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The ballpoint pen, explained by David Suzuki

A cup of molasses and a pitcher of water were just two of the props David Suzuki used in 1979 to help viewers understand the science of an everyday implement.

CBC host supplied more than a back-of-the-envelope description of what made the ink flow

On a 1979 episode of the CBC-TV program Science Magazine, host David Suzuki goes into detail about how an everyday item works. 2:35

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.

Suzuki demonstrates the function of a ballpoint pen by signing his own name. (Science Magazine/CBC Archives)

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.

Young Suzuki began hosting CBC Radio's Quirks and Quarks in 1975. (CBC Still Photo Collection)

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."

Hands-on science

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.

The ink in a ballpoint pen didn't flow more easily with heat, but with pressure. (Science Magazine/CBC Archives)

"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.

Suzuki on Science was a 1971 CBC series, hosted by scientist David Suzuki, which examined research and development in science and technology. (CBC Still Photo Collection)