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NARRATOR: Coming up, on 'Secrets of the Dead'... her smile has captured the world's imagination.
MAN: This woman smiling, looking at you, it's very intimate.
NARRATOR: But there is a second 'Mona Lisa' with that same enigmatic smile.
Did Leonardo da Vinci paint the most famous work of art twice?
Now art historians are using science to uncover the truth.
We found that the histograms for the two 'Mona Lisa's are virtually identical.
NARRATOR: 'The 'Mona Lisa' Mystery,' on 'Secrets of the Dead.'
NARRATOR: She is the most famous work of art in the world.
Her name synonymous with intrigue.
Her expression guards a secret 5 centuries old.
You see a face which is just about to smile.
It's almost a philosophical picture, and it's a demonstration of what painting can do.
NARRATOR: The 'Mona Lisa' wasn't always a celebrity.
She didn't steal the spotlight until she was stolen herself.
Vanished, hidden away for more than two years.
In her absence, a second 'Mona Lisa' appeared.
She looked younger and fresher.
But she was unfinished.
Had Leonardo da Vinci painted the world's most famous portrait twice?
Evidence suggests Leonardo worked on the 'Mona Lisa' at two different periods in his life more than a decade apart.
Is this missing link an early study for the legendary portrait?
Is it a copy from Leonardo's studio?
Or a most cunning forgery?
Now with recently unearthed archives and the latest science, experts set out to uncover the secrets behind her enigmatic smile... and finally solve the mystery of the 'Mona Lisa.'
August, 1911.
At the Louvre Museum in Paris, a small portrait, the 'Mona Lisa,' hangs in a Renaissance gallery.
Until now, she's been a work of little renown, but she's about to become a sensation.
After the museum locks its doors, a handyman, Vincenzo Peruggia, climbs out of hiding and pries the portrait from its frame.
He knows the layout of the gallery well.
He was recently hired to do renovation work at the Louvre.
Peruggia carefully wraps the priceless wooden panel in a cloth.
The next morning, in broad daylight, he walks out with the 'Mona Lisa' tucked under his arm.
An entire day passes before anyone notices the masterpiece is missing.
Then, she hits the headlines.
Until the heist, Leonardo da Vinci's portrait was known mainly to art experts.
Almost overnight, the 'Mona Lisa' became a household name.
The scandal had made her a superstar.
The police interrogate a number of suspects but fail to zero in on the handyman.
The 'Mona Lisa' had vanished.
No one knew if she would ever be seen again.
Around the time of her disappearance, an art dealer was traveling through England in search of rare objects.
He claimed that while visiting an estate in Somerset, someone made him an intriguing offer.
The only recorded detail is the name of the buyer-- Hugh Blaker.
The owner claimed a relative had returned from a grand tour of Italy, bringing a mysterious painting back with him.
It was a most remarkable portrait.
At first sight, it looked like the 'Mona Lisa,' but something about it was different.
She seemed more youthful, but it seemed to be the same woman as in the famous portrait.
She had been painted with a familiar perfection.
Could she have been created by Leonardo da Vinci himself?
In 1913, the 'Mona Lisa' once again made headlines when the now-famous portrait was returned to the Louvre.
The thief had hidden the painting for more than two years and was only caught while trying to sell it in Florence.
In England, the art dealer Hugh Blaker allegedly bought the portrait he was offered, the so-called 'Isleworth Mona Lisa.'
He wanted to know more about his mysterious acquisition.
Could there actually be two 'Mona Lisa's?
[Man speaking Italian] TRANSLATOR: On the basis of the knowledge we have to date, there are two theories.
According to the traditional theory, there is only one portrait in the Louvre.
The other suggests that there are two completely different paintings.
NARRATOR: Rumors of a second 'Mona Lisa' had just begun to circulate, sparked by newly discovered records describing a different version of the painting.
As an art dealer, Blaker was likely aware of the theory.
Could he now be the proud owner of this fabled other 'Mona Lisa'? The mystery of the 'Mona Lisa' begins in Italy, during the cultural explosion of the 15th and 16th centuries-- the Renaissance.
