What light is thrown on the activity of the panel painter's workshop in Cennini's Il Libro dell'Arte?
The workshop (or bottega) in Cennini's lifetime (1370-1440) operated within a culture very different from today. In order to understand the activity within the panel painters' workshops it is necessary to understand the society in which they operated.
Each workshop was a family business controlled by a master who was in turn a member of a guild. The painting business was regarded simply as another craft like building or woodworking and the workshop was part of a closed shop system for controlling the businesses within a city. During Cennini's lifetime the role of the artist started to change although it was not until the beginning of the sixteenth century that certain artist started to be seen as socially significant.
Cennini's book, Il Libro dell'Arte, provides a practical manual on the basic techniques required by the artist. It does not describe what a workshop was like to work in or how to run a panel painting business. There are also a number of techniques not covered, such as perspective, painting on stretched canvas, chiaroscuro and sfumato as they had not been developed. Oil painting was on the increase and it is covered briefly in the book but only because it is "as the Germans are much given to do" (Cennini, p. 57). The book therefore comes at a turning point between the techniques of medieval art and the developments of the renaissance. Cennini foresees the renaissance in so far as he recognizes the need for imagination in art and the attributes of art that will lead to it gradually increasing in status as it is seen as a liberal art rather than merely a craft.
The painter had to be a member of a guild (a 'master') in order to operate his business. The guilds were very powerful and enabled the masters to operate a cartel. They regulated prices and quality, prevented any member cornering the market in materials, regulated competition, and forbade advertising and the sale of a master's work outside the city.
In the first half of the fourteenth century Florence had seven great guilds (Arti Maggiori) and fourteen lesser guilds (Arti Minori). The members of the great guilds included the wealthiest and most powerful men of the city who were known as the popolo grasso (fat people). In the early fourteenth century painters became members of The Arte dei Medici e Speziali (guild of physicians and pharmacists) probably because painters' pigments were chemical, minerals, and plants that were ground in the same way as materials for medicines. Also, doctors and painters both had Saint Luke as their patron saint because he was both an artist and a physician. By the end of the fourteenth century painters had formed their own branch of the guild and by the late sixteenth century academies had been formed to train and represent artists, and the guild system began to die out.
The painter's business was often associated with a small number or even a single patron and the patron could be a church, a civic unit, or a wealthy individual. Painting served a well defined purpose such as completing an altar or making a wedding present. The master painter needed to earn a living by doing a good job, using quality materials and satisfying the requirements of the patron. This meant that the role of the artist in the production was less important than the final effect; with a large workshop of experienced apprentices the master could leave much of the mechanical work to the others. For a higher price he would do more of the work, with assistants preparing the panel and colours and doing the background painting. For a lower price he would draw the composition and supervise the assistants.
Contracts defined exactly what the patrons required in terms of the subject, number of people, size of people, composition, the use of expensive materials such as ultramarine and gold, the time and involvement of the master and the delivery date and manner of payment.
A workshop would not just carry out panel painting but would produce all the articles they were allowed to produce within the strictly defined guild rules. There are few paintings or drawings of a painter's workshop and so it is difficult to form a clear picture of what they were really like. However, Figures 1, 2, 3 and 4 give some idea even though they are a later period, a different country and stylized. Figure 1 shows a crowded room with activities ranging from the master in the centre painting a large religious painting, a journeyman drawing a client, an apprentice copying a bust and others mixing paints and grinding pigments. In some workshops as many as thirty apprentices and assistants would assist the master painter. The master would accept commissions for paintings and other items, including the design of jewellery, festival banners, and vestments for clergymen.
1. The purchase of a clean, dry wooden panel from a carpenter. The strict guild system meant that it was illegal for one guild to undertake any work that was in the province of another guild so the wooden panel would have to be purchased, not made.
2. Fill any holes with sawdust mixed with glue. Hammer in any nail ends and cover them with tinfoil to stop rust.
3. Cover the panel with size using a diluted size first, followed by two strong coats.
4. Glue canvas to the panel using size.
5. Cover the panel with a thick layer of warm plaster of Paris and size (called gesso grosso).
6. Cover the panel with a thin layer of thoroughly slaked plaster mixed with warm size (gesso sottile).
7. Scrape down the panel using a straight edge and charcoal to reveal the high areas and a flat scraping tool to reduce their height.
Note that the above process would take about 10 days in a warm climate because of the drying times between each step. The final step is the most labour intensive unless the panel has a complex moulding when steps 5 and 6 would also be lengthy.
