ON THE Indonesian island of Sumatra, a woman pregnant with her first child receives a piece of cloth called ulos ni tondi that carries the "soul force" of her ancestors. With it she wraps herself for protection during childbirth. In a land where pieces of woven cotton are believed to hold magical powers, this is the most importatnt gift she will receive from her family. It will guard her and her children for years to come.

For centuries the Indonesians have believed in the powers of textiles. Cloths of intricate design are workmanship figure prominently in their cherished customs.Although ancient customs have not survived everywhere, many flourish as they did centuries ago.

Marriages begin with an exchange of woven textiles. Bride and groom embrace in a customary wedding cloth to symbolize their union. A child is wrapped in gold and silk fabrics to receive his first haircut. The ill and infirm seek cures in water wrung from a cloth called the the kombong.

Ceremonial cloths escort the dead into a work free afterlife. The wise man stores textiles against his passing when they will envelope him in a huge bundle.

The textiles of Indonesia-a 3,500-mile archipelago in Southeast Asia-have been dispersed to collections around the world, many of the best to the Netherlands. Washington's Textile Museum worked more than two years to gather examples of this rich textile heritage. Through June 16 the museum displays more than 100 Indonesian textiles collected from several nations.

Lending pieces to the exhibit are four museums of the Netherlands, museums in Germany, Switzerland and England, plus the American Museum of Natural History, Boston's Museum of Fine Arts, the Brooklyn Museum, the Los Angeles County Museum of Art and the Metropolitan Museum of Art. The textiles represent private collections from New York to Los Angeles and that of Indonesian authority Raden Hardjonagoro, who made an unexpected donation of 21 batiks to the museum's collection at the show's opening.

Behind the exhibit, with help from the National Endowment for the Arts and the Charlotte Palmer Phillips Foundation in New York, is the soft-spoken Mattiebelle Gittinger, who became the museum's Research Associate for Southeast Asian textiles in 1975. Museum director Andrew Oliver Jr. initiated the exhibit after he took the post the same year.

Gittinger spent 2 1/2 years compiling information for the exhibit, writing a 200-page, heavily footnoted catalogue. She persuaded her couterparts in various lands to include their textiles and to travel here for a two-day symposium in which 50 authorities recently discussed the state of Indonesian textiles.

Curator of "Splendid Symbols: Textiles and Tradition in Indonesia," Gittinger arranged catalogue and exhibit according to the islands of origin: from Sumatra in the west to Ceram in the east.

Most pieces are the work of Indonesian artisans outside the capital island of Java. These from the 19th and 20th centuries, illustrate the Indonesian use of natural dyes and woven cotton and silks to make cloths of great ritual importance. Geometric, animal, human, mythical and sometimes ghost-like designs are the symbols of Indonesian custom.

The Sumatran tampan, or "ship cloth," marked life transitions, such as marriage, birth or death. Manned ships surrounded by a flurry of repeating patterns depict movement to another point in life's journey.

"The skills needed to produce them," writes Gittinger, "are now completely lost and apparently have been for three quarters of a century. . . . So many have appeared on Western markets in the past five years that it is doubtful any significant number remain in use in Sumatra today."

Cloths from Sumba were worn at funerals of noblemen. They helped send the soul to "heaven." The motif, either woven or made from rare shells and beads, is a female figure with arms uplifted. Thumbs and feet are large, out of proportion. The Sumbanese believed these were energy centers.

Some visitors will recognize the batiks of Jave. The art of making these fabrics has traveled widely. Joy Wood, a 35-year-old American who studied at the Batik Research Institute in Jogjakarta, and who demonstrates batiking during the exhibit, says that while some Americans may be familiar with batik as it is practised here, they will likely be amazed by the exquisite quality of pieces from the land of origin.

"In the United States, they think crackle (poorly defined lines caused by inferior waxes) is the big thing in batiking. In general, the Indonesians wanted smooth lines." (Some deliberately "cracked" their batiks, says Gitinger, to show they had no pretensions to royalty.)

Unlike other Indonesian textiles made of dyed threads woven together, batiks require dying fabric with a wax-resist method. Natural dyes, fine bees-wax and a canting tool are customary. The maker applies wax through the copper tip of the canting tool. The waxed fabric is dipped in dye, then the wax is removed. Repeating the process with different dyes produces multi-colored fabrics of magnificent delicacy. Some 30-foot-square pieces took months-even years-to produce.

Viewing these together, one sees why the Indonesian aristocracy valued them as treasures. Fathoming their workmanship proves to be something like attempting to comprehend the limitlessness of space. At times it seems hardly possible they are from the hands of mortals. They must be the work of gods.

Thousands of tiny dots and almost microscopically fine lines swirl and dance to form sometimes starkly contrasting images, at other times complicated designs not easily discerned from afar. Unlike pointillist paintings, their efeect is only heightened by close examination.

One shines bright as metal, the result of countless blue and beige dots playing one upon the other. Some show the influence of China and Japan: mythical Chinese animals, tigers, elephants and cloud scrolls; brilliant Japanese flower blossoms and butterflies.

This exhibit represents the best of Java's batik traditions. Some fear, however, the art is losing its charms to the demands of foreign markets and the methods of mass production.

Hardjonagoro, curator of the palace museum in Jakarta and recognized as one of the world's foremost batik artists, is one authority who sees dangers ahead unless batiking traditions are reinstated.

Batiks were not exported much before World War II. World markets have since expanded. Java has responded by increasing production and changing methods.

Once an art practised in private homes and the royal palace, batik "factories" are opening up, says Hardjonagoro, where the canting tool is replaced by block-patterned chops or even screens, producing fabrics some believe are of lesser quality.

"We are too far away already from our traditional way of life," he said. "We are too quick to look for something abroad. There's not enough attention to giving our younger generation a look at what we have. The only thing we can fight for is to teach the younger generation to appreciate what we have and to be proud of what we have."

Hardjonagoro hopes papers submitted by foreign experts and results of the symposium will convince Indonesian officials something must be done to stop encroachments upon batik customs.

"In Indonesia we have an expression called tunggak semi. It makes the picture of an old tree trunk that is dying yet sends up a young sprout. If things are not going like that, then they're not going as they should."