Leonardo, a central catalyst of the age, artist, inventor, engineer, was the definitive Renaissance man.
His every act was driven by an insatiable scientific curiosity.
MAN: Leonardo described himself once as a [speaking Italian], which can either be translated as a disciple of experience or as a disciple of experiment.
And throughout his life, Leonardo was a relentless, tough-minded experimenter.
It was, in a sense, his creed, his belief in the importance of questioning, of searching, of investigating and experimenting.
[Man speaking Italian] NARRATOR: He approached every challenge in technology or the arts with an unparalleled hunger for invention.
He wants the picture to be a total remaking of the natural world.
He wants everything to be in there.
He wants movement, he wants life, he wants objects, he wants anatomy, he wants geology, he wants botany, and in a sense, that's more even than a moving film could do these days.
So, in a way, it's an impossible agenda.
He's setting a standard for a picture which no one, not even Leonardo, could possibly meet.
NARRATOR: In 1503, the master took on a surprisingly simple commission.
Keeping up with the nobility in Florence, one of the richest city-states in Italy, was not always easy for Leonardo.
Leonardo's relationship with Florence was kind of a troubled relationship.
Florence was associated with a world which he might have wanted to join but felt excluded from, partly from his illegitimacy, partly for temperamental reasons.
So, he honed his craft and his skill here, but he never quite felt at home.
He's even described at one point as being impatient with the paintbrush.
He doesn't wish to pick up the paintbrush because he's pursuing so many other ideas.
NARRATOR: Ideas can be slow to fill the coffers, and for Leonardo, the paintbrush was a trusted source of revenue.
Leonardo's usual patrons were princes and high-ranking clerics, people in the public eye.
Now he was being asked to paint a portrait of a relative unknown-- a silk merchant's wife.
Clues to the curious commission can be found in the library of one of the most renowned art collections in the world-- the Uffizi Gallery in Florence.
The library holds the first edition of a seminal work on art from the Italian Renaissance-- 'Lives of the Most Excellent Italian Painters, Sculptors, and Architects,' by Giorgio Vasari.
Published in 1550, it's considered the preeminent source of information on Renaissance art.
Vasari wrote the manuscript after Leonardo's death, but with full access to the artist's records and eyewitnesses.
Vasari writes of a silk merchant named Francesco del Giocondo, whose sons confirmed that Leonardo da Vinci painted a portrait of their mother.
Her name--Lisa. Mona Lisa.
'Mona' is an archaic Italian word for 'lady.'
The author described the portrait in great detail.
The lashes demand the greatest delicacy of execution.
The eyebrows could not be more natural.
The mouth seemed in truth to be not colors, but flesh.
[Vezzosi speaking Italian] TRANSLATOR: In his description, the eyelashes are mentioned as an important characteristic.
He marks them out as an extraordinary feature of the painting.
NARRATOR: But is Vasari describing the picture now hanging in the Louvre behind bulletproof glass?
In this portrait, there is no trace of the eyelashes, lips, and eyebrows that so delighted the Renaissance writer.
[Vezzosi speaking Italian] TRANSLATOR: If we look at the 'Mona Lisa' in the Louvre, we can see that these eyelashes do not exist.
This raises doubts if Vasari was familiar with the painting in the Louvre or if there could be two different works.
NARRATOR: If Vasari was describing the painting in the Louvre, where are the lashes and brows?
New photo technology can peel back the layers of history hidden behind coats of paint.
French technician Pascal Cotte uses cutting-edge cameras to try to solve the mystery of the missing eyebrows.
A high-resolution sensor records a series of images at different wavelengths of light.
COTTE: I found the eyebrows with only 3 filters and only in the visible range.
We don't need the infrared range to find it, because this is very thin and this is very close to the surface of the painting.
There is no clear scientific answer how the eyebrows disappeared.
We can only make the supposition that someone cleaning the varnish on top of 'Mona Lisa' removed the eyebrows because the eyebrows were painted inside the varnish.
NARRATOR: What little remains doesn't seem to justify Vasari's effusive account.
