IRA FLATOW, host:
You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow.
Museum goers look at paintings from many different angles. You know, you find yourself taking in all those different aspects - the color or the composition, the brush strokes. But there is something else many times, something that you cannot see - at least without some help. Many artists like Van Gogh and Wyeth, for example, recycled canvases by painting - actually painting over their earlier works. And while regular x-rays can detect the outline, there's still lots of details that are a mystery to art historians.
Well, museum chemists from Winterthur Museum have figured out how to fill in the details. They have adopted a new x-ray technology called confocal x-ray fluorescence microscope. That's what it is. And they can detect chemicals used in the different pigments in the paint. And using this technique to determine the colors, they have been able to digitally reproduce one of the NC Wyeth's most famous works. Their findings were published in the American Chemical Society journal this week.
And here to talk about it is my guest, Jennifer Mass. Dr. Mass is the senior scientist at the Scientific Research Analysis Laboratory at the Winterthur Museum, and she is an adjunct professor of art conservation at the University of Delaware.
Thanks for joining us today.
Dr. JENNIFER MASS (Senior Scientist, Scientific Research Analysis Laboratory, Winterthur Museum): Hi, Ira. It's great to be here.
FLATOW: Tell us what the painting was.
Dr. MASS: Okay. Well, the painting on the surface was a family portrait that NC Wyeth had made between 1922 and 1924. And it was actually a study for a larger mural that he was going to transfer onto his living room wall.
FLATOW: And has it been known for years that there's something underneath it?
Dr. MASS: It had been suspected. Actually, the painting had been x-rayed in 1997 by paintings conservators here at the Winterthur Museum and the University of Delaware. And so when they did a conventional x-ray, what they saw underneath was a black-and-white image of two men engaged in a fistfight, a very dynamic image. And when they worked with curators at the Brandywine River Museum, who owns the painting, they were able to identify it as a 1919 illustration that NC Wyeth had done for a magazine called Everybody's Magazine that was thought to have been lost since the 1920s, but, in fact, it wasn't lost at all. It was just buried beneath this family portrait.
FLATOW: Wow. So with the techniques that had been used, you could tell something was there and you could see what it was, but you couldn't bring out any of the colors or any of the depth of the painting.
Dr. MASS: Exactly. When you do conventional x-radiography, you get a black-and-white image of the buried painting. And it's really only a partial image, because you're imaging the positions of the piatomic number of pigments, like the lead of mercury-based pigments, because they absorb x-rays so strongly in the same way as when you go to the dentist and you wear a lead apron. The lead apron absorbs the x-rays strongly.
FLATOW: So you tried a different x-ray technique on the paint.
Dr. MASS: Exactly. We were using a technique called confocal x-ray fluorescence.
FLATOW: Mm-hmm. And what did that do for you?
Dr. MASS: Well, the way that the technique works is that we're going to be using a very high intensity x-ray beam. And so this is going to be an x-ray beam generated by a synchrotron. A synchrotron is a type of particle accelerator, and it allows you to produce an x-ray beam up to a million times more intense than the one you would experience at your dentist's office. And we did this at Cornell University at the high energy synchrotron source there.
FLATOW: Mm-hmm. And what does this allow you to do? To bring out the different colors that might be present that you couldn't see in conventional x-ray?
Dr. MASS: Well, this allows us to get a very tightly focused x-ray beam, an x-ray beam that's only 20 microns wide. And that's' about the size of a human hair. And so that lets us be very selective about the spot on the painting that we're analyzing. So, basically, what we're doing is we're shining this incredibly tiny x-ray beam on the painting. And at this point, we're doing what's known as regular or conventional x-ray fluorescence, which is something that museum scientists do in their laboratories all the time.
And what this means is that when this tiny x-ray beam hits the painting, all of the atoms in the paint layers that are hit by this tiny x-ray beam are going to emit or fluoresce their own x-rays. And so every type of atom fluoresces x-rays of characteristic energy. And so, for example, for chromium, which we see in green pigments, and cadmium that we see in yellow pigments, they're going to emit x-rays at different energies, allowing us to distinguish them from each other.
FLATOW: Mm-hmm. So then, do you run the x-ray machine over the whole painting?
Dr. MASS: We do, actually. And essentially, at this point, what we've done with the conventional x-ray florescence, as we scan it over the surface of the painting, what we're doing is collecting x-rays from the buried painting simultaneously with the painting on the surface. And so that makes it very difficult to determine which pigments belong to the surface painting versus which pigments belong to the buried painting.
And so then we have to add in the confocal technique. And what's different about the confocal technique is that we have an additional x-ray focusing device on the x-ray detector so that we're only collecting x-rays at a single focal point. We can move this focal point through the paint layers, and that allows us to determine the pigment composition of the surface painting and the buried painting sequentially. Or to put it in other way, it allows us to isolate the pigments that are in the buried painting.
FLATOW: So you can find different layers of pigments…
Dr. MASS: Exactly.
FLATOW: …one on top of the other, like a sandwich.
Dr. MASS: Exactly. And we can actually move our tiny focal point horizontally and vertically across the painting, as well, to generate a three-dimensional image of the paint layers.
FLATOW: And so that shows up on your computer screen some place as a new painting.
