This is Giotto's Adoration of the Magi and the artist has used both the Buon and Secco techniques in this painting.
Secco fresco is used on dry plaster, pigment is applied using egg or size as the medium and also as a binder for the paint. In the secco fresco technique the paint is not
absorbed into the structure of the plaster but forms a surface layer which tends to flake off and is therefore not so permanent as Buon fresco. Secco fresco is often used in conjunction with the buon method, secco is faster and allows for mistakes to be corrected.
A third type of fresco, mezzo-fresco, common at the end of the sixteenth century, was an intonaco that was painted when the surface was almost dry. The pigment only slightly penetrates the surface of the plaster retaining much of the colour that varied considerably when painting into wet plaster.
Artists of the renaissance worked in slightly different ways when working in fresco. Typically the artist would work from a top corner of the painting and gradually apply the paint from top to bottom, working a stage each day until completion. This method avoided damaging or splattering finished sections with paint.
Instead of using the red pigment sinopia for the under painting many artists used preparatory drawings on paper. The drawings would be held against the wall and the main lines pricked through, a bag of soot would be banged along the holes producing dots giving the outline of the work. Given that fresco painting did not allow mistakes to be easily rectified, the drawings became important in producing a coherent composition for the finished work.
Many of the worlds greatest cycles of paintings have been completed using fresco painting techniques and they include the example above from the Scrovegni Chapel.
Michelangelo's work in the Sistine Chapel is a fine (and very famous) example of the type of result that can be achieved with the medium, executed by a master craftsman at the height of his powers.