It could be he had seen a different version of the 'Mona Lisa.'
Many legendary paintings have been transformed through a murky history of repairs and restoration.
I found myself going to many museums and studying, obviously, hundreds of works of art in museums environment, and the visitors don't realize that most of the times, they are looking at a surface that is far from being the original one.
The original one meaning how much has changed, how much material has been added, how much has decayed, and how much is what you see is the result of several restorations as well as several cleaning jobs.
NARRATOR: The restorer Ernst Lux has saved many masterpieces from decay.
He knows how the preservation techniques of past centuries could damage a work of art.
LUX: You have to imagine in those times how cleanings had been done.
There was a mixture normally of turpentine, alcohol, and ammonia.
Maybe added some lavender oil or whatever, or half onions, and all these substances have one thing in common-- they are extremely aggressive.
NARRATOR: So, this could still be the 'Mona Lisa' Vasari described-- the fine lashes and eyebrows scrubbed away by centuries of harsh restoration.
But Vasari's account emphasizes another quality of the portrait-- one that sets it apart from the 'Mona Lisa' in the Louvre.
It was unfinished.
Is it possible he was describing the Isleworth 'Mona Lisa,' the version Hugh Blaker bought in England?
Today, the Isleworth 'Mona Lisa' is kept in a secret location in Switzerland, locked away in an armored safe.
[Beeping] The portrait has changed hands several times since its discovery.
In 2008, it was acquired by a group of international investors.
The identity of the buyers and the price they paid for the painting is a closely guarded secret.
Another feature aligns with Vasari's description-- the background remains unfinished.
The landscape behind the figure is almost completely missing.
Even unfinished, it could still be Leonardo's work.
Its incomplete state would be typical of a busy artist of his caliber.
Leonardo's restless mind, his restless interest in the world around him, in new trains of thought, new areas of study, new paintings to undertake seems to make him a man who is always discarding and abandoning and moving on from paintings and leaving them unfinished.
NARRATOR: In 1503, Leonardo was awarded a major commission, the most prestigious assignment in Florence.
That same year, he began work on the 'Mona Lisa.'
Leonardo was chosen to commemorate a famous battle on the walls of the Palazzo Vecchio.
The Battle of Anghiari was a decisive moment in the city's history.
For the mural, he devised a new untested technique.
But for once, his ingenuity backfired.
The hot wax colors took too long to dry, failed to adhere, and began to drip down the walls.
It was the most ambitious assignment Florence had to offer.
And Leonardo had failed.
Halfway through the job, he threw in the towel, leaving the unfinished fresco behind.
There is nothing left of it today.
It was not the first time he had abandoned a commission.
Several of his most famous works remain incomplete.
I think Leonardo was the sort of artist who, in a sense, never thought pictures were finished.
He could always see additional possibilities.
He could always see something that seemed to him a bit better, so, he never settled in that way.
NARRATOR: It's possible Leonardo also lost interest halfway through painting Lisa, the wife of the silk merchant.
[Horse nickers] Comparing the portraits, the two women are clearly the same person, but in the unfinished version, she seems slightly younger.
Could this be a clue as to when she was painted?
Evidence regarding the timing recently came to light at the University of Heidelberg in Germany.
Conservators at the library stumbled across a handwritten note in the margin of a 16th-century book.
[Woman speaking German] TRANSLATOR: One early owner of this book was Agostino Vespucci.
He was personally acquainted with Leonardo.
We can assume that he had access to Leonardo's studio, that he'd seen his pictures, and after a visit, he made the handwritten note in his book.
He writes that Leonardo usually completes the main parts of his subjects and often leaves the rest of the painting unfinished.
He cites the portrait of Lisa del Giocondo as an example, and dates it October 1503.
NARRATOR: In October 1503, the portrait had not been finished.
[Man speaking Italian] NARRATOR: At that time, Lisa del Giocondo was a young woman of 24.
Her husband hired Leonardo to paint her portrait while she was expecting their second child.
[Speaking Italian] NARRATOR: Although she would one day be celebrated as Leonardo's most beguiling muse, it's likely she spent very little time with the master himself.
