The following information formed the basis of a three-part article written by Julia Alexandra Mee for the Italian journal Grapevine (for more information visit their website)

I. Fresco Painting Today

In the sixteenth century, the painter, architect, and art historian Giorgio Vasari wrote in his influential biographies, Le vite dei più eccellenti pittori, scultori ed architettori, that, “Of all of the methods that the painters employ, painting on the wall is the most masterly and beautiful”.  Fresco painting has retained this reputation, largely due to the demands of the technique, which requires great diligence, working rapidly and resolutely, with just a limited palette.  One of the greatest periods of its use was during the Renaissance, and among the greatest exponents of the technique were Giotto, Masaccio, Fra Angelico, Ghirlandaio, Filippo Lippi, Botticelli, Filippino Lippi, Andrea del Sarto, Michelangelo, Raphael and even Giorgio Vasari himself.  

Fresco painters today face the ongoing problem of the transient nature of today’s society, and contemporary architecture which rarely takes into consideration the possible function of the wall space for wall paintings.  However, fresco painting has continually been employed by artists throughout the centuries to create magnificent monumental works of art, and recent years are of no exception.  

A continual desire to revive these techniques can be seen in the work of artists such as Pietro Annigoni (1910-1988) and his followers, one of whom is Silvestro Pistolesi whose frescoes can be seen in churches in Prato, Montecatini, Arezzo, Pisa, and also America.  At this very moment, the monumental fresco dedicated to San Ranieri in the Church of San Vito in Pisa, is being painted by Luca Battini (who studied under Pistolesi), proving that as public and private commissions continue to emerge, a fascination with this technique never ceases to arouse the deepest interest among art lovers.  

The recent request by Morena Guarnaschelli of the Borgo degli Artisti to display some of my demonstration panels of the fresco technique for a recent exhibition at the Casinò in Ponte a Serraglio, shows the ongoing interest.  Despite the difficulties in placing a fresco painting within an exhibition context, considering that the beauty of the technique is so integrated with their execution on the wall, I attempted to convey as clearly as possible an understanding of the technique, through the display of several demonstration panels, alongside a display board containing a written account of the process.  

As a painter and art historian I can conclude that there is no other pictorial technique which has given me more pleasure, and I only hope that this three-part article goes someway towards sharing this pleasure with others, encouraging a greater understanding and appreciation of one of greatest pictorial techniques, which we have in abundance in this beautiful area of Tuscany.

II. Fresco Painting - The Preparation of the Substratum

The term ‘fresco’ means ‘fresh’, and refers to painting on wet, that is, ‘fresh’ plaster.  The pigments (those which support the alkalinity of the plaster) are ground into powder, and mixed in water, lime water or lime milk, and are applied onto the surface whilst it is still moist.  Subsequently, as the calcium hydroxide (slaked lime) is exposed to the carbon dioxide in the air, it is transformed into calcium carbonate, fixing the colours within a durable surface, a process which is known as carbonatisation (Ca(OH)2 + CO2 = CaCO3 + H2O). 

In buon fresco (‘true' fresco), the preparation of the wall consists of the application of a number of layers of rendering.  Over the centuries, the thickness of the ground used in fresco painting has varied.  In the ancient wall paintings discovered during the excavations at Herculaneum and Pompeii, at least seven or eight layers of rendering had been applied, whilst during the Renaissance as few as two or three were employed.  

The first layer of rendering, known as il rinzaffo (il trullissatio or scratch coat), is applied onto the surface of the wall (which is preferably of bricks or stone) to regularise any irregularities and holes that are present.  The mortar is composed of slaked lime and clean river sand of a very large grain (or more traditionally, fragments of terracotta or pozzolana).  This rendering is left to dry out completely before the second layer is applied, the so-called arriccio (incrostature or sand coat), which is formed of a mortar of slaked lime and clean river sand of a large grain.  The entire compositional drawing known as the sinopia (after the red sinoper pigment used in the process) is executed on this layer.  When this has completely dried out, the intonaco is applied (the layer to be painted), which is composed of slaked lime mixed with clean river sand of a finer grain or marble powder, upon which the painting is executed.  This was sometimes followed sometimes by a thinner layer known as the intonachino or velo, which contains slightly more lime in the mortar. 

