By definition is a fresco is a painting done on fresh plaster. The painting is completed immediately on freshly applied plaster before it dries. The very word used by the Greek to indicate this type of painting means humid, and this corresponds well to current terminology of fresco which in Italian means fresh.
In the Italian Renaissance fresco techniques were categorized as good fresco and dry fresco. In the fresco dryness, painting was made on the dry plaster with dyes having a base of adhesive or casein. In dry fresco, the painting was done on dry plaster with pigments having a glue or casein base. By drying the plaster a calcium carbonate is formed which incorporates the pure dyes, which are then diluted with only water.
During the Renaissance, it became customary to prepare a cartoon or drawing of the same size of the fresco to be executed in order to facilitate the organization and implementation of the work. This design was transferred to the wall by making small holes in the drawing and following the lines from the design.
This was then held up against the intonaco (coat of wet plaster) and colored dust our pounce as applied through the perforations to transfer the full design to the wall to be frescoed. Thus a large fresco was composed of many small sections. With each section corresponding to the amount of painting the artist could achieve before the plaster hardened. The sections were planned in a way that made joining the pieces together as inconspicuous as possible.
By it's very nature fresco painting does not allow for as much blending of colors as does oil painting. However, it provides clear luminous colors, and its endurance makes it ideal for majestic and decorative murals. However, since the technique is suitable in particular for dry climates it was employed only seldom in Scandinavian Europe.
There has been very little change in fresco techniques since it was first perfected in the 15th century by the great masters of the Italian Renaissance.
While there are some differing opinions about whether fresco techniques were actually used in Ercolano and Pompeii, it is clear that the tradition of true fresco painting in Italy was initiated by Masaccio. The exceptional artist who used his education and ingenious talent to fix on the walls of the Cappella del Carmine in Florence a complex set of images which is considered a true masterpiece of this technique. It was his work that inspired subsequent fresco artists including il Ghirlandaio, Pietro Perugino, Leonardo da Vinci, Fra Bartolomeo, Michelangelo and Raffaello.
Some general instructions about fresco painting is that one should absolutely avoid passing light colors over dark ones. Similarly one should not apply dark colors to areas which are to be light. When errors occur during painting the section is washed, and if possible additional plaster is applied and then painted over. Alternatively, the plaster must be knocked down, and the entire process must be started over the next day. If the fresco is one that will be observed from a distance, the colors should be decisive and daring. Realizing at a distance the weaker colors are simply not visible. The finalized fresco painting will lighten as it gradually dries. It takes at least three weeks to have a true indication of the approximate results.
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