The next step in painting a panel involved preparing the pigments, sketching the painting on the panel and then applying the paint. Preparing the pigments was a time consuming process as it involved grinding the materials for hours or even days. Cennini describes how various types of black, red, yellow, green, white and blue are prepared. He mentions the use of indigo but not how it is prepared. The assumption that renaissance workshops had to prepare all their own pigments from scratch is dispelled by Cennini. For example, his advice reads, "A color known as vermilion . . . is made by alchemy. . . I am leaving out the system for this because it would be too tedious. . . I advise you rather to get some of that which you find at the druggists' . . . so as not to lose time." (Cennini, p. 24)
The above process is for the painting of tempera on prepared wooden panels. The painting of canvas stretched on a wooden frame did not start until later and was associated with the increasing use of oil painting. Karel van Mander in The Painter's Book (1604) states that oil painting was invented in 1410 by Jan van Eyck and his brother Hubert. Van Mander describes how van Eyck kept the secret of oil painting secret until he died in when he passed it on to Roger (Rogier van der Weyden). Vasari adds that Antonello da Messina (ca. 1430-1479) travelled to Bruges and learned the secret. However, Cennini writing between 1390 and 1400 describes oil painting (that is mixing pigments with linseed oil as well as using linseed oil as a varnish) "as the Germans are much given to do" (Cennini, Chapter LXXXVIIII p. 57). This apparent contradiction has been explained by speculating that it was the precise formula van Eyck's found that gave oil paints their superiority over tempera in terms of drying time, ease of application and their improved ability to create detail with a clarity, luminosity and depth of colour not possible with tempera. Van Eyck was the first to consistently use thin pigmented oil glazes and varnishes and in this sense the art of oil painting could be said to have been created by van Eyck.
What we think of as the difficult part of painting, creativity, imagination and emotional intelligence translated into form, seems a relatively small part of the overall effort described by Cennini and is described in straightforward terms. The overall process described by Cennini sounds more like a description we might read today on the techniques required by a bricklayer. However, as few prepared materials were available learning all the techniques required a long period as an apprentice.
An apprentice (garzone in Italian) typically started with their master at the age of 15, they were typically male and the master was often paid to take on the apprentice, usually by his parents. The apprenticeship lasted about seven years and the next stage was to become a journeyman, who was paid a daily salary and who had to produce a 'masterpiece' to satisfy the guild that he was a master craftsman and thus become a member of the guild. This was not easy because the journeyman had to work on his own time to produce the masterpiece and Sunday was the only day he did not work from sunrise to sunset. He had to use his own tools and raw materials that he had purchased from his salary. Then if he did produce the piece, the guild would only vote for him if there was enough work to go round.
Other writers also describe the apprenticeship system. For example, Vasari tells an amusing story of how the apprentices of Fra Fillipo Lippi played a trick on him by putting hats on his angels, indicating there was often a good relationship between master and apprentice.
By the time of the High Renaissance society and the role of the artist was changing rapidly. The artist was increasingly seen as possessing 'genius' (an attribute that did not appear until the renaissance) and was someone who, if they had genius, could converse with popes and kings. As part of the fight for a new role for the artist Leonardo challenged the definition of knowledge according to which the seven liberal Arts represented the highest form. The seven liberal arts included poetry and music but painting was relegated to the mechanical arts and was considered inferior. Leonardo is at great pains to show the superiority of painting, for example claiming "Painting excels and ranks higher than music" (da Vinci, The Notebooks of Leonardo Da Vinci, p. 194-204). By this time, when he talks of the artist's studio he is thinking more of a place for contemplation rather than a workshop as he recommends one studies alone ("the painter…ought to remain solitary") unless a suitable companion can be found, but he also sees benefits in the competitive environment of a studio ("drawing in company is much better than alone") as shame and envy will spur you to better work (ibid p. 216-227).
The sophistication of Leonardo's views expressed some one hundred years after Cennini highlights the developments that took place during the renaissance. However, Leonardo's work was built upon the sound practices of the craftsmen of Cennini's day. It is clear from Cennini's book that Italian workshop's of the period produced panel paintings under conditions of highly developed craftsmanship and little distinction was made between craft and art. Their sound knowledge of technique enabled them to cope with the difficulties and limitations of each material and medium and yet exploit its beauty to the full and their knowledge often insured the permanency of their work.
Alberti, L. B. On Painting (London: Penguin Books 1991, translated by Cecil Grayson)
Burke, P. The Italian Renaissance: Culture and Society in Italy (Cambridge: Polity Press, 1995)
Cennini, C. The Craftsman's Handbook "Il Libro dell'Arte" (London: Dover Publications, 1954, originally published by Yale University Press 1933, translated by Daniel V. Thompson, Jr.)
