An American painter renowned for his luminous, spiritually compelling abstract blocks of colour: the style known as colour-field painting. Many of his greatest works use various shades of red deepening into crimson, maroon, and black: notably the monumental series of the Seagram Murals, now in a room of their own in the Tate Modern in London. Another important series is the Rothko Chapel in Houston.

In most of his works a single background colour is largely covered by two, sometimes one or three, large blurred rectangles, reaching horizontally almost to the edges. The colours are often though not always neighbours: blue and green; or red and yellow and white. They gain much of their effect from variation in intensity: a bright scarlet next to a muted scarlet, and a looming expanse of black above them.

Some works are vertical, in that the inner rectangles reach almost the upper and lower edges rather than the sides. In later works he introduced pierced regions, so that the effect is of some great lintelled standing stones or a doorway into the beyond.

His colours are never precise; never single-shaded or clean-edged. The boundaries waver; some appear to fade into their background; and repeated applications of paint across them gives them a complex internal texture. The effect is of natural places: the sea at night, perhaps, all features drained out of visibility, leaving an infinitely far sky hazed with cloud, an ever-changing layer of ocean, a shimmering horizon joining two vast regions.

He intended them to be deeply spiritual appearances, and they are, in an extraordinary way. The vivid colours and muted shades seem to resonate in the brain, like a mandala, like a sun blazing through the Parthenon or Stonehenge, or like a stargate beckoning you to step forward and through to some unknown and unimaginable paradise.

People sit in the Rothko room at the Tate for a long time, in meditation, in refreshment. I leave the gallery after that; I can't look at any other paintings. I feel cleansed the whole day.

Marcus Rothkovich was born in Dvinsk in Russia in 1903, in what is now Latvia; the family were Jewish, and migrated to America in 1913. Studying at New York and Yale, in 1935 he co-founded an Expressionist group called The Ten. His work at this stage was similar to that of some contemporary European artists, and he became influenced by Joan Miró. Gradually his figures became more amorphous, and from about 1947 he was doing pure colour-field painting, the contribution he and Barnett Newman (an artist who does nothing for me) made to the wider school of abstract expressionism. His colours became sombre in later life. He committed suicide in 1970.

The progression of a painter's work ... will be toward clarity; toward the elimination of all obstacles between the painter and the idea, and between the idea and the observer. ... To achieve this clarity is, inevitably, to be understood.