Secco: Painting on Dry Plaster, Less Durable Than Buon Fresco

When the eighteenth-century antiquarian Johann Joachim Winckelmann saw paintings from the recently excavated ruins of Herculaneum, he noticed something troubling. When the paintings were cleaned with water, the pictorial layer came off. The colors washed away. This was not buon fresco, where the pigment is chemically bonded to the plaster. This was secco, painting on dry plaster, and it was far more fragile than anyone expected. The discovery that Roman wall paintings used secco techniques alongside fresco changed the understanding of ancient painting methods and highlighted the fundamental tradeoff of the technique: flexibility in exchange for durability.

Secco, or fresco secco, is a wall painting technique in which pigments mixed with an organic binder are applied to dry plaster. Unlike buon fresco, where the pigments become chemically integrated with the wet plaster, secco paint sits on the surface of the wall, held in place by the binder. The technique is also called a secco (Italian for "on dry") or fresco finto (false fresco). The binders used include egg tempera, casein, animal glue, oil, and lime water. The result is a painting that is less durable than buon fresco but offers a longer working time, a wider range of pigments, and the ability to make corrections.

This entry covers what secco is, how it differs from buon fresco, its history from antiquity to the Renaissance, and how to identify it in a mural.

What Is Secco and How Does It Differ From Buon Fresco?

The difference between secco and buon fresco is chemical. In buon fresco, pigments ground in water are applied to wet lime plaster. As the plaster dries, the calcium hydroxide reacts with atmospheric CO2 to form calcium carbonate, trapping the pigments inside the crystalline matrix. The painting becomes part of the wall. In secco, the plaster is already dry. The pigments are mixed with an organic binder, such as egg, glue, casein, or oil, and applied to the surface. The binder holds the paint to the wall, but the bond is mechanical, not chemical. The paint sits on top of the plaster rather than being embedded within it.

This difference has practical consequences. Buon fresco is permanent but unforgiving. Once the plaster dries, the painting cannot be changed without cutting out the plaster and starting over. The painter must work quickly, completing each giornata before the plaster sets. The palette is limited to alkali-stable pigments, which excludes many blues, greens, and reds. Secco solves all of these problems. The painter can work at any pace, because the plaster is already dry. Any pigment can be used, because the organic binder protects the pigment from the alkaline environment. Mistakes can be painted over. Details can be added with precision.

The tradeoff is durability. Because the paint is on the surface rather than inside it, secco is vulnerable to moisture, abrasion, and the deterioration of the organic binder over time. A 2024 study published in the Journal of Cultural Heritage analyzed non-restored Pompeian mural paintings using optical microscopy, reflectance transformation imaging, micro-EDXRF, micro-FTIR, and direct temperature-resolved mass spectrometry. The research identified a protein-based medium, most probably egg, used to execute the secco layers over fresco backgrounds. The study confirmed that secco painting in Pompeii was used for the uppermost layers and details, applied over a fresco foundation. Read the full study at ScienceDirect.

A variation called lime secco involves mixing pigments with lime water or lime milk and applying them to dry plaster. The lime water reactivates a thin carbonation process on the surface, creating a weak chemical bond that is stronger than pure organic binder but weaker than true buon fresco. This technique, also called mezzo fresco, occupies a middle ground between the two methods.

Origins and History

Secco painting is ancient. The earliest wall paintings from Egypt, Mesopotamia, and the Aegean used secco techniques, because the dry climates and the nature of the wall surfaces made buon fresco impractical. Egyptian tomb paintings, dating back to the third millennium BCE, were executed on dry plaster using tempera binders. The technique persisted throughout the ancient Mediterranean world.

In the Roman world, secco was used alongside buon fresco. A 2023 review published in the Journal of Cultural Heritage traced fresco wall painting techniques across the Mediterranean from antiquity to the present, noting that "the predominant technique used in Roman mural paintings seems to have been fresco. However, the application of organic binders to extend the uppermost layers has been discussed by many scholars since the first excavations in the Vesuvian area." The review highlights the difficulty of distinguishing between fresco and secco in ancient paintings, because the organic binders used in secco deteriorate over time and are difficult to detect. Read the full review at ScienceDirect.

In medieval and Renaissance Italy, secco was used as a supplement to buon fresco rather than a replacement. The standard practice was to paint the main composition in buon fresco, then add details, corrections, and pigments that were incompatible with wet lime using secco. The Ars Pictoria guide explains that "since the early days of wall painting, artists often combined a fresco and a secco techniques, completing a composition begun on fresh plaster with glazes or final touches applied a secco, using media such as glue or egg tempera. Some pigments (such as azurite, vermilion or lake for example) would be altered or damaged by the strongly alkaline lime and were typically applied a secco." Read the full guide at Ars Pictoria.

