music; ambience forensics laboratory, ESDA
JM: You’ve seen the scenario in countless detective movies: the suspect writes a note and tears it off a memo pad. Then the intrepid detective comes along and rubs the side of a pencil on the next page to read the indentation of the hidden message. There’s only one problem – he’s just destroyed the evidence! I’m Jim Metzner and this is the Pulse of the Planet. Forensic document examiner Dwayne Wisbey tells us there’s a high-tech way to read handwriting indentations on that pad of paper. It’s called an ESDA, or electrostatic document apparatus. The first step is to humidify the paper, so that it’ll be more receptive to an electric charge. Then you place it in the ESDA.
DW: We’re going to turn on a pump [click and pump sounds] a vacuum to hold that piece of paper down. And what I’m going to do now is take this piece of mylar, which is kind of like a saran wrap material, and I’m going to pull that over this piece of paper. So this piece of paper will be protected from what I’m about to do to it.
JM: And then Dwayne Wisbey waves a kind of wand over the mylar-covered paper, to apply an electrostatic charge. He’ll spray it with toner, the same kind you’ll find in a copy machine.
DW: The electrostatic charge from the voltage that I’m applying here is different at the sites where the indentations are than the surrounding paper. The toner will be attracted to those indentation locations, and that way we can see it [pump sounds continue]
JM: Toner settles into indentations left on the mystery note, and like magic, the writing appears. And then Dwayne Wisbey preserves it with a sheet of sticky acetate.
Dwayne Wisbey is one of the scientists in this year’s Kids’ Science Challenge, our free nationwide competition for 3rd to 6th graders, made possible by the National Science Foundation, at kidsciencechallenge.com. I’m Jim Metzner.