Steve Wolfe, age 13, of Marquette, Mich., for his question:

WHAT IS FRESCO PAINTING?

Fresco painting is a technique in which the artist paints on a plastered wall while the plaster is still damp. An artist who paints a wall picture on a dry plaster uses a process called secco painting.

Both inside and outside walls can be decorated by fresco artists. Their works add much to the beauty of buildings and homes. Fresco painting is especially well suited to decorating large walls in churches, government buildings and palaces.

A fresco painting, unlike many other paintings, has no glossy shine. A shine would make a fresco difficult to see from certain angles.

First, a wall must be carefully plastered before an artist paints a fresco on it. Usually several layers of plaster are applied. The first layer is somewhat coarse and the final layer, called the intonaco, is smooth and bright white.

Often the artist may apply the intonaco himself, rather than depend on a plasterer. He will not apply the intonaco over the entire wall at once. Instead, he will apply just enough for one days painting.

It is difficult to make changes in the picture while painting in fresco. Therefore, the artist prepares for his work carefully. First, he works out hi#s picture in color sketches. Next, he makes full sized drawings, called cartoons, on heavy paper. He hangs tracings made from the drawings on the wall. The artist produces outlines of the tracings on the surface of the final layer of plaster.

A fresco painter applies his paint onto the wall while the plaster is still damp. He uses colors made of dry pigment, mixed in most cases only with water. The plaster dries and hardens in about eight hours. The drying and hardening process seals the colors onto the wall.

The artist stops working when he runs out of damp, freshly applied intonaco.

At his next working session, the artist gives the final coat of plaster to the area next to the part of the fresco he finished previously. He then resumes painting, keeping the seam, or join, between the two sessions as neat as possible.

In many cases, platforms must be built so the artist can paint high sections of the wall or ceiling.

Fresco plaster bleaches many colors. Therefore, not all pigments used in other painting techniques can be used in fresco painting. Fresco painters get the best results from soft, not too brilliant colors. These artists frequently use grays, rust tones and tans. They also use fewer strong blues, greens, reds and yellows than do painters who work with other techniques.

Fresco painting was used in Egypt as early as 3000 B.C. and reached its greatest popularity from the 1200s through the 1500s. Italy was the center of fresco painting during that period. Michelangelo's Sistine Chapel in the Vatican is perhaps the most famous example of fresco painting.