Cellini, B. The Life of Benvenuto Cellini (Geneva: Heron Books, 1968, translated by John A. Symonds)
Da Vinci, L. The Notebooks of Leonardo da Vinci (Oxford: Oxford University Press, 1952, reissued 1998, selected and edited by Irma A. Richter)
Da Vinci, L. Leonardo on Painting (New Haven and London: Yale University Press, 1989, edited and translated by M. Kemp and M. Walker)
Da Vinci, L. 'Extracts from his Notebooks' in P. Elmer, N. Webb and R. Wood (eds) The Renaissance in Europe: An Anthology (New Haven and London: Yale University Press in conjunction with The Open University, 2000)
Freedberg, S. J. Painting in Italy 1500-1600 (Middlesex: Penguin Books, Second Edition 1986)
Paoletti, J. T. and Radke, G. M. Art in Renaissance Italy (London: Laurence King, 2001)
Welch, E. Art in Renaissance Italy 1350-1500 (Oxford: Oxford University Press, 1997, reissued 2000)
Van Mander, K. 'The Painter's Book' in E. Fernie (ed) Art History and its Methods (London: Phaidon Press, 1995, reprinted 2002) pages 43-57
Vasari, G. The Lives of the Artists (London: Penguin Books, 1965, reprinted 1977)
Figure 1: Jan van der Straet (1523-1604), Painter's Studio
Figure 2: Saint Luke
Figure 3: Niklaus Deutsch (1484?-1530) St. Luke painting the Virgin,1515
Figure 4: Mercury, Engraving Attributed to Baccio Baldini, c. 1460
 The modelling of volume by the use of contrasting light (chiaro) and dark (oscuro)
 Italian for 'smoky' and used to describe an oil painting technique in which the artist coats the objects in a picture with layers of very thin paint to soften edges and blur shadows
 Cennini, page 1, "…an occupation known as painting, which calls for imagination, and skill of hand, in order to discover things not seen, hiding themselves under the shadow of natural objects, and to fix them with the hand, presenting to plain sight what does not actually exist."
 The seven liberal arts classically consisted of the trivium of Grammar, Rhetoric and Logic and the Quadrivium of Arithmetic (numbers), Geometry (numbers in space), Music (numbers in time) and Astronomy (numbers in space and time)
 Cennini, page 1, "And it justly deserves to be enthroned next to theory, and to be crowned with poetry. The justice lies in this: that the poet, with his theory, though he have but one, it makes him worthy, is free to compose and bind together, or not, as he pleases, according to his inclination. In the same way, the painter is given freedom to compose a figure, standing, seated, half-man, half-horse, as he pleases, according to his imagination." It can be seen from this quote that the understanding of what constitutes a liberal art had changed from the time of Pythagoras and Cennini was trying to cast off the mantle of manual work by emphasising the role of imagination. A stronger argument for Pythagoras would have been to argue that painting (in particular perspective) was a branch of Geometry as it represents numbers in space.
 Inevitably a master of a workshop was a man. A women married to a master could became a master if he died although this rule was probably more to do with the inheritance and continuity of the business as there is no evidence that the wife of a master was trained in the workshop. The daughter of a master was sometimes trained in his workshop (e.g. Lavinia Fontana, 1552-1614) or a woman could learn to paint in a nunnery (e.g. Caterina dei Vigri, 1413-1463) or even learn through the conventional route (Properzia de Rossi, born either c.1490 or 1450 and died 1530) but the number of renaissance women artists was very small. It is possible that as it was indoors work many more women worked in the business but their work was passed off as that of their brothers and cousins.
 Government buildings, guild buildings, hospitals, monasteries down to even the smallest churches required works of art and so there was a continual source of business. In addition, the city states were growing and increasing in wealth and the number of wealthy individuals was increasing.
 Individual patrons saw many benefits in commissioning paintings - they demonstrated their wealth and power, they were seen to be good citizens doing their civic duty, they improved their standing in society, they could expiate a sin, reduce the time they thought they would spend in purgatory, leave behind a reminder of themselves as a form of immortality and produce something they liked.
 The commissions were typically religious although some were secular, such as Allegory of Good Government, Palazzo Pubblicio, Sienna (1338-40). At this period even such secular paintings contained religious iconography such as visual references to the Last Supper. Later lifelike figures of donors appeared on altarpieces, saints were painted with the features of contemporaries and scenes were set locally. By the end of the fifteenth century Leonardo da Vinci, Sando Botticelli and many other were painting mythical subjects and portraits.
 A practice still used by some artists today, for example Bridget Riley
 See Paoletti, p. 24 for an example of part of a typical contract
 The "nicest and neatest occupation which we have in our profession" Cennini p. 64.
 Note that the panel can be surrounded by a moulding and the steps are applied to the panel and the moulding (except for step 4, although Cennini does not make this clear).
 Whitewood, poplar, linden or willow
 Between each stage the panel must be allowed to dry and any lumps must be removed with a knife
 Thus technique is still used in engineering to create a perfectly flat metal plate using 'engineer's blue' rather than charcoal.
