worse it is. More is less. Less is more. The eye is a menace to clear sight. The laying bare of oneself is obscene. Art begins with getting rid of nature."
http://en.wikipedia.org/wiki/Minimalism

Conceptual artists developed this idea a step further. They wished to explore art at its most fundamental. For Conceptual artists the important thing was the idea behind an artwork, and not the object that was produced.

"In conceptual art the idea or concept is the most important aspect of the work. When an artist uses a conceptual form of art, it means that all of the planning and decisions are made beforehand and the execution is a perfunctory affair. The idea becomes a machine that makes the art."
Sol LeWitt
Quoted in Paragraphs on Conceptual Art by Sol LeWitt, Artforum, June 1967.

Source: NGV

During the 1960s a number of artists began to make distinctive and original work which appeared to share an aesthetic sensibility remarkable for its austerity and restraint.

Advocating total abstraction, the artists associated with minimalism believed that a work of art should be an independent object in the world. Rather than imitating, symbolising or embodying something else, it should be defined by its evident physical characteristics: materials, form and scale, and structural principles. The real-time experience of the viewer, physically present in the space occupied by the work, was also central to its meaning. While each of the artists included here had their own distinctive approach (and developed a much wider practice), the works in this room may be characterised by the spare rigour of their forms, an emphasis on geometry and mathematics, and essential qualities such as weight and surface.

Minimal artists consciously distanced themselves from an earlier generation of post-war painters and sculptors, whose highly expressive approach emphasised the presence of the artist in the making of the work. Instead they favoured impersonal industrial materials and processes of fabrication based on concepts of mass production. Although principally associated with work in three dimensions, related concerns were explored in paintings such as the all-over grids of Agnes Martin or Jo Baer’s experiments with the optical effects of colour.

In its desire for an autonomous art, minimalism has its roots in early twentieth-century experiments in abstraction, particularly Russian constructivism. Crucially important to the development of conceptual and process art and contributing to the evolution of installation practices, minimalism occupies a pivotal position in the complex reorientation of art from modernism to post-modernism.

Source: Tate Modern