Hidden Layers Beneath the Mona Lisa Reveal Leonardo's Process

For centuries, the Mona Lisa has captivated viewers with her enigmatic smile. But what you see on the surface is just the final chapter of a much longer creative story. Advanced imaging technology has revealed that Leonardo da Vinci didn't simply paint the portrait once—he continuously revised and evolved it, leaving multiple layers hidden beneath the visible masterpiece.

What the X-Rays Revealed

Using X-ray fluorescence spectroscopy and multispectral imaging, scientists discovered that the Mona Lisa contains numerous layers of paint showing significant changes. These aren't just minor touch-ups—the imaging reveals alterations to the subject's pose, features, and positioning. Leonardo experimented extensively, modifying the portrait as his vision evolved over the estimated 14 years he worked on it.

French scientist Pascal Cotte spent over a decade analyzing the painting using his Layer Amplification Method, claiming to have found evidence of three different portraits beneath the surface. However, this sensational claim has been heavily disputed by leading Leonardo experts.

The Expert Consensus

Martin Kemp, Emeritus Professor of the History of Art at Oxford and one of the world's foremost Leonardo scholars, offered a more measured interpretation. He explained that while the imaging is "ingenious in showing what Leonardo may have been thinking about," the idea of distinct, separate portraits "hiding underneath the surface is untenable."

Instead, Kemp describes what we see as "a continuous process of evolution"—the natural result of Leonardo's perfectionist tendencies and experimental approach. This wasn't three different paintings stacked on top of each other, but rather one painting that evolved dramatically over time.

A Window Into Genius

What the imaging does definitively reveal is Leonardo's revolutionary painting technique. Scientists found:

• Ultra-thin glaze layers, some just a few micrometers thick in light areas
• The rare compound plumbonacrite in the ground layer, confirming Leonardo used lead oxide to help dry his paint
• Evidence of a previously unknown preparatory sketch using the spolvero technique
• Total paint thickness never exceeding 80 micrometers—about the width of a human hair

This meticulous layering is what gives the Mona Lisa its luminous, lifelike quality. Each transparent glaze builds upon the last, creating depth and softness impossible to achieve with direct painting.

The discovery of the preparatory sketch raises a tantalizing possibility: somewhere in the world, there might exist a paper drawing by Leonardo's hand showing an earlier version of the Mona Lisa with a slightly different pose. For art historians, that would be an invaluable find.

The Takeaway

While headlines about "three hidden portraits" make for exciting reading, the truth is more nuanced and, arguably, more fascinating. The Mona Lisa wasn't painted once—it was painted dozens, perhaps hundreds of times, as Leonardo obsessively refined his vision over more than a decade.

What lies beneath the surface isn't a mystery woman or secret portrait. It's something far more revealing: a record of one of history's greatest minds at work, constantly questioning, revising, and perfecting until his dying day.