Hank: Art is a big business with people willing to spend thousands or millions of dollars on paintings by famous artists. They don't always get what they pay for though. Instead of a genuine Rembrandt, there's a chance that the new piece in their collection is a forgery.

Forgeries can be copies of existing paintings, or new works that mimic the style of the famous painter. So how do our experts find the fakes?

We have three main lines of evidence: You can check the artist's unique style and brush work, or look for records that show how the painting has changed hands over the years. But you could also bust forgeries with science.

Scientific examination using things like microscopes, X-rays and chemical analysis can reveal even more than what expertly trained eyes can see. Let's start at the surface, though.

All paintings naturally develop networks of cracks, called "craquelure", over time. These patterns reveal clues to the paintings' origin and history. Oil paintings are made of colored pigments, oil and a solvent that makes the painting more fluid, but evaporates off Meanwhile, the oil hardens into a solid layer, binding the colors together.

But time takes it's toll on paintings, and this solid layer starts to crack, thanks to changes in temperature and humidity, or just people handling the artwork. A craquelure's patterns depends on the chemistry of the paint, and how the artwork was treated over time.

To fake craquelure, some forgers use solvent washes and gentle heat to make their paint dry faster and crack right away. This artificial aging is more chaotic than the cracking patterns of real old art, but it can be hard to tell with the. Light microscopy, better image recognition software, and a good understanding of craquelure, can help "crack the case" on forgeries, or speed up authentication. If the cracks are missing, don't fit typical patterns, or are straight-up painted on, the art might be a forgery.

Now paintings may look flat but, there's usually a lot going on under the surface. Using infrared light and x-rays, scientists can look at deeper layers of a painting generally called the underpainting. That way they can look to c into the artist's mind, or rather their changes of mind. Some artists use a pencil or charcoal underdrawing to plan out a piece, but then do something different when they actually paint, maybe tweaking the subject's hands or changing the piece altogether.

Infrared light can penetrate through paint layers to reach the canvas and detect an underdrawing. Pale areas like canvas reflect infrared, whereas black areas like charcoal absorb it. So if an art examiner expect to find an underdrawing and it's missing, you may have a forgery on your hands.

But these techniques have confirmed genuine paintings to. Still Life with Meadow Flowers and Roses was loosely attributed to Vincent Van Gogh, but art historians weren't convinced. Tthe piece was unusually large for a Van Gogh, the signature was in a weird place, and he didn't normally paint so many flowers at once. In 2012, scientists used x-ray fluorescence to analyze the underpainting. High-energy x-rays can penetrate through the paint layers and knock electrons off atoms in the paint. As other electrons in the atom drop in energy levels to fill the vacancy, they admit their own x-rays at specific wavelengths which vary from element to element. With x-ray fluorescence, brushstroke patterns from different kinds of paints can be revealed beneath the surface of a painting. And beneath those pretty flowers was an entirely different scene: two topless men sparring.

This lineup with a letter Van Gogh wrote to his brother "this week I painted a large thing with two new torsos, two wrestlers" a painting that was never found until that moment. Because Van Gogh was also known for going over old canvases, this unusual still life seemed a lot more genuine.

Some of the materials that go into making paintings, the pigments and canvas, are also prime targets for scientists. Paints are mixtures of chemicals, and what chemicals were used changed over time, including which organic or synthetic pigments were used. Bbecause different artists used two different kinds of paints, you can see if the artwork is a good match by doing chemical analysis.

For instance, the molecular components of paint can be broken up into smaller components and separated by mass and analyzed using a technique called mass spectrometry. Mass spectrometry can also be used to detect differences and individual atoms like the different forms of carbon, the heavier radioactive carbon 14, and the regular carbon-12. Examining the ratio of those atoms and paintings can let scientists carbon date them.

All the nuclear testing in the late nineteen fifties caused a huge increase in carbon-14 levels worldwide, something we call the bomb peak effect. Carbon-14 was incorporated into all living things and putting the cotton plants that would be turned into canvases. And this was how forged painting attributed to the french artist Fernand Léger was confirmed fake.

Scientists extracted a microscopic, unpainted fragment of canvas, used a high-sensitivity technique called accelerated mass spectrometry, and clearly found some carbon-14. Specifically, the canvas dated to 1959, after Léger's death in 1955, so it could not have been his work.

With all these technologies at our disposal, science is really important when it comes to studying art, and scientists can work with historians to spot even the most careful forgeries.

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