Alma Thomas' paintings instruct us in color and pattern. Her celestial fantasies, dabbed onto canvas in short thick strokes, form geometric designs. Her aerial views of hydrangea gardens are concerned with the juxtaposition and exuberance of colors. Thomas, who began painting at age 60 after years teaching in the D.C. public schools, gained a national reputation as an abstract painter. Her career was capped with a one-woman show at the Whitney in 1972, six years before her death at 87. A 47- painting exhibit now at the Museum of American Art is a dizzying tribute. The show traces Thomas' progression from watercolor studies to acrylics, from earthy works to space-age subjects. From her series based on the "Snoopy" lunar module's vantage point,"Snoopy -- Early Sun Display on Earth" depicts a flash of yellow breaking through a circular pattern of blues like the sun rising on the world. Light grows more radiant at the edges, dissolving into orange and yellow. The color arrangement is vibrant, the lines seem to move. Thomas was influenced by her friends in the Washington Color school -- Gene Davis stripes and Kenneth Noland targets are similarly concerned with color and geometric form. But she remained apart: Thomas never used masking tape to mark her stripes, she avoided their stain methods and fascination with technique. In fact, the power of her painting lies in the rugged, uneven brushwork, never obscuring the manual effort that went into the creation.

A LIFE IN ART: ALMA THOMAS, 1891--1978 -- At the Museum of American Art through February 22.