Dr. MASS: Exactly. Well, what we wind up getting is a three-dimensional map of the elemental composition of the paint layers. And then we can use this map in order to generate a full-color image of the buried painting. And so, for example, whenever we see titanium, we know that's a white pigment. And when we see cobalt, we know that that's a blue pigment. And so we can essentially play paint-by-numbers with our elemental data and turn it into a reproduction of the colors of the buried painting.
FLATOW: Wow. And so you were able to reproduce this whole painting underneath there.
Dr. MASS: Yes, it's true. We were able to reproduce the whole painting in color with the conventional x-ray florescence - the confocal x-ray florescence and some other micro analytical techniques in conjunction with our historical research, as well.
FLATOW: Have you got other paintings in store for this?
Dr. MASS: Absolutely. At the moment, we're focused on an illuminated manuscript, but we have some other paintings in discussion, as well.
FLATOW: Why would Wyeth would want to paint over his old paintings?
Dr. MASS: Oh, that's a great question. In fact, throughout history, artists have very commonly reused their paintings. And often, they were doing this strictly for a financial reason. Canvas was expensive. So they could save money by painting over one of their older paintings. But we actually know that this is not the case with NC Wyeth because of interviews with his son, Andrew Wyeth. And Andrew Wyeth told us that his father used to instruct him to turn his paintings upside down and then paint over them so that he could be inspired by the abstract shapes of the former composition as he made the new composition.
FLATOW: That's fascinating. How expensive is it to do this? I mean, can people around the world get use of this special kind of x-ray machine and do it themselves, without costing a whole lot?
Dr. MASS: Yes. This is actually becoming more and more common for art historians and art conservators to go to these research facilities, these synchrotrons, and typically at universities like Cornell University or Stanford University in the United States. But in Europe, it's actually fairly common for our conservators and our historians, to do this type of work with universities.
FLATOW: Yeah. And now you are a chemist, correct?
Dr. MASS: Yes, that's true.
FLATOW: And you specialize in chemistry - artist restoration?
Dr. MASS: Exactly, yes.
FLATOW: How many paintings have hidden stuff underneath them?
Dr. MASS: Well, art conservators who spend a lot of their jobs x-raying paintings have estimated that approximately 20 percent of paintings actually have buried images underneath. And for over a 100 years, people have been x-raying these paintings to try and get information about the buried images. And so what we've done really represents a step forward in being able to get information about the buried images in color.
FLATOW: Mm-hmm. So what's on - what painting's the next on your agenda? Have you got a favorite artist you'd like to go digging for, so to speak?
(Soundbite of laughter)
Dr. MASS: Well, we're in discussions about a Caravaggio, and so that's something of great interest to us. The Brandywine River Museum has told us that they have something like 30 to 40 Wyeths that have paintings underneath. And so that's certainly job security for us.
(Soundbite of laughter)
FLATOW: Well, how do you reproduce them? You want to show them, right? Do you then have - do you just print them out on a laser printer or something?
Dr. MASS: Actually, what we've been doing is using Photoshop. And so we take the plain old X radiograph, the black-and-white image, and then we're literally taking our elemental data in order to color in the black-and-white image in Photoshop to digitally reproduce the buried painting in color.
FLATOW: Mm-hmm. What does this tell you about Wyeth's art in general?
Dr. MASS: Well, it's really interesting in terms of what we understand about how he was working as an illustrator and how he felt about his work as an illustrator versus his work as a fine artist.
Throughout most of his career, he actually made the majority of his money working as an illustrator, and he was much beloved and prolific. He illustrated probably 112 books in his career, and is most well-known for his illustrations of Robert Louis Stevenson's "Treasure Island." And so although he has done all of these incredible illustrations, he really wanted to be considered as an artist rather than an illustrator. And so it has been thought that maybe a lot of his illustrations are actually buried under his paintings because he wanted to showcase his work as an artist rather than as an illustrator.
So that's one thing that we get about N.C., by doing this type of work. And the other thing that we get out of N.C.'s working methods by doing this type of work is that we can understand how he was working in making his paintings, knowing that they were going to be reproduced by a four-color photographic process as colored illustrations.
And so, for example, we see cadmium yellow being used throughout the buried image, because he knew that the painting was going to be reproduced using red, yellow, blue and black pigments, potentially as a color illustration.
FLATOW: Can you tell how his technique might have changed between these two different periods of painting?
Dr. MASS: Yes, absolutely. By doing this type of elemental analysis and looking into the pigments that he used and how he used them, we can understand how his working methods changed. And one thing, for example, we see in the 1922 painting versus the 1919 painting is he had introduced the use of titanium white. And so we start to see him using more innovative materials later on in his career.
FLATOW: Fascinating. Thank you very much, Dr. Mass. Good luck to you.
Dr. MASS: Oh, thank you so much, Ira.
FLATOW: You're welcome. Jennifer Mass is the senior scientist at the scientific research and analysis laboratory at the Winterthur Museum, and she's adjunct professor or art conservation at the University of Delaware.
We're going to take a short break, as we normally do, come back and change gears and talk about food. Food's on the mind of a lot of people. Where do the - there - food, have fallacy and fact behind sustainability and what you eat. It's an interesting new book is out, called "Just Food," by James E. McWilliams. He's here to talk about "Where Locavores Get It Wrong and How We can Truly Eat Responsibly." And Michael Pollan's here also to help debate that issue with him, a couple of conflicting opinions.
The debate begins after the break. So come back. We'll be right back. Stay with us.
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FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR News.
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