The renderings are applied in progressively thinner layers, with more lime added to the mortar with each successive layer, and the use of sand or marble powder of a progressively finer grain.  The last layer of rendering, the intonaco (and if present the intonachino), is applied in relatively small sections which have been predetermined according to the composition of the drawing.  At the beginning of the day, one section of intonaco is applied which is large enough to be painted and completed before the plaster becomes too dry at the end of the working day, hence the term giornata (from the Italian word ‘giorno’ meaning ‘day’).  

According to the Roman writer, architect and engineer Marcus Vitruvius Pollio, who recommended at least seven layers of rendering in his influential De Architectura (c.15 BC), there should be at least one layer of rinzaffo, three of arriccio, and three of intonaco.  This contributed towards a greater reserve of moisture in the ground, which allowed more time for the painting process, and as a result the intonaco was applied in pontata (large sections of plaster which corresponded to the scaffolding), examples of which can be seen in the wall paintings in Herculaneum and Pompeii.  

In later centuries, such as in the Renaissance, fewer layers were applied, sometimes only one of arriccio, upon which the drawing was executed, and one of intonaco.  Consequently, it was necessary for the intonaco to be applied in smaller sections (in giornate), since there was less time at the artists’ disposal for the painting process.  These giornate can be detected upon close examination of the surface of the frescoes.

III. Fresco Painting - The Painting Process

There are several methods for transferring the drawing in buon fresco, freehand directly on the wall, with the use of modelli (small squared drawings of the final composition), or with the use of a spolvero (‘cartoon’).  This last method was to become popular during the fifteenth century, and involved using a metal stylus to prick the contours of the full-size drawing, which was then placed against the wall, and pounced using a small pounce bag (a small bag made from a fine fabric containing powdered pigment).  This process left a series of dots on the surface of the wall which could be reinforced with a little powdered pigment mixed in water.  Another method for transferring the drawing, which became popular during the Renaissance, was that of incising with a metal stylus along the contours of the drawing which was placed on the ‘fresh’ plaster, leaving an impression on the wall. 

At the end of each day, the edge of the giornata is cut away at an angle of 45 degrees, ready for the application of the next day’s giornata.  The entire design needs to be thoroughly prepared, before the painting on the wall begins, with the giornata being applied methodically in predetermined sections.  For those who are right-handed, the application of the giornate commences at upper left part of the wall moving towards the upper right and then downwards, whilst for those who are left-handed, from the upper right to upper left and then downwards.  It is difficult to make design alterations and substantial changes with this technique, since any errors in execution are resolved by the removal of the section, and the intonaco is subsequently reapplied and repainted. 

The pigments were generally ground on a porphyry slab using a pestle of the same stone.  However, it is noteworthy to add that they were not all ground in the same way, some such as giallo di Napoli (Naples yellow) were not ground too much so as not to lose its strength of colour.  Traditionally, the pigments can be divided into three groups, those that can be washed and ground, those that can be washed but not ground, those that can be ground but not washed, and finally those that can be neither washed nor ground.  

The knowledge of the preparation of pigments is essential to the artist, particularly for the fresco painter, since only a limited range of colours support the alkalinity of the plaster, such as bianco di San Giovanni (lime white), il diaspro rosso (red jasper) il giallo di Napoli, malachite, and the earth pigments.  Other pigments, such as l’azzurrite, and l’oltremare needed to be applied a secco, that is, onto the dry wall with a tempera.  

I am indebted to Prof. Sergio Paolo Diodato, author of I Buoni Colori di Una Volta: Ricettario fotografico per conoscere e fabbricare pigmenti, leganti, vernici e materiali artistici antichi, direttamente dai trattati medievali, (Ortona, Edizioni Menabò, enlarged edition, 2012), for his continual support and knowledge, and I would like to acknowledge that a great deal of the technical information in this three-part article is the result of his lectures and publications, and those of his professor, the influential conservator Paolo Mora.