Hidden Techniques Behind Masterpieces of Leonardo da Vinci and Rafael Uncovered

A recent scientific study has revealed long-lost drawing techniques used by iconic Renaissance artists Leonardo da Vinci and Rafael, offering a rare window into how they developed their ideas before bringing them to life on canvas.

Researchers used modern imaging and chemical analysis tools to examine six historic sketches, uncovering the artists’ use of layered materials such as red chalk, metalpoint, and traditional ink. This approach sheds new light on the early stages of artistic creation during the Renaissance — a time when careful preparation on paper played a vital role in final compositions.

The study, led by Silvia A. Centeno from The Metropolitan Museum of Art, analyzed four drawings by Rafael, one by Leonardo da Vinci, and another by Perugino. These works were previously studied only through visual examination. However, new technologies now allow scientists to go beneath the surface without damaging the original pieces.

Early sketching methods brought to light

Advanced tools such as X-ray imaging and light-based spectroscopy helped researchers track the artists’ process, showing how different materials were layered to create depth, detail, and tone. In one of Leonardo’s works, Virgin Adoring the Christ Child, researchers found the artist prepared the paper with a soft pink base made from a mix of red lead and bone ash. This base not only added texture but also gave warmth to the sketch.

Rafael’s drawings, including Madonna and Child and Studies of the Christ Child, demonstrated his skilled use of red chalk. The chalk was found to contain iron-rich ochre, giving it natural color variation. Rafael carefully controlled his hand pressure to adjust the shading, creating subtle lines and lifelike features.

In another example, Rafael’s Nude Male began with a light sketch using lead metalpoint, followed by stronger lines in iron gall ink. This step-by-step method allowed the artist to test his ideas before committing to permanent strokes.

Leonardo, too, used metalpoint techniques, selecting a blend of silver and mercury to form his base sketch. Later, he refined these outlines using the same type of ink. Scientists confirmed these layers through detailed chemical mapping.

Iron gall ink reveals artist’s final touches

The team also discovered widespread use of iron gall ink, a standard material of the time made from iron salts and tannins extracted from plants. Though this ink has faded from black to brown over the centuries, it remains visible thanks to the advanced analysis. In most cases, the ink was applied over lighter sketches, acting as a final outline or key detail.

Perugino’s Study of a Kneeling Youth also revealed similar use of metalpoint applied over a base of white bone ash. His materials included a silver and mercury mixture — a blend that had been difficult to detect until now.

These findings, published in the journal npj Heritage Science, offer a clearer understanding of how Renaissance masters thought through their compositions. According to Centeno, the research shows that these drawings were not just practice works, but crucial parts of the creative process.

By breaking down each step of the artists’ techniques, researchers have opened the door to appreciating these centuries-old drawings in a new light — not only as beautiful works of art, but also as carefully constructed plans for the masterpieces that followed.