In the Science Lab experiment Viscosity of Liquids we examine the properties of different liquids beginning with a comparison of corn syrup and water. Ketchup becomes thicker, or more viscous, when it sits still. If you stir it up or shake it, it becomes thinner, or less viscous. We see this by dropping weights through ketchup and timing how long they take to sink down to the bottom. We do this first with ketchup that has been sitting still for a while, and then again after the ketchup has been stirred.
Ketchup is a thixotropic liquid.
It becomes less viscous when agitated. Another non-Newtonian liquid is a mixture of cornstarch and water. It also acts differently depending on whether it is still or agitated. But the behavior is the opposite of the way ketchup and Visplex act. You can slowly stick you finger into the cornstarch water mixture and it gives like a liquid, but if you jab it, it feels hard and your finger won't go in very far.