The Sistine Chapel provides a famous example. Michelangelo painted the ceiling primarily in buon fresco, but the blue backgrounds of some scenes were painted a secco using ultramarine or azurite mixed with a glue binder. The 1980-1994 restoration of the Sistine Chapel had to treat these secco areas differently from the buon fresco, waterproofing them before cleaning the fresco sections to prevent damage. The restoration report, published on ResearchGate, notes that "before proceeding to clean the parts painted in buon fresco, the few parts painted in dry fresco, including parts of the retouching performed by previous restorers, were waterproofed with Paraloid, so that the water used for the fresco did not do any damage." Read the full report at ResearchGate.

Key Artists and Works

Roman Wall Painters (c. 100 BCE - 79 CE)

The wall paintings of Pompeii and Herculaneum, preserved by the eruption of Mount Vesuvius in 79 CE, are the largest surviving body of ancient secco painting. The paintings combine buon fresco backgrounds with secco details and finishes. The Villa of the Mysteries, the House of the Vettii, and the House of the Tragic Poet all show the combination of techniques. The secco layers have deteriorated more than the fresco foundations, which is why some Pompeian paintings look faded or incomplete where the secco paint has flaked away.

Michelangelo Buonarroti (1475-1564)

Michelangelo used secco for specific passages in the Sistine Chapel where buon fresco was not feasible. The blue lapis lazuli backgrounds in the Last Judgment (1536-1541) were painted a secco, because the pigment was too expensive and too unstable in wet lime to risk in fresco. These secco passages are more vulnerable than the surrounding buon fresco and have required special attention during restoration.

Giotto di Bondone (c. 1267-1337)

Giotto's Arena Chapel frescoes (1303-1305, Padua) are primarily buon fresco, but analysis has shown that some details, particularly the blues in the skies and certain highlights, were added a secco. These secco additions have largely deteriorated, leaving the skies with a grayish, washed-out appearance where the blue pigment has flaked away.

Byzantine Icon Painters

Byzantine wall paintings, found in churches throughout Greece, the Balkans, and Russia, frequently used secco techniques. The dry, stable climate of many Byzantine churches and the nature of the wall surfaces made secco a practical choice. The frescoes at the Church of St. Panteleimon in Nerezi (1164, North Macedonia) combine buon fresco with secco details, and the secco passages have survived less well than the fresco.

Indian Wall Painters

The Silparatna, an eighth-century text by Kumaradeva, gives a detailed account of secco painting technology in India. The text describes the preparation of surfaces, the mixing of pigments with binders, and the use of five types of brushes. Indian wall painting traditions, including the paintings at Ajanta (second century BCE to fifth century CE), used secco techniques extensively, often with tempera binders on dry plaster.

How to Spot Secco in a Painting

Identifying secco in a mural requires looking for signs of surface paint rather than embedded paint. If the paint layer is flaking, powdery, or visibly sitting on top of the plaster rather than integrated with it, it is likely secco. In well-preserved examples, the distinction is harder to see, but secco paint often has a slightly different surface quality than buon fresco: it can be glossier if an oil binder was used, or more matte if egg tempera was used.

Look for areas where the paint has been lost while the surrounding plaster remains intact. In buon fresco, the paint and plaster deteriorate together, because they are the same material. In secco, the paint can flake off while the plaster underneath remains sound. This is why many ancient wall paintings look like they have blank patches: the secco paint has fallen away, exposing the bare plaster.

The Pompeian studies provide the clearest examples. In the House of Marcus Lucretius, the fresco backgrounds are well preserved, but the secco details on top have largely disappeared. The contrast between the durable fresco and the fragile secco is visible throughout the Pompeian archaeological site.

Related Techniques

Secco is the counterpart to buon fresco, the technique of painting on wet plaster. The two were almost always used together in Renaissance mural painting: buon fresco for the main composition, secco for details, corrections, and pigments incompatible with wet lime. Mezzo fresco, a hybrid technique, involves applying pigments mixed with lime water to partially dry plaster, creating a bond stronger than secco but weaker than buon fresco. Secco also connects to tempera painting, since egg tempera was the most common binder used for secco work. Gold leaf application on wall paintings was also a form of secco, using mordant gilding on dry plaster. For broader context, read our blog post on how to read a painting, or explore our post on art in architectural settings.

See Secco in Person

The best place to study secco is Pompeii, where the combination of buon fresco and secco is visible in hundreds of wall paintings. The Villa of the Mysteries is the most famous example, but the houses along the Via dell'Abbondanza show the technique at every level of quality. The Naples National Archaeological Museum holds many detached Pompeian wall paintings, where the secco layers can be examined at close range.

For Renaissance secco, the Sistine Chapel is the primary site, though the secco passages are difficult to distinguish from the buon fresco without technical analysis. The Arena Chapel in Padua shows where Giotto's secco additions have deteriorated, leaving the blues faded and the highlights missing. For Byzantine secco, the churches of Mistra in Greece and the monasteries of Mount Athos have significant examples. When you visit any of these sites, look for the areas where the paint has flaked to reveal bare plaster. Those are the secco passages, and their absence tells you exactly where the technique was used and why it matters. For more on the broader context, read our entries on buon fresco and tempera, or explore our post on how to read a painting.