Listen to part of a lecture in an art conservation class.

M: So far we have been talking all semester about restoring and preserving pieces of art, like ancient frescos, early oil paintings, etc.

But although our field is called art conservation, it also involves… what?

W: Um...preserving other types of cultural materials too.

M: Very good. Not just art. Old artifacts are very valuable when they represent early technologies, all contain important historical information.

In fact, let me give you an example. You've heard about the Greek scholar, Archimedes, who lived more than 2000 years ago, I am sure.

Archimedes was a great mathematician. For example, he discovered the formula for the volume of a sphere.

Not much of his work has survived, but what has survived is brilliant.

And then in 1906, a palimpsest of Archimedes' writing was discovered.

Now, a palimpsest is a type of manuscript that contains writing that's hidden because something else was written over it later.

I'll explain in a minute. This Archimedes palimpsest, as it's now called, is by far the most important palimpsest anyone has ever seen.

Because it contains the only known existing copy of Archimedes' treatise, called Method.

Archimedes shows in it how maths can be applied to physics and physical reasoning back to maths problems, ...

... which is how he calculated the volume of the sphere. For example, this maybe commonplace today, but was revolutionary in his time.

A few years ago, the palimpsest was sold at an auction for 2 million dollars.

It could have ended up tucked away in a private collection, but fortunately, ...

... the collector who bought it has agreed to have experts restore every single word Archimedes wrote, so the contents can be shared with the world and studied.

But there are two main problems. What do you think the first one might be? Jennifer?

W: Um…well, it sounds like it's extremely old. So probably some pages are at the point of crumbling into dust.

M: True. And some are moldy, and some were eaten away at by bookworms.

This thing is really decayed. But on top of that, there's another issue.

And this is the reason why it's a palimpsest.

You see, the text apparently sat around in a library in Constantinople until 1229 A.D.

But then a scribe erased, scraped away the writing as clean as he could in order to use the pages to write his own book on.

Why would he do that? Take a guess.—Must have been a paper shortage?

Well, they used parchment to write on, but yes, there was a parchment shortage.

So you are saying the parchment was basically recycled?—Correct.

Then, even later on, in the twentieth century, a forger painted ancient-looking pictures on several of the pages ...

... in order to make the book seem older and increase its value.

So unfortunately, that's quite a history.

But professor Wilkens, if the scribe scraped away Archimedes' words and if these paintings covered the pages, how can the original work be recovered?

Ah, that's why I am telling you the story. That's our task as conservationists, isn't it?

To find a way. There were still faint traces of Archimedes'words on the pages.

First, we tried to make the Archimedes' words stand out with a variety of technologies, using ultraviolet light.

But that didn't work on every page.

But then, there was this new idea that came from a scientist studying spinach.

Spinach?—Yes. Spinach. This physicist, Uwe Bergman, does research that involves studying iron in spinach.

He was reading an article about problems with the palimpsest and it said that there is iron in the original Archimedes' ink.

So he came up with an idea to use the same method of looking at iron in spinach to view the iron on the palimpsest pages.

And his idea worked. Bergman's technique allows X-rays to pass through the forged paintings, pass through the scribe's writing ...

... to hit the iron traces from the ink of the original Archimedes' text and create an image just of the iron on the pages.

The iron-based letters seem to just pop off the page.

The original text and diagrams emerged, line by line, diagram after diagram.

And that's kind of typical of our field. There's a lot of interdisciplinary work.

ancient frescos   古代壁画

Palimpsest   n. 重写本 写在重写本上的

treatise   n. 论述；论文；专著

parchment   n. 羊皮纸；羊皮纸文稿

faint traces   微弱痕迹

spinach   n. 菠菜

pop off   n. 溢放口 v. 突然离去

emerge   vi. 浮现；摆脱；暴露

interdisciplinary   adj. 各学科间的