How a chemist detects forged paintings experts miss

HostMost of us have been to a museum and felt that pull when we look at a famous painting. You can almost feel the history coming off the canvas, but it's wild to think that some of the world's most famous art might actually be a fake.

HostHow's it that a person who has studied art for thirty years can be tricked by a copy, but a lab test catches it every single time?

GuestIt comes down to what you're actually looking at. An art expert is trained to look at the soul of the work. They look at the way the brush moves, the way the light hits the paint, and the small habits a painter has that make them unique. Forgers are brilliant at copying those things. They spend years learning how to move their hand just like a master from the sixteen hundreds. They can mimic the feeling of a painting so well that even the best eyes in the world get a sense that it's the real thing. But a chemist doesn't care about the feeling. They're looking at the atoms. They're looking at what the paint is actually made of on a level that no human can see or fake.

HostSo, even if the painting looks perfect to our eyes, it's basically a different thing deep down?

GuestExactly. Think about the white paint they used back then. For hundreds of years, painters used lead white. It was made by putting lead and vinegar in a pot and letting it sit. Now, lead has a certain kind of clock inside it. Deep in the lead, there are these things called isotopes—which are just different versions of the same atom. Some of those versions are unstable. They break down over time at a very steady rate. When a chemist looks at a tiny speck of white paint under a machine, they're counting those atoms. If a painting is supposed to be three hundred years old, but the lead atoms inside it look like they were dug out of the ground ten years ago, the chemist knows the truth instantly. The forger can copy the brush strokes, but they can't make new lead look old to a machine.

HostBut could a forger just go find some old lead? Like, rip a pipe out of an old house from that time and use it to make their own paint?

GuestYou would think so, but there's a catch. When you melt lead down to turn it into paint, you basically hit a reset button on certain parts of that atomic clock. There's a specific metal called polonium that gets separated from the lead when it's heated up. Once that happens, the clock starts fresh. So, even if the lead itself is ancient, the moment the forger turns it into paint, they're leaving a timestamp that a lab can find. A chemist isn't just looking at the age of the lead, they're looking at how much it has broken down since the day it was actually made into paint.

HostThat sounds like a lot of work just to catch a fake. Is the lead test usually enough to prove a painting is a lie?

GuestIt's one of the big ones, but chemicals are everywhere in a painting. Another huge giveaway is the colors. For a long time, if you wanted a certain blue or yellow, you had to find very specific rocks or plants and grind them up. It was hard and expensive. But in the last hundred years or so, we started making brand new colors in labs that never existed before. One of the most common ones is titanium white. It's in almost everything now, from house paint to the stuff you buy at the art store. But it wasn't used in art until about nineteen twenty. If a chemist finds even a tiny bit of titanium white in a painting that's supposed to have been painted in the year sixteen fifty, it's game over. It's like finding a digital watch in a movie about the Middle Ages. The forger might have been careful, but maybe they used a modern brush that had a tiny bit of new paint on it, or they bought a canvas that was already primed with modern white.

HostIt feels like the chemist is looking for mistakes that have nothing to do with the art itself.

GuestThat's why they're so hard to beat. The art expert is part of a conversation with the painter. They're looking for the story. The forger is part of that same conversation. They're trying to talk back. But the chemist is just looking at the facts of the world. They're looking at the binding oil, too. Old oil paint dries in a very specific way. It takes decades, even centuries, for the molecules in the oil to link up and become a hard, solid mass. A forger can try to speed that up by baking the painting in an oven to make it look cracked and old, but that heat changes the chemicals in a way that looks totally different from natural aging. To a machine, a baked painting looks like a piece of toast, not a piece of history.

HostSo why do we even need the experts? If the lab is this good, why not just test every painting and be done with it?

GuestBecause the lab only tells you what the painting is made of, not if it's good or why it matters. A chemist can tell you a painting was made in sixteen forty, but they can't tell you if it was the master who painted it or just one of his students using the same lead. You still need the expert to tell you about the heart of the work. The chemistry is just there to keep everyone honest. It's the one thing a forger can never bribe or trick.

GuestA forger can mimic the hand of a master, but they can't mimic the way atoms break down in the dark.

HostThe painting on the museum wall might look like a ghost from the past, but the atoms inside are the only ones telling the truth about when it was born.