Technique & restoration
Leonardo da Vinci's frescoes: technique, fragility and conservation
Why did The Last Supper deteriorate almost immediately? What remains of the Battle of Anghiari and the Sala delle Asse?
The essential point
Leonardo is not a traditional fresco artist
His murals are often called "frescoes" for convenience. Yet, The Last Supper is not executed using the true fresco technique, on wet coating. Leonardo wants to work slowly, take up the details and superimpose effects comparable to those of a painting on wood. This choice produces an extraordinary - and extremely vulnerable - painting.
The Last Supper
Dry painting on a white preparation, completed around 1498 and already altered a few years later.
Battle of Anghiari
Florentine monumental decor never completed, today lost and known through copies and drawings.
Sala delle Asse
Plant decor designed for the Sforza castle, covered, rediscovered and still studied in restoration.
Real fresco
Paint while the wall dries
A first layer of coating prepares and regularizes the masonry.
The thin layer is laid only on the surface that the artist can paint during the day.
Colors diluted in water penetrate the still damp coating.
As it dries, lime fixes the pigment in the wall rather than on its surface.
Milan · 1494 -1498
The Last Supper: paint a wall like a panel
According to the Museo del Cenacolo Vinciano, Leonardo places his pigments on a white preparation intended to smooth the wall. The colors therefore remain superimposed on the coating instead of being absorbed into it.
It uses a fatty tempera, particularly linked to the egg, in order to obtain intense tones, delicate passages and lighting effects impossible to treat with the same slowness in the fresh coating.
This method allows him to modify several zones simultaneously. She corresponds perfectly to his painterly temperament, but very poorly to the physical constraints of a damp wall.
Why the work suffers
A fragility inscribed in matter
Low adhesion
The colored layer rests on the preparation: it can flake when the support moves or humidity passes through the wall.
Humidity
The refectory is experiencing difficult conditions. Water carries salts, promotes lifting and modifies the balance of the support.
Old restorations
For centuries, filling in gaps often means repainting. These additions mask the original and introduce new materials.
Documented degradation
The Last Supper begins to disappear very early
The decor is generally considered finished.
Antonio de Beatis already reports that the paint is starting to deteriorate.
Vasari describes it as a blurred stain.
Repainted, transfer attempts and successive interventions modify its appearance.
The refectory is hit by bombings; the protected wall survives.
Pinin Brambilla Barcilon runs the large modern restaurant.
Modern restoration
Preserve without reinventing
The campaign carried out from 1977 to 1999 sought to find as much as possible the original areas hidden under the repaintings. Restorers consolidate the scales, remove additions compatible with this intervention and reintegrate the gaps with caution.
The result does not claim to reconstruct the brilliance of 1498. The current image preserves the losses and makes readable what really remains of Leonardo's hand.
Preventive conservation extends this work: air control, visitor limitation, set access time and continuous microclimate monitoring.
Florence · 1503 -1506
The Battle of Anghiari: The Lost Experience
The Florentine Republic orders Leonardo to produce a huge military episode for the Grand Council Hall of Palazzo Vecchio. Michelangelo must work on the opposite wall with the Battle of Cascina.
Leonardo prepared numerous drawings and began implementation, but abandoned the site. Later accounts evoke an experimental technique and poorly controlled drying; the exact details remain debated.
The work is then covered or destroyed during transformations of the room. We must distinguish the attested project, the old copies and the modern hypotheses on possible hidden fragments.
Sforza Castle
La Sala delle Asse: a painted forest to rebuild
A court program
Sixteen mulberry trunks rise towards the vault, where branches, foliage and ropes create a vast plant cradle. The mulberry tree refers to Ludovic "le More" and the silk economy.
A covered work
Changes in the use of the castle, layers of lime and old restorations have long masked or reinterpreted the decoration.
A construction site still active
Since 2013, analyses, cleanings and clearances have revealed new traces of the preparatory drawing and a project covering the walls more than previously thought.
Comparison
Three murals, three destinies
| Work | Location | Technical/state | Main problem | What we keep |
|---|---|---|---|---|
| The Last Supper | Santa Maria delle Grazie, Milan | Dry paint on preparation | Peeling, humidity, repainted | Consolidated original fragments and legible gaps |
| Battle of Anghiari | Palazzo Vecchio, Florence | Experimental wall project, unfinished | Abandonment then disappearance | Drawings, copies and sources |
| Sala delle Asse | Castello Sforzesco, Milan | Wall decoration with workshop | Invasive coverings and restorations | Vault, Monochrome and new preparatory traces |
Read a restoration
Original, gap, retouching: three levels to distinguish
Original material
Pigment and preparation that can reasonably be attributed to Leonardo's campaign and his workshop.
Gap
Area where the material has disappeared. Modern restoration generally avoids transforming it into a false original.
Reintegration
Limited intervention intended to reduce visual disruption, while remaining identifiable by close examination or documents.
Extend your gaze
Works by Leonardo in the store
Saint John the Baptist
Light transitions impossible to improvise in fresh coating.
See the collectionFAQs
Frequently asked questions
Is the Last Supper a real fresco?
No. Leonardo paints dry on a white preparation, with a technique allowing him to work slowly and pick up the details.
Why is The Last Supper so fragile?
Pigments are not integrated into the fresh coating. Humidity, salts, support movements and old restorations accelerated losses.
What remains of the Battle of Anghiari?
The original mural is considered lost. The project is known from Leonardo's drawings, descriptions and several old copies.
Is La Sala delle Asse entirely Leonardo's?
Léonard designs the decor and intervenes in its execution, but a project of this magnitude involves his workshop. Restaurateurs study the different hands and campaigns precisely.
Can we restore The Last Supper to its 1498 state?
No. Much of the original material has disappeared. Conservation seeks to stabilize and make readable what remains, not to arbitrarily recreate the new work.
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