When small is big

Although the word ''miniature'' is said to have derived from the vermilion pigment, minium, beloved of medieval manuscript illuminators, we associate it with the small, the minimal. Very small graphic depictions have probably always coexisted with life-size and larger-than-life art forms and always will. There are ancient portrait coins and modern postage stamps.

In the history of Western art, portraits of all sizes flourished as art became secularized after the Renaissance. In the 19th century, when photography entered the scene, the decline of painted portraits was signaled. The work of two women marks the beginning and the end of the golden age of miniature portraiture.

It was Rosalba Carriera who introduced the use of thin wafers of ivory painted with transparent water colors. She traveled from her native Italy to Paris to become a court painter to King Louis XV. Her fame spread rapidly throughout Europe. Her work is described as being pictorially vivid and full of animation.

These same phrases might be used for the work of Eda Nemoede Casterton, a Midwestern American artist. Her tiny pictures - and the one here reproduced is actually only 2.75 inches by 3.75 inches - make no concessions to their size. Each is a well-realized, strongly modeled, carefully detailed portrait. They were praised for their poetic evocation of mood as well as fidelity to physical likeness. The skin tones are clear and delicate.

Casterton delighted in painting children. When her career was just burgeoning , she remarked, ''I want to paint children in the sunshine, young girls out of doors with the wind in their hair and the sky's deep blue in their eyes.'' Young Mae Olson, painted in her pale, frothy turn-of-the-century finery, looks ready to spring out of her wicker rocking chair and exchange her richly detailed background for the sun and the wind.

When Eda Nemoede was about the same age as this subject, she drew copies of the pictures on her schoolroom walls when she should have been paying attention to more conventional studies. Rebuked for her ''naughty behavior,'' she nonetheless persisted. Her sturdy German immigrant family considered her drawing an idle pastime and influenced her to study shorthand and become a stenographer.

Eda took this as an opportunity to pay for private half-hour lessons on her lunch hour with a leading miniaturist and teacher at the Chicago Academy of Fine Arts. She later declared the appeal of miniatures for her was that they were ''small paintings painted in a big way.'' Their size permitted her to carry them to her employment. She arrived an hour early and stayed an hour late to work on them. Her teacher regarded her pupil so highly that, when she herself was unable to continue, she turned over to her unfinished commissions and her classes at the academy. The young artist was never again forced to sandwich her art into an office routine.

A few years later she decided that a year in Paris would further advance her study of the exacting techniques demanded of her medium; she took her savings in the same calm way and went off. Within two weeks of her arrival, she had gained an honorable mention at the prestigious Paris Salon.

International recognition continued to come to her even as miniature painting itself became less popular. In the 1920s and '30s, she added full-size portraiture to her art. She even reversed herself by accepting a commission to execute a full-scale painting from a family heirloom miniature of a lieutenant in the US Army during Jefferson's presidency.

While size had made Eda Nemoede Casterton's art practical for her, she never let it prevent her from realizing the full range and strength of the human figure in her portraits. So one can readily suppose that the life-size portrait of the scarlet-uniformed young soldier presented no problem to this miniaturist who knew how to paint ''in a big way.''