 Note that the process is similar to painting a wooden panel today which requires knotting, priming, undercoat and two topcoats with drying between coats (although 'one coat' paints now combine undercoat and topcoat).
 Black is made from a soft, black stone, burned vine twigs, burnt almond shells or linseed oil soot.
 Red is either sinoper or porphyry (a shade of red ochre, a red iron oxide), cinabrese (another shade of red earth, like sinoper but 'the lightest sinoper…only used in Florence'), vermilion (cinnabar or mercuric sulphate, made by heating mercury and sulphur in a retort), red lead (made by heating white lead in air, but its is not suitable for frescos), hematite (a naturally occurring ore of iron oxide), dragonsblood (a reddish resinous substance extracted from outside of cherry-size berries) or lac (produced from the resin of certain trees from India that have been stung by certain insects, also called lake, lacca, gum lac of India)
 Yellow is either ochre (found in seams in the ground), giallorino (also called massicot, made by heating white lead gently), orpiment (arsenic tri-sulphide, found near geothermal vents and poisonous), realgar (arsenic disulphide, very poisonous), saffron colour extracted from a herb using lye (a strong alkali prepared by mixing warm water with ashes) or arzica (a yellow lake pigment made from wild flowers)
 Green is either terre-verte (a natural earth colour), malachite (a natural stone containing copper silicate, Cennini calls it artificial and suggests buying it ready made), or made by mixing orpiment and indigo (although Cennini does not describe how to make indigo), blue and giallorino or orpiment and ultramarine blue.
 White is either white lead (made from a complex process of heating hundreds of earthenware pots using dung for a month, each pot has vinegar in the bottom and a coil of lead above on a shelf. At the end of the process the lead has mostly turned in to white lead through the action of acetic acid vapour and carbon dioxide) or lime white (made by heating limestone (calcium carbonate) to produce quicklime (calcium oxide) which mixed with water produces slaked lime (calcium hydroxide), which further mixed with water gives lime white)
 Blue is either azurite (occurs with malachite, copper carbonate, an inexpensive greenish blue. During the Middle Ages and renaissance, azurite was the most important pigment in European painting) or ultramarine blue (described by Cennini as "illustrious, beautiful, and most perfect", made by grinding lapis lazuli and then extracting the colour using a resin, mastic and wax mixture followed by lye)
 A method of painting in which the pigments are mixed with an emulsion of water and egg yolks or whole eggs (sometimes glue or milk)
 "…he became very intimate with the said Johann [Jan van Eyck], making him presents of many drawings in the Italian manner and other things, insomuch that the latter, moved by this and by the respect shown by Antonello, and being now old, was content that he should see his method of colouring in oil; wherefore Antonello did not depart from that place until he had gained a thorough knowledge of that way of colouring, which he desired so greatly to know." Vasari, Lives of the Artists, Antonello da Messina
 "When you have put in a year, more or less, at this exercise", Cennini p. 8
 Cennini's apprentice Jacopo di Poggibonsi started when he was 13 and Andrea Mantegna (1431-1506) was apprenticed at age 11, Andrea del Sarto was seven, Titian was nine, Mantegna and Sodoma 10, Paolo Uccello was 11 and Michelangelo was 13 when he was apprenticed to Ghirlandaio. However, Botticelli was still at school when he was 13, while Leonardo was not apprenticed to Verrocchio until he was 14 or 15. See Peter Burke: The Italian Renaissance: Culture and Society in Italy (Cambridge: Polity Press, 1995), pp. 51-56
 In Venice at the time the minimum apprenticeship was five years followed by two years as a journeyman
 "It is not without the impulse of a lofty spirit that some are moved to enter this profession, attractive to them through natural enthusiasm. Their intellect will take delight in drawing, provided their nature attracts them to it of themselves, without any master’s guidance, out of loftiness of spirit. And then, through this delight, they come to want to find a master; and they bind themselves to him with respect for authority, undergoing an apprenticeship in order to achieve perfection in all this. There are those who pursue it, because of poverty and domestic need, for profit and enthusiasm for the profession too; but above all these are to be extolled the ones who enter the profession through a sense of enthusiasm and exaltation.", Cennini p. 2
 "The basis of the profession, the very beginning of all these manual operations, is drawing and painting. These two sections call for a knowledge of the following: how to work up or grind, how to apply size, to put on cloth, to gesso, to scrape the gessos and smooth them down, to model with gesso, to lay bole, to gild, to burnish; to temper, to lay in; to pounce, to scrape through, to stamp or punch; to mark out, to paint, to embellish, and to varnish, on panel or ancona.’ To work on a wall you have to wet down, to plaster, to true up, to smooth off, to draw, to paint in fresco. To carry to completion in secco: to temper, to embellish, to finish on the wall." Cennini p. 3