The displayed works are accomplished through the use of ancient pictorial techniques passed on by Cennino Cennini in his treatise “Il Libro dell’ Arte” from 1437. The selection of the materials is of great importance in order to accomplish a superb level of craftsmanship in the final appearance of the replica. The icons are painted on wooden supports of poplar and cherry wood, while the selection of the painting materials, depends on medieval palettes of the Byzantine icon-painters.
First the wood was treated with animal glue and than covered with ground in few thin layers. After the ground has been polished, the preparatory sketch was applied and the carving of the figures was made. Furthermore, the gilder’s clay base was applied on which the golden or silver leafs were lay down. The underpainting was applied in the verdacio technique by the use of egg tempera. Than a delicate shading of flesh tones and drapery of the saints was made with fine thin brush strokes - the technique called trateggio. Finally the icons were protected with a thin layer of wax coating, which was fine polished.

Doratura a guazzo or water gilding presents a traditional technique that has been used since the thirteenth century by the great Italian and European artists. The preparation of the wood panel begins with application of a primer layer of hydrated calcium sulphate, also known as Bologna gypsum. Usually 2-5 coats of this gesso are required, and it has to be sanded very carefully to leave the panel perfectly smooth. The next step is the clay bole, which is mixed with water and glue. The bole affects the final color of the gilding. Therefore, it may be yellow (for bright gold), red (for dark gold), or black (for antique gold). When the panel is perfectly smooth the application of sheets of gold or silver leafs starts, by the use of a fine knife (gilder’s knife) and soft brush. Before this operation it is essential to spread a very fine layer of a mixture of alcohol and water.

Tempera, also known as egg tempera, is a permanent fast drying painting medium consisting of colored pigment mixed with a water-soluble binder medium (usually a glutinous material such as egg yolk or some other size). Tempera also refers to the paintings done in this medium. Tempera paintings are very long lasting, and examples from the first centuries AD still exist. Egg tempera was a primary method of painting until after 1500 when it was superseded by the invention of oil painting.

http://en.wikipedia.org/wiki/Tempera