# Fresco: The Giornata, and Why Fresco Fails > Buon fresco sets pigment into the wall in one chemical reaction on a seven-hour deadline. What a painter adds after the plaster dries is what a conservator later loses. > The Study - 2026-08-02 > Canonical HTML: https://iconotheca.com/study/fresco-the-giornata-and-why-fresco-fails/ ## Key points - In buon fresco the paint is in the wall rather than on it: calcium hydroxide takes up carbon dioxide and locks pigment into calcium carbonate. - A giornata is one patch of intonaco and gives roughly seven to nine hours of work; Giotto's Scrovegni Chapel was calculated at 625 of them. - Blues went on a secco because lime is hostile to them, which is why skies and robes are the first passages lost from a cycle. - At Assisi the lead white in Cimabue's frescoes oxidised to lead dioxide, inverting his highlights into the darkest passages on the wall. ## Buon fresco is a chemical bond struck on a deadline ## The giornata is the real unit of a fresco, and it is legible on the wall ## Sinopia and spolvero: the drawing that lives under the picture ## The a secco layer is where cycles die ## At Assisi the true fresco turned on itself A fresco cycle is two paintings stacked on one wall, and they age on different clocks. What went into the wet lime is mineral and will outlast everything around it; what went on afterwards, which is usually the blue, the green and the gold, has the working life of any glue film on masonry. Assisi adds the harder lesson, that even the mineral half can turn, and that a pigment which was chemically ideal in 1290 can become its own opposite by 1990. Condition language about a fresco should always say which of those two paintings it is describing. ## Questions **How do you tell buon fresco from a secco on a wall?** By raking light and by loss pattern. Buon fresco has no separate paint film, so the colour sits flush in the plaster and losses follow plaster boundaries; a secco sits on top and fails by flaking, powdering and abrasion, usually in coloured islands rather than along giornata seams. Blues, greens and gold are the passages most likely to be secco. **Do giornate counts help with attribution?** Indirectly but usefully. Counting the daily patches gives the campaign's length, direction and rate of work, which constrains how large a workshop must have been and where a change of hand is physically possible. It cannot name a painter, and it is best used to test attributional claims rather than to generate them. **Can the blackened lead white at Assisi be reversed?** Research into reconversion of oxidised lead white exists, but this is not a cleaning problem. The original pigment has become a different compound within the paint layer, so any treatment is a chemical transformation of original material rather than the removal of something added, and the conservation profession treats that threshold with appropriate caution. **Why is fresco detachment no longer standard practice?** Because it destroys the relationship between the paint and its wall and creates a new, fragile object mounted on a modern support. It was used in the twentieth century after damage such as the 1944 destruction at Pisa's Camposanto, and it produced the sinopie now in the Museo delle Sinopie, but current practice stabilises in situ wherever possible. ## Sources - [1] Wikipedia, 'Fresco': arriccio and intonaco, the carbonation equation, seven to nine hours' working time, mezzo-fresco, a secco and blue pigments, spolvero. Tertiary source; replace with conservation literature on lime plaster technology. - [2] Wikipedia, 'Scrovegni Chapel': campaign of 25 March 1303 to 25 March 1305, calculation of 625 giornate, workshop of about forty, interior dimensions. Tertiary source. - [3] Wikipedia, 'Sinopia': hematite-based earth from Sinop, drawing on the arriccio, strappo and stacco detachment, Camposanto Pisa 1944, Museo delle Sinopie. Tertiary source. - [4] Wikipedia, 'The Tribute Money (Masaccio)': c. 1425, 247 x 597 cm, losses of a secco passages recorded in the 1981-1990 restoration. Tertiary source. - [5] Wikipedia, 'Sistine Chapel ceiling': 1508-1512, giornate and west-to-east progression, removal of later a secco retouching and gold in the 1980-1994 restoration. Tertiary source. - [6] Wikipedia, 'The Last Supper (Leonardo)': c. 1495-1498, 460 x 880 cm, tempera over gesso, pitch and mastic with a lead white underlayer, flaking by 1517, restoration campaigns to 1999. Tertiary source. - [7] E. Avranovich Clerici et al., 'Multi-Scale X-ray Imaging of the Pigment Discoloration Processes Triggered by Chlorine Compounds in the Upper Basilica of Saint Francis of Assisi', Molecules, 17 August 2023, doi 10.3390/molecules28166106. - [8] Wikipedia, 'Cimabue': dates c. 1240-1302, the Upper Church cycle at Assisi and its condition. Tertiary source. - [9] Wikipedia, 'The Mocking of Christ (Cimabue)': egg tempera and gold leaf on poplar, 25.8 x 20.3 cm, infrared reflectography of the underdrawing. Tertiary source; replace with the Louvre acquisition file.