Looking spontaneous takes a lot of preparation, children's book illustrator John Manders told students at Boyce Middle School in Upper St. Clair during the school's annual Author's Day this week.

On Monday and Tuesday, Mr. Manders told 5th- and 6th-graders about the steps he takes to illustrate a book and passed around examples of his work at each step.

Mr. Manders, who has a studio in Highland Park, has been drawing and painting ever since he was a very young boy in Syracuse, N.Y. A graduate of the Art Institute of Pittsburgh, he also took drawing classes at the Fashion Institute of New York and worked as a graphic designer until about 10 years ago, when he illustrated his first book. Since then he's illustrated about 30 more by several authors.

"His art just bounces off the wall. It's fun," said Nancy Moore, chairman of the PTA committee that organizes the event.

This is the first time the PTA has invited an illustrator to Author's Day, which has been held for at least 15 years. The invitation was suggested by PTA member Tisa Cassano-Janoski, who worked with Mr. Manders on postcards and posters for an Animal Rescue League of Western Pennsylvania fund-raiser about 10 years ago. She praised the detail and color in his illustrations.

Mr. Manders said he works closely with art directors, editors and designers.

He usually works closely with an author only when a book involves much historical research, such as "What You Never Knew About Fingers, Forks, and Chopsticks" by Patricia Lauber.

After an art director invites him to illustrate a book, Mr. Manders said, he reads the manuscript first to see if he likes the material. Some of the manuscripts he accepts allow him to draw whatever he wants, while those for children's textbooks give him specific instructions.

When he starts to draw, Mr. Manders said, he first does tiny "thumbnail" sketches. The size allows an artist to make changes more easily because there isn't as much detail. Once the art director accepts the thumbnail sketches, the artist puts all of them in order on a storyboard.

When he starts drawing a character, Mr. Manders said, he generally has to do several sketches because his head is "full of cliches."

To come up with something fresh, he told pupils, "you have to go outside of yourself" by reading or learning about the world in other ways.

There are several more steps before he starts painting. First, he traces enlarged copies of the thumbnail sketches using translucent paper, which allows him to see light and dark areas easily. Then the book designer sends him a layout combining the sketches and the words. Using transfer paper underneath the layout, he traces the images onto watercolor paper so that he can paint.

The paint he uses is gouache, an opaque water color, which he likes because it is too thick to see through. With the help of a plant mister to keep the paints moist, he works at his easel, preferring to stand because it helps him make "more energetic brush strokes." Toothbrushes and sponges help him flick paint to depict explosions and other effects.

Although painting the illustrations for one book may take two or three months, Mr. Manders said, the goal is for them to look spontaneous, as if he did the paintings in one afternoon.

When the paintings are finished, they are put together on press sheets, which go to the printer.

Mrs. Moore said the presentation taught pupils the importance of cooperation in book publishing. She said she wanted pupils to realize that "you don't go to your garret, put on your beret and work alone."