KEMP: The artist would have made a sketch.
They would have made a likeness of some sort.
And that probably was about the end of it.
The sitter wouldn't be there.
This idea of the sitter who sits in a chair, the artist sits there, and you sit there while he spends ages and ages making the portrait, that wouldn't happen at all.
NARRATOR: For Leonardo, the style of painting is a departure from the grand scale of his usual work-- imperious political portraits and somber religious scenes.
KEMP: She's a bourgeois Florentine lady.
and this is an intimate portrait.
It's not a great public portrait.
This woman smiling, looking at you, it's very intimate.
NICHOLL: We see a face which is just about to smile, and so the painting contains the future moment in which Lisa del Giocondo will break into that smile.
But she hasn't done quite yet.
Mona Lisa herself is a young woman just on the brink of changing, because she's now a mother, she's fleshing out, she's a beautiful, young woman who is going through physical and personal changes, because she is now a young mother, a young wife.
NARRATOR: A portrait by Leonardo would surely have been a major expense for the family, but no record of the commission exists.
The question of why continues to puzzle historians like Giuseppe Pallanti.
[Pallanti speaking Italian] TRANSLATOR: I've conducted extensive research in the archives in Florence, including the Archivio degli Innocenti.
But I have found no documentary evidence of a contract between Francesco del Giocondo and Leonardo.
NARRATOR: Florence's tax system required citizens to submit detailed records of all income and expenses.
Financial transactions and assets were meticulously archived, a rich resource for historians.
[Pallanti speaking Italian] TRANSLATOR: The document that all art historians have been looking for would prove that the portrait had been paid for, but unfortunately there is not a single piece of evidence to suggest that Francesco del Giocondo made any payment to Leonardo.
NARRATOR: From 1503 to 1506, when Leonardo lived in Florence, there is no record of the Giocondo family spending any money at all on a painting.
Perhaps they never received the finished portrait.
[Speaking Italian] TRANSLATOR: Why had Leonardo not delivered the painting?
There is no logical explanation.
It was in Leonardo's interest to hand over the painting and receive his fee, and Francesco would also have had an interest in owning a picture painted by the most famous painter of the age.
There is no rational reason why Leonardo should have painted the picture and then kept it for himself.
NARRATOR: It could be that the portrait wasn't finished and Leonardo never collected on his fee.
But then, what did he do with the painting?
If he kept it for himself, it must have stayed with him for a very long time, possibly for the rest of his life.
Leonardo spent his final years in France at the invitation of King Francis I.
He lived in a small chateau in the Loire Valley until 1517, when he died and was buried in the local chapel.
[Hoofbeats on road] Two years before his death, an important guest would leave a tantalizing clue.
[Horse whinnies, nickers] The visitor's name-- Cardinal Luigi d'Aragona.
He arrived with his private secretary--Antonio de Beatis.
De Beatis recounted the cardinal's visit in a detailed diary.
The aging Leonardo showed the cardinal several of his works.
[Men speaking Italian] NARRATOR: 'St. John the Baptist,' 'The Virgin and Child with St. Anne'... and a portrait de Beatis describes as a certain Florentine woman done from life.
Nearly 400 years later, in 1905, the diaries were published.
They set off a storm of speculation about Leonardo's most famous work.
The diaries state that the 'Mona Lisa' was commissioned by the late Giuliano de' Medici.
This contradicts accounts that Leonardo had been hired by Lisa's husband, the silk merchant Francesco del Giocondo.
[Speaking Italian] TRANSLATOR: The two documents by Vasari and de Beatis differ with regard to the dates and the context.
They provide no clear answer.
But it is clear that Francesco del Giocondo and Giuliano de' Medici cannot both be the client.
This supports the theory of two different portraits.
NARRATOR: For both accounts to be accurate, there would have to be two versions of the portrait: the finished masterpiece painted for Giuliano de' Medici and an unfinished version commissioned by Lisa's husband.
