The Planet on the Table by Kim Stanley Robinson Page B

as Monet has been studied in detail, so that we know he preferred cadmium yellow to chromium yellow or Naples yellow, that he tended to use Prussian blue rather than cobalt blue, and so on.” She tapped the flecks of blue at the base of the cathedral. “Prussian blue.”
    “You’ve taken paint off the canvas?”
    “How else test it? But I took very small samples, I assure you. Whatever the truth concerning the work, it remains a masterpiece, and I would not mar it. Besides, most of my tests were on the white paint, of which there is a great quantity, as you can see.”
    “Why the white paint?” I leaned over to stare more closely at the canvas.
    “Because lead white is one of the best dating tools we have. The manufacturing methods used to make it changed frequently around Monet’s time, and each change in method altered the chemical composition of the paint. After 1870, for instance, the cheaper zinc white was used to adulterate lead white, so there should be over one percent zinc in Monet’s lead white.”
    “And is that what you found?”
    “Yes. The atomic absorption spectrum showed—” She dug around in the pile of chart paper on the table— “Well, take my word for it—”
    “I will.”
    “Nearly twelve percent. And the silver content for late nineteenth century lead white should be around four parts per million, the copper content about sixty parts per million. So it is with this paint. There is no insoluble antimony component, as there would be if the paint had been manufactured after 194.0. The X-ray diffraction pattern”—she unrolled a length of chart paper and showed me where three sharp peaks in a row had been penned by the machine—”is exactly right, and there is the proper balance of polonium 210 and radium 226. That’s very important, by the way, because when lead white is manufactured the radioactive balance of some of its elements is upset, and it takes a good three hundred years for them to decay back to equilibrium. And this paint is indeed back to that equilibrium.”
    “So the paints are Monet’s,” I concluded. “Doesn’t that prove the work authentic?”
    “Perhaps,” Freya admitted. “But as I was doing all this analysis, it occurred to me that a modern forger has just as much information concerning Monet’s palette as I do. With a modern laboratory it would be possible to use such information as a recipe, so to speak, and then to synthesize paints that would match the recipe exactly. Even the radioactively decayed lead white could be arranged, by avoiding the procedures that disrupt the radioactive balance in the first place!”
    “Wouldn’t that be terrifically complicated?”
    Freya stared at me. “
Obviously
, Nathaniel, we are dealing with a very very meticulous faker here. But how else could it be done, in this day and age? Why else do it at all? The complete faker must take care to anticipate every test available, and then in a modern laboratory create the appropriate results for every one of them. It’s admirable!”
    “Assuming there ever was such a forger,” I said dubiously. “It seems to me that what you have actually done here is prove the painting genuine.”
    “I don’t think so.”
    “But even with these paints made by recipe, as you call them, the faker would still have to paint the painting!”
    “Exactly. Conceive the painting, and execute it. It becomes very impressive, I confess.” She walked around the table to look at the work from the correct angle. “I do believe this is one of the
best
of the Rouen cathedral series— astonishing, that a forger would be capable of it.”
    “That brings up another matter,” I said “Doesn’t this work have a five-hundred-year-old pedigree? How could a whole history have been provided for it?”
    “Good question. But I believe I have discovered the way. Let’s go upstairs—you interrupted my preparations for lunch, and I’m hungry.”
    I followed her to her extensive kitchen, and sat in the