Fresco
Wall painting done on fresh, wet lime plaster, so the colour becomes part of the wall.
Also: buon fresco, wall painting
In true fresco, pigments mixed only with water are brushed onto freshly laid lime plaster. As the plaster dries it hardens around the pigment, locking the colour into the wall. The painter can cover only as much as will stay wet for the day, and joins between days' work can often be seen. Only pigments that tolerate lime can be used. Painting on dry plaster with a binder is called secco; it is easier but less durable. The word fresco is Italian for fresh.