In a career spanning five decades, Mark Rothko created a new form of abstract painting. “Untitled” (c1950-2) is one of his most celebrated paintings of the 1950s. Painted at the beginning of his mature period, it features his signature style of large rectangular blocks of colour arranged vertically one above the other, and is characterised by the use of bright, brilliant colours. The placing of one rectangle on top of another - and, in the case of “Untitled 1951-2”, separating them with a thin band of colour - is seen as a reference to the horizon and relates to the surrealist landscapes Rothko had painted in the early 1940s.

Largely self-taught, Rothko was friendly with artists such as Adolph Gottlieb and Milton Avery and was producing work heavily influenced by mythology and primitive art. He became involved with the abstract expressionists but his style was never gestural or frenzied in the way Jackson Pollock’s or Willem de Kooning’s was. He was more interested in creating forms that were soft and atmospheric. It was in 1949 that he arrived at his signature style of vertically arranged blocks of colour and he would not deviate from this format for the rest of his career.

Two large rectangles painted mainly in pink and yellow are separated by a strip of pink, while a smaller bluish-pink rectangle sits below them, adding a kind of weight to the painting. Using a mixture of oil paint and egg, Rothko has applied the paint in thin washes to give the colours a translucency that creates depth and space within the work. By applying the paint in such a way, the artist creates an effect whereby light seems to emerge from within the painting. The blocks of colour in this painting are more clearly separated from each other than they are in other works and the canvas overall is a lot smaller than many of the other paintings Rothko produced at this time.

If his work seems simple from a distance, up close the surface of the canvas reveals a range of different paint effects. The artist had a habit of turning a painting upside-down while he was working on it and subsequently the paint can sometimes appear to run up the surface.

As in many of his other works, in this painting Rothko has blurred the edges of the shapes so that they appear to float hazily against the background. These softly drifting rectangles of colour can engulf the viewer and suggest spirituality; indeed the artist described the experience of painting them as religious.

Studying the work of Rothko is an ideal way to introduce pupils to the importance and complexity of colour in visual art, as well as to the concept of abstract art. Encourage pupils to express their reactions to the work, although encouraging them to fantasise about what they can see in the painting (whether it be a set of clouds or some other kind of landscape) would be to rely on a cliched way of looking. Better to encourage an emotional response.

Rothko’s paintings are about emotion and the expression of feeling through the interaction of colour. The use of soft colour and strong horizontals as in this work is traditionally associated with calmness and tranquillity, so Rothko’s use of colour is often seen as alluding to beauty and harmony.

Rothko himself, however, was keen to dissociate himself from such interpretations, and, although he preferred not to offer much in the way of explanation, he did say there was a violence to his work that was as significant as any notions of serenity. This is clearly seen in his later paintings in which the strong bright colours are replaced by darker tones of red, brown and black.

Contrast “Untitled” with paintings that were part of a commission for the Four Seasons restaurant in New York. As he worked on the paintings he realised that the maroons, dark reds and blacks he was using would not be suitable for a restaurant setting. He withdrew from the commission and later donated the works to the Tate Gallery. They are hung in a sombre and austere room at Tate Modern, where reduced light invites solemn and meditative contemplation. The experience of seeing these murals under these conditions is not unlike visiting an impressive cathedral.

Indeed, Rothko’s most famous dark paintings are 14 virtually black paintings completed as a commission for a chapel in Houston. The Rothko Chapel, as it is known, completed a year after his death, is perhaps the ultimate expression of his unique vision and could be contrasted with the light and joyful Chapel of the Rosary in Vence, France, which Matisse, one of Rothko’s main influences, designed and decorated.

= James Sharp teaches at Elmhurst School in the London borough of Newham Noa-5 Mark Rothko 1903-1970 Rothko was born in Russia and emigrated to the US with the rest of his family in 1913. Despite acclaim, he suffered from depression throughout his life, and committed suicide in February 1970. To one interviewer, he said:

“I’m interested only in expressing basic human emotions - tragedy, ecstasy, doom. If you... are moved only by colour relationships, you miss the point.”