JOHANNESBURG -- Twenty years ago, Tito Zungu began decorating the backs of envelopes in his spare time and sold them to friends for 5 cents. Now collectors rush to buy his drawings at prices up to $1,500.

"I like the prices but it means that, these days, no African comes to me to buy -- only white people," said Zungu, who recently opened a one-man show in Johannesburg.

Zungu is one of the few South African artists to make the leap from decoration to art, from cattle kraals and urban townships to the world of galleries and critics and openings with printed invitations.

He comes from a shrinking pool of whittlers, weavers, painters and bead-stringers who cover walls with African designs and produce traditional tribal costumes.

While craftsmen in black communities gradually yield to Western tastes and mass-produced ornaments, Zungu is welcomed in Johannesburg as a discovery.

Gallery owner Vittorino Meneghelli praises the "freshness" and "incredible precision" of "one of the very few artists who owes nothing to art schools or imported trends."

Zungu turns out planes, trains and ships in ruler-straight lines drawn with ballpoint and felt-tip pens. His angular spaces are filled with solid patterns and careful rows of dots, reminiscent of the Zulu tribe's intricate beadwork.

He recently began to add living beings to his geometric visions of Zulu villages. Cows and people in pale shades now make a ghostly contrast to his usual strong colors.

Why planes, trains and ships? The 48-year-old artist said he became fascinated as a teen-ager by planes that flew over his father's small farm in Zululand, north of Durban, South Africa.

"If I was looking at an airplane climb, it made my heart feel something," he said. "I used to go up on a hill and look down at the beach, and I could see the ships very far away."

Zungu has spent much of his adult life working as cook and gardener at Roman Catholic institutions around Durban. About 1970, he came to the attention of Jo Thorpe, whose nonprofit African art center has introduced a number of black artists to a white clientele in the Indian Ocean port.

"Miss Jo asked me how much I was selling my envelopes for," Zungu said. "I said, 5, 12 and 15 cents. She said, carry on drawing and let's make it 10, 24 and 30 cents."

"I felt the prices were a bit low but I didn't want to overdo it," Thorpe said. "We started to sell on his behalf. The envelopes began going for 5 to 15 rand {$2.50 to $7.50}. Then he began doing actual pictures and won a prize in a national exhibition in 1971."

Zungu used a comb as a straightedge at the time and crayons to fill in blocks of color. Meneghelli offered to sponsor him so he could build a studio in his village and draw full time.

The project was never finished and Zungu, by his own choice, continues to do housework at a home for the elderly.

He draws slowly, going over and over the lines and colors until he achieves the desired intensity. He can take up to six months to finish and frame one item. The 20 items in his current show, including envelopes and drawings on paper, took five years to complete.