which technique is being used when paint is applied to a dry plaster wall?
In the dry plaster or fresco secco technique, pigments are usually mixed with water, although other substances might also be used. The paint is then applied to a dry plaster wall which has been wetted down with water. Since the plaster is relatively dry, it is non-absorbent, and the pigment adheres to the surface of the plaster. This technique differs from true fresco (described below) in several ways. The colors tend to flake off the surface of the plaster.