The tale of two 'Mona Lisas' quickly spread throughout the art world, to people like dealer Hugh Blaker, who just a few years later claimed to have discovered his Isleworth 'Mona Lisa.'
Had he perhaps not discovered it at all?
Could he have painted it himself or commissioned a talented forger to re-create the unfinished portrait?
KEMP: Leonardo is probably the most copied artist of his generation, and it goes through the 16th century.
They keep making versions and copies and so on and it clearly was a famous look.
You know, people liked pictures that said Leonardo to them.
NARRATOR: Hundreds of copies of the 'Mona Lisa' circulate throughout the world from different periods and of varying quality.
It's possible the Isleworth 'Mona Lisa' is one of them.
As a forgery, its genius would lie in its obvious departures from the version in the Louvre.
No one would suspect it was an attempted copy.
It would be seen as an additional 'Mona Lisa'... one that had never been finished, as the Renaissance writer Vasari described.
The timing of her discovery is also dubious.
The Isleworth 'Mona Lisa' appeared just after the original was looted from the Louvre, a time when a forger could be tempted to cash in on her absence.
So is the Isleworth 'Mona Lisa' simply a fake?
LUX: When I make an examination of a painting after the first view of the main side, I just turn it over and look at the back side because I can see a lot of information of the history of this painting on the back side, also.
You have all the dirt of the centuries.
You have the inscriptions. You have collector numbers.
You have, maybe, scenes, stamps, whatever.
So the back side is normally a much more unchanged part of the history of the painting than the front side.
NARRATOR: The back of the Isleworth remains hidden from scrutiny.
It was glued on top of a second canvas in the early 20th century.
For Ernst Lux, this alone is suspicious.
If you want to produce a forgery, this re-lining saves a lot of work because you don't have to imitate the back side of the painting with the dust, inscription, with the history.
In many cases, the faking of the back side is much more difficult than to fake the front side of the painting.
NARRATOR: Perhaps a brilliant counterfeiter had thought of nearly everything... but he could never have anticipated the technology to come.
At the Swiss Federal Institute of Technology in Zurich, experts used carbon-14 dating to authenticate ancient objects.
Since canvas is woven from plant fibers, a painting makes a perfect subject for the test.
The challenge lies in sampling only the painting itself, not an easy task when the canvas has been re-lined and glued to a second layer.
MAN: We need to take this sample only from the original canvas, which gives the right age.
If we mix it with the glue of the other canvas, we get wrong results, and it's very difficult to purify this material so that we extract and insulate the original fibers.
NARRATOR: Aside from being unfinished, the background of the Isleworth 'Mona Lisa' features another key difference from her counterpart.
In the Isleworth, she is flanked by two pillars, while in the Louvre 'Mona Lisa,' the bases of the columns can just barely be seen.
Why would a counterfeiter have added these columns?
Art historians had long assumed that the 'Mona Lisa' in the Louvre had been trimmed, 10 centimeters off of each side.
If this were true, the columns would have once been visible.
The theory seems to have been supported by an illustrious witness, the Renaissance painter Raphael.
Around 1504, the young talent had just moved to Florence and is said to have paid a visit to Leonardo's studio.
It was probably during the visit that he drew a highly informative sketch of one of Leonardo's works.
KEMP: There is a very nice pen-and-ink drawing of a woman sitting at--with a balcony with columns down the side, which clearly is a kind of revision of the 'Mona Lisa' on his own behalf.
NARRATOR: What the drawing doesn't reveal is whether the painting was finished.
KEMP: So there was obviously enough to see that the basic composition was there: the figure, the pose, even the columns and so on.
They were certainly known in Florence, and Raphael would have known that before 1507, 1508 when he left Florence.
NARRATOR: Which painting, which columns had Raphael seen?
The mystery persisted until 2004, when restorers at the Louvre removed the frame from the 'Mona Lisa' and discovered the painting had never been trimmed.
There were never any columns in the portrait.
The revelation means any version of the 'Mona Lisa' with visible columns is most likely a fake, based on a false idea.
But what of Raphael's drawing?
A comparison of his sketch with the Isleworth 'Mona Lisa' reveals that the columns are strikingly similar.
