The ballpoint pen, explained by David Suzuki
CBC host supplied more than a back-of-the-envelope description of what made the ink flow
A cup of molasses and a pitcher of water were just two of the props David Suzuki used to help viewers understand the science of an everyday implement: the ballpoint pen.
"It involves a free-rolling ball housed in the socket at the tip ... the ball is about one millimetre in diameter," said Suzuki, host of the CBC-TV program Science Magazine in 1979.
In a kitchen with wood-panel cabinets and brown tile backsplash, Suzuki launched into a detailed explanation about the comparative thickness of liquids like water, molasses and silicone putty.
"The viscosity of these liquids can be altered by changing their temperature," said Suzuki. "But ballpoint pen ink is a different kind of fluid."
Longtime CBC host
Suzuki, a geneticist, has been hosting CBC science programming since 1971, starting with Suzuki on Science on TV and moving to radio for Quirks and Quarks in 1975.
He went back to TV for Science Magazine, which evolved into The Nature of Things in the fall of 1979 and has continued into 2019.
But back to our lesson, conducted by Suzuki wearing a chef's hat and an apron tied at the waist.
Molasses flows more easily once it has been heated, unlike what was inside Suzuki's pen.
"Ballpoint pen ink is a different kind of fluid. It's what's known as a non-Newtonian fluid," he explained. "Viscosity is changed not by temperature but by applying a shearing force."
Suzuki wasn't reluctant to get messy when helping viewers visualize the principles he explained.
He punched his fist into a water-cornstarch mixture in a Pyrex baking dish to demonstrate what a shearing force accomplished.
"When I apply pressure ... to a mixture of cornstarch and water, the viscosity increases," he said.
Ballpoint pen ink worked the opposite way, becoming more viscous when a user pressed the tip to paper.
And it was why the ink stayed in the pen until pressure was applied — its viscosity was greater inside the pen until pressure was applied.
"So as your pen moves across the page, it captures your thoughts, or your signature," said Suzuki.
The property of becoming thinner with pressure made the ink what scientists called "thixotropic."
"So next time you're writing with your ballpoint pen and someone asks you what you're doing, tell them you're decreasing the viscosity of a thixotropic fluid by shearing it," summed up Suzuki.