YOU FIND him there most afternoons, painting at his little aluminum easel set up in a doorway of the defunct Woolworth store in Georgetown.

He works in temperas, and the paints stand in their little bottles on top of a tall stool along with a paper cup of water. He has a couple of palettes made from flattened foil pie-plates.

Around him is his furniture: two stacks of plastic milk crates. He keeps his sketch pad here, and sometimes he works on that, sketching with a light pencil in firm but delicate strokes.

Mostly, the paintings are small, 8-by-10s done on heavy paper from his pad. They are of buildings, the row across M Street: the Baers Building faithfully captured, with its dusty dark red brick and tall windows; Great Impressions, just up the street; Charlie's down on K Street.

Don Pierce spends his days here, working slowly and meticulously, ignoring the people who stride past on the busy sidewalk. A few of them pause, check out his works displayed on the windowfront.

"I get $75 to $85 for these," he says.

A sketch takes maybe eight hours, and a finished tempera painting two or three days. He can turn out a really special job if he has an extra day at it.

"I can do oils," he says. "I have to charge $200 for a commission. I work here unless I'm doing a commission."

He has produced about 400 paintings, he guesses, in the five years he has been working as an artist in Washington. He is from New Jersey, went to art school for two years after finishing high school, has a couple of adult children up north.

"I stay out of their lives," he says.

After he moved to Washington 12 years ago he had a series of jobs with the government, but now he paints for a living.

"I enjoy it," he says. He doesn't talk much.

Once in a while he will sketch a particularly handsome building on spec and try to interest the owner in buying his picture. But mostly he does frontal lineups of Washington's 19th-century office buildings.

"I like the contrast, the turn-of-the-century buildings next to the modern architecture."

Georgetown is the place for that, all right.

People talk to him occasionally, and then he stops and answers their questions, but when they are done he turns back to his small, neat, soberly colored world on paper.