Does this mean Raphael had seen the Isleworth 'Mona Lisa' in Leonardo's studio, making it an early version of the famous portrait?
Or is it a later forgery, based on the now-debunked myth that at some stage the columns had been cut off?
Determining when she was painted proves more challenging than expected.
Her exact age eludes even the experts in Zurich.
SYNAL: In general, the time range between the end of the 15th century and the middle of the 17th century is a little bit difficult because the C-14 concentration in the atmosphere has changed a lot, and this makes it very difficult to get precise dates during this time range.
NARRATOR: The analysis reveals that the canvas of the Isleworth 'Mona Lisa' was probably manufactured between 1500 and 1650.
It could have been made during Leonardo's lifetime.
The results which we have now fit the characteristics of a canvas originating from the end of the 15th century or the beginning of the 16th century.
[Donkey breathing heavily] NARRATOR: The canvas fits the timeline, but did Leonardo's hand apply the paint?
NICHOLL: Beneath him, there is a hierarchy of assistants, pupils, and junior garzone, as they are called-- lads who are helping-- and each has their part.
NARRATOR: Leonardo's assistants were often skilled artists themselves.
He devised the concepts and rendered the main features of the painting, but for the background and tiresome details, he was happy to pass the paintbrush to an apprentice.
SERACINI: Obviously the style, the idea, the creativity of the subject, we tend to believe that was the main work of the master.
But the execution, per se, to think that only the master would paint, that's an illusion.
NARRATOR: The production of art in the Renaissance was based on division of labor.
A flourishing studio like Leonardo's would otherwise be unable to keep up with demand.
This also freed up time for Leonardo to get creative in other ways.
NICHOLL: The 'Mona Lisa' certainly bears witness, or contains the evidence of, Leonardo's experimentation with different techniques and with different actual physical paint and varnish and glazes as the years went by.
Of course, painters had their own recipes for making paint.
It wasn't just a question of going down to the shop and buying a series of bottles or tins of paint.
You mixed your own paints, using particular pigments, using particular bases, using particular mixes of oil and varnish and types of oil.
NARRATOR: Today, this artistic alchemy can reveal the signature of a painter.
To find it, researchers take microscopic samples of the pigment.
Will paint from the Isleworth 'Mona Lisa' expose her creator as a fraud?
The samples are cast in resin and examined under a microscope, revealing the structure of the painting, how the pigments were mixed and layered.
The key is to determine whether the paint's recipe is consistent with mixtures used during Leonardo's day.
Any pigments invented after his death would expose the portrait as a fake.
The tests reveal that no modern materials were used in the Isleworth.
It seems to have been created while Leonardo was alive.
PASCAL COTTE: NARRATOR: But was the portrait painted by the master himself, or if not by Leonardo, by someone very close to him?
One of his students nicknamed Salaí was more than just a pupil.
NICHOLL: Salaí was also, according to contemporary evidence, and certainly according to our own suppositions now, Leonardo's lover, Leonardo's confidant, friend, right-hand man, and bedmate.
Vasari says it in a rather roundabout way, but makes it pretty clear that Leonardo loves Salaí. NARRATOR: It's possible that Leonardo's young lover, himself a talented artist, began a copy of his mentor's 'Mona Lisa.'
NICHOLL: So, to say there are two--or more than two; there are several versions of the 'Mona Lisa'-- is not the same as saying Leonardo himself painted two entirely separate paintings-- one in 1503, the other much later.
My own view is that the other 'Mona Lisas'-- that is to say, the ones that aren't the one sitting in the Louvre-- are studio productions.
NARRATOR: If Salaí copied the 'Mona Lisa' in Leonardo's studio, it's possible he wasn't the only one.
At the Prado Museum in Madrid, another copy was recently found to show corrections to the head, shoulder, and fingers-- identical to corrections found on the version in the Louvre.
Someone had altered the copy at the same time as the original.
KEMP: The making of copies in studios or versions of pictures was very common.
If you look at the great artists of the time, most of them would have studios and smaller-scale pictures.
