Cennino Cennini – The technique of egg painting on wood by Giotto – Duccio – Simone Martini – Pietro and Ambrogio Lorenzetti
The “Libro dell’Arte”, written by Cennino Cennini at the end of the 1300’s, is still the primary source for information about the techniques used in the Fourteenth Century. In the text, great importance is put on the preparatory drawing, the “true foundation of art”. In this phase of the work, the artist developed the composition separately, and then transferred it – already precise in every detail – to the final support. Or, beginning with an already clear idea, the artist could also develop the drawing directly onto the prepared panel. Various infra-red analyzes have revealed “pentimentos” (regrets) that lead us to understand how even during this period, the painter could correct and vary the initial idea. The composition was outlined with willow charcoal pencil and faces and drapery folds were shaded. The panel was then dusted and the re-worked drawing was retraced with “fresh water, and a few drops of ink”.
On the basis of the drawing, the wood panel was then prepared for the gilding process.
The indications in methodology given by Cennini do not always correspond to the practices in some of the workshops. In some of the paintings from this period the usual red tonality of the Armenian bole used for the preparation of the gilt background is missing. Instead, the ground is prepared following the older tradition using terre-vert. This color gives the gold leaf applied on top of it a very cold tonality, the surface is rougher and the burnishing becomes more difficult.
Cennini suggests that it is best to gild on humid days after having burnished the bole with a linen rag and then with the burnisher. The bole is then wet with a bit of water and egg white, and the gold leaf is laid upon it. The newly applied leaf is applied with a slight overlapping on the previous one.
Even the area in terre-vert, that Cennini recommends be painted in before beginning the flesh tones, does not always have to be done. Giotto, the artistic master from whom Cennini learned, breaks this rule. In fact, some of Giotto’s works are painted directly on the ground preparation. In these cases, there is not necessarily a detailed drawing or engravings in the ground preparation for reference, but simply a rough sketch in brown tones. In chapter LXVII of his Il Libro dell’Arte, Cennini makes references to three different methodologies. He advises the use of one of them in particular: “for Giotto, the great master, followed it”. Even in this case, the master’s works that have lasted until today seem to not support this affirmation. But, the technique can nevertheless be found in widespread practice in many other workshops, as for the example we propose here, in the Madonna and Child painted after a work executed by Duccio di Boninsegna.
Pictorial effects that were particularly refined and luminous could be obtained using the traditional technique of oil gilding. This technique could be used alone or in conjunction with the graffito technique of scratching, and with shell gilding for the decoration of smaller details. These techniques could also be used by following the ancient Byzantine tradition – as seen here – for modelling the Madonna’s entire cloak. The gold was applied on a uniform field of color composed of natural ultramarine blue. This technique is limited to the creation of the brightest highlights and executed by placing the gold on the outermost part of the drapery fold with close, tiny marks (lumeggiatura). From a decorative point of view, this highlighting was certainly effective. But because of their abstract and regular shape these highlights have a tendency to flatten out the figure. For this reason, they were quickly abandoned in the search for more effective three-dimensional effects.
As a mordant for the oil gilding, Cennini uses a mixture of boiled linseed oil, lead white and a variable quantity of resin copper meant to speed up the drying of the oil. At times, garlic juice was mixed with a bit of lead white and bole. With variations in the composition it was possible to modify the time needed between the application of the mordant and that of the gold. It was also possible to regulate the amount of highlight on the surface. Sometimes the mordant was built up three-dimensionally in an attempt to create an illusionistic effect and at the same time increasing the decorative effect. The mordant seen on the works by Duccio is always used quite thickly. This differs from the practice in Giotto’s bottega where – even though the same components were used (oil, lead white and earth pigments) – the result was a simple, flat gilded line.
Manfredi Faldi – Claudio Paolini
Painting by Ulrika Alton
Estratto da: Artis (Art and Restoration Techniques Interactive Studio), Direzione scientifica: Manfredi Faldi, Claudio Paolini. Cd Rom realizzato da un gruppo di istituti di restauro europei, con il determinante contributo della Commissione Europea nell’ambito del programma d’azione INFO2000.
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