Final answer:
The painting process that involves applying pigment to wet lime plaster, making the paint part of the wall as it dries, is known as fresco.
Step-by-step explanation:
The technique described in the question, where water-based pigment is applied to freshly laid lime plaster, is known as fresco painting. The unique aspect of the buon fresco method involves the chemical reaction between the water-based pigments and the wet lime plaster, which makes the paint an integral part of the wall as the plaster sets. Not requiring a binder, the fresco technique has been utilized for thousands of years and is especially noted for its use in the creation of Renaissance period artwork in Christian imagery.