Things like Madonnas would be produced in some numbers, and the pupils would assist in that, and Leonardo wasn't different in that respect.
It was clearly a way of producing small-scale, Leonardo-brand pictures.
Leonardo himself also says you should have 3 types of picture.
You should have the top-quality ones, which we may think of as the 'Mona Lisa,' for instance; you would have the middle-quality ones, perhaps the 'Madonna of the Yarnwinder,' a small-scale Madonna produced by Leonardo in studio; and then you had other ones which were kind of OK, but these basically are studio products, so there's good evidence to think that Leonardo had grades of pictures.
NARRATOR: But is the evidence strong enough to say the Isleworth came from Leonardo's studio?
The canvas is the right age, the pigments are typical of those used during Leonardo's life, but one major difference calls the Isleworth into question.
All of Leonardo's known paintings-- 'The Virgin and Child with Saint Anne,' 'Saint John the Baptist,' 'The Virgin of the Rocks'-- they are all painted on wood, unlike the Isleworth.
Why would he make a canvas version of a painting on wood?
The Vatican Library holds a valuable collection of Leonardo's writing called the Codex Urbinas.
In his 'Treatise on Painting,' Leonardo devotes an entire chapter to techniques for working with canvas.
He clearly researched and possibly tried his hand at painting on canvas.
Could the Isleworth 'Mona Lisa' be the result of one of these experiments?
An X-ray of the painting offers a clue.
LUX: If you look at X-rays of paintings by Leonardo or his contemporaries, they all have a blurry appearance.
This is caused by the lead white in the preparation layer, and this lead white blocks the X-rays.
If you look at the X-ray of the Isleworth 'Mona Lisa,' you see a very clear image, and this shows that there is more or less no lead white in the preparation layer.
Leonardo and his contemporaries more or less always used lead white in the preparation.
NARRATOR: But perhaps not always.
In his 'Treatise,' he describes in detail how to prepare a canvas for painting, but never mentions the use of lead white.
The omission is peculiar, but perhaps not for a man always on the edge of innovation.
KEMP: What scientific examination is telling us about Leonardo's technique is it's very variable.
It's almost as if he tackles each picture on a new basis.
NARRATOR: When painting on wood, a base layer of lead white brightens and enhances the colors.
It's essential for achieving the 3-dimensional effect Leonardo realized with the 'Mona Lisa.'
But his mastery of mixing and applying the colors was an art form in itself.
KEMP: What we do see, though, is his ability to control oil glazes, these very thin layers of color, and to lay them on top of each other in a way which is not disastrous, because if you lay drying pigment on top of pigment that isn't dry, you get all sorts of trouble.
NARRATOR: Leonardo's technique relied on perfect preparation.
[Leonardo grumbling in Italian] NARRATOR: All pigments in his studio had to comply with his exacting standards.
Not every color made the cut.
Leonardo's distinct use of color could have left clues hidden in his work, an artistic signature that could accurately trace a painting to the master.
One man is convinced he can find it.
At the University of California in San Diego, research physicist John Asmus is one of the few people in the world to examine both 'Mona Lisas.'
He believes he can identify the hand of a genius by comparing the statistical characteristics of color and brightness.
ASMUS: When a forger does a copy or a copyist does a copy, something of that copyist's technique finds its way into the painting, and a casual observer says, 'These two paintings are the same.'
But if you look at the statistics and the numerical variations on those statistics, you always find differences, so we digitized both of the 'Mona Lisas' and we compared the statistics of the pixels-- their intensities, their standard deviation, their distributions-- and we thought that this would be a way of scientifically validating what connoisseurs see when they look at these two paintings.
NARRATOR: Analyzing the scans pixel by pixel, Asmus compares the flow of light and color, right down to the individual brush stroke.
Even he is stunned by the results.
And we found that the histograms for the two 'Mona Lisas' are virtually identical.
You could switch them in front of me, and I couldn't tell which was which.
If you look at the statistics of this, I would say that it's 99% certain that the two 'Mona Lisas' were done by the same artist.
NARRATOR: If the results are correct, why would Leonardo da Vinci have painted the same subject twice?
The answer might be found in Rome, where, late in life, Leonardo perfected his technique.
NICHOLL: We don't really fully know what he was experimenting on in the Belvedere in Rome, but it seems to have been some idea of, as he put it in one note, 'capturing sunlight,' and has probably contributed much to his rather dubious reputation in Rome as something approaching a sort of magician or a shaman.
NARRATOR: Many experts believe Leonardo's superb handling of light, color, and shadow reached the peak of perfection in his final work, a picture of Saint John the Baptist.
It was most likely commissioned by Pope Leo X.
Leonardo's companion Salaí is thought to have served as the model for the saint.
Today, the picture hangs in the Louvre, alongside two other works: 'The Virgin and Child with Saint Anne,' from the same period, and the 'Mona Lisa.'
In all 3, he used his famous sfumato technique to mimic how the human eye perceives subtle changes in color and light.
NICHOLL: Leonardo in Rome was experimenting with finer and finer glazes and varnishes, which he used to layer again and again over the paint surface, creating that sort of shimmering, mirage-like quality.
And Leonardo, particularly in Rome, in his later years in Rome, was working almost like an alchemist on the preparation of these very subtle oils and varnishes.
And indeed, the Pope, Leo X, the Medici pope who was there in Rome at the same time and who had rather a jaundiced or skeptical view of Leonardo, complained about the fact that he was always at work on his sort of chemical pots and pans, producing these varnishes, when he should be getting on with the painting.
Well, of course, Leonardo would perhaps have replied, 'I am getting on with the painting because this is an essential part of the operation.'
NARRATOR: Was the 'Mona Lisa' also painted in this late period of artistic refinement?
In the 'Mona Lisa,' when he comes to do that, everything is working.
You know, it's-- everything works: the veils, the transparency, the opaque pigments.
He's got it all under control, so this, begun probably in 1503, is a point of complete mastery after all the experimentation.
PASCAL COTTE: NARRATOR: The 'Mona Lisa' from the Louvre consists of up to 30 super-fine films of paint with so many layers, the naked eye can no longer see individual brush strokes.
Is it possible Leonardo wanted to try his new technique on an old work he had abandoned long ago?
Perhaps he saw the original as a failed experiment on canvas.
Now he could re-create the alluring Florentine woman in all her magnificence, using his recent artistic advances.
The similarities between the two portraits even go beyond the obvious.
Though the size of the Isleworth is larger, the framing wider, when the scale is adjusted, the figures are exactly the same size, with identical proportions.
The biggest difference between the two paintings is, in fact, not their appearance, but their condition.
In contrast to her look-alike in the Louvre, the passage of time has left little trace on the Isleworth 'Mona Lisa.'
LUX: The unusual thing, looking at this painting, is the nearly perfect condition.
You only have some tiny losses, minor retouches, no damages of the painting surface.
On all pieces of art I have worked on as a restorer, or I have done researches, they're looking completely different, much more damaged because of the time.
So my impression is that this painting is-- couldn't be 500 years old.
NARRATOR: It seems unfathomable that the Isleworth 'Mona Lisa' could have been stored under perfect conditions for 500 years... remaining completely unknown to the world until an art dealer stumbled across it just when the Louvre 'Mona Lisa' went missing.
LUX: So it needs a lot of explanation to bring this... painting into the direction of being a Leonardo.
The easy explanation, I think, is that it's not done by Leonardo.
NARRATOR: Others say if Leonardo painted one, he painted them both.
ASMUS: The weight of the evidence is that it had to be done by the same artist with the same hand, using the same technique.
NARRATOR: Some believe the 'Mona Lisa' mystery has been solved.
For others, there is still not enough evidence to say for certain.
Even with the most sophisticated science, it's not easy to outwit a genius, whether prankster or prodigy.
'Mona Lisa' may never divulge her secrets.
SERACINI: There is no way today that-- no exam, no sets of exams, no single scientist, no group of scientists that today will be able to identify the artist who made any work of art, including Leonardo.
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