Buon Fresco is Italian for ‘true fresco’. The interest in this technique is rooted in the notion of permanence through delicate means. Watercolor paint is applied to a wall made from plaster and one of the most famous examples of this is in the wall paintings at Knossos. The fascinating point to remember is that these watercolor paintings have lasted over 3000 years. The magic ingredient in this mix is lime.
Buon Fresco requires paint to be applied to a wet lime plaster base. As the lime carbonates and moisture evaporates, the pigment is entombed into a fine crystalline layer that develops on the surface of the wall. The effect is to as good as turn the lime plaster and accompanying pigment into stone, hence the incredibly long lasting quality of ancient frescos. Due to there being no modifying medium, the colors and clarity of the paint results in vivid images such as those on the ceiling of the Sistine Chapel in Rome.
The technique of Buon Fresco has to be one of the hardest, if not the hardest, of painting systems that has ever been attempted. Wet colors dry lighter than when first applied and different pigments react in different ways. A skilled painter is also working against the clock in that the water has to be drawn out of the plaster to give extra fluidity to the brush strokes. The fresco might take a month or more to fully dry and so calculations of tonal results have to be kept in mind.
I recommend the following book for readers who would like to know more about